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OUTLllSrES OF

PRACTICAL PHYSIOLOGY.

STIRLING'S HISTOLOGY.

SECOND EDITION, REVISED.
368 Illustrations. l2mo. Cloth, net, $2.00.

Outlines of Practical Histology, a Manual for
Students. By William Stirling, m.d., sc.d..
Editor of " Landois' Physiology," author of "Out-
lines of Practical Physiology," etc.

P. BLAKISTON, SON & CO., Philadelphia.

OUTLINES

PRACTICAL PHYSIOLOGY

/IDanual tor tbc pbi^siolooical Xaborator^?,

INCLUDING

CHEMICAL AND EXPERIMENTAL PHYSIOLOGY, WITH
REFERENCE TO PRACTICAL MEDICINE.

WILLIAM STIRLING, M.D., Sc.D.,

BRACKENBURY PROFESSOR OF PHYSIOLOGY 4ND HISTOLOGY IN THE OWENS COLLEGE,

AND PROFESSOR IN VICTORIA UNIVERSITY, MANCHESTER ; EXAMINER IN

PHYSIOLOGY IN THE UNIVERSITIES OF EDINBURGH AND LONDON.

THIRD EDITION, REVISED AND ENLARGED.

IKflitb 289 irilustrations.

PHILADELPHIA:

P. BLAKISTON, SON & CO.,

1012 WALNUT STREET.
1895.

0.

rj.

^n gjemor'iam

CARL LUDWIG,

MY REVERED AND BELOVED MASTER.

Born at Witzenhausen, 29th December, ISltti
*}iED AT Leipzig, 23rd April, 1895.

PREFACE TO THE THIRD EDITION.

In the light of extended experience in teaching Practical
Physiology, I venture to submit a Third Edition of this little
work. The essential features remain unchanged; but there has
been some re-arrangement of the subject-matter, and many addi-
tions have been made, including a short Appendix on Recording
Apparatus.

In preparing the Chemical Part, I have made use of the Text-
books of Gamgee, Halliburton, Neumeister, and Salkowski ; while,
for the Experimental Part, I found numerous valuable suggestions
in the practical works and syllabuses of my friends, Professors
Gotch, HaUiburton, Fredericq, and Dr Schenk, I have to express
my thanks to Professor Pick of Wurzburg for several improvements
in the Lessons on Muscle.

A large number of new woodcuts have been added (chiefly in the
Experimental Part) ; and for communications and several original
drawings — some of the latter illustrating new metliods described
by their authors — I am indebted to my friends and colleagues,

vi PREFACE.

Professors Birch, Gotch, Rutherford, and Schafer, Dr Bayliss, Dr
Gregor Brodie, and C. Herbert Hurst, Ph.D. The sources of the
other illustrations and methods are acknowledged elsewhere.

I have also to thank my pupils, IMessrs Moore, Halstead, and
J, H. Sheldon, for some of the drawings, and my Senior
Demonstrator, Dr J. A. Menzies, for reading the proof sheets, and
for other kind assistance and suggestions.

WILLIAM STIELING.

Physiological Laboratory, Owens Collbob,
Makchestek, August 1895.

CONTENTS.

USSON

I.
II.

m.

IV.
V.
VI.

VIII.
IX.
X.
XI.

xn.

XIII.
XIV.
XV.
XVI.

xvn.
xvin.

XIX.

XX.

XXI.

XXII.

xxm.

XXIV.

PAET I.— CHEMICAL PHYSIOLOGY.

PAGES

THE PROTEIDS I-I2

THE ALBUMENOIDS AND SOME NITROGENOUS DERIVATIVES OF

PROTEIDS 13-14

THE CARBOHYDRATES 1 5-29

FATS, BONE, AND EXERCISES 29-33

THE BLOOD — COAGULATION — ITS PROTEIDS .... 33-43
THE COLOURED BLOOD-CORPUSCLES— SPECTRA OF H.EMOGLOBIN

AND ITS COMPOUNDS 43-55

WAVE-LENGTHS — DERIVATIVES OF HEMOGLOBIN — ESTIMATION

OF H.EMOGLOBIN 55-6?

SALIVARY DIGESTION 67-7 1

GASTRIC DIGESTION 71-79

PANCREATIC DIGESTION 79-86

THE BILE 87-90

GLYCOGEN IN THE LIVER 91-94

MILK, FLOCK, AND BREAD 94-99

MUSCLE 99-103

SOME IMPORTANT ORGANIC SUBSTANCES IO3-IO4

THE URINE IO4-IIO

THE INORGANIC CONSTITUENTS OF THE URINE .... IIO-Il6

ORGANIC CONSTITUENTS OF THE URINE II7-120

VOLUMETRIC ANALYSIS FOR UREA I20-127

URIC ACID— URATES — HIPPURIC ACID — KREATININ . . . I27-I36

ABNORMAL CONSTITUENTS OF THE URINE I36-I39

BLOOD, BILE, AND SUGAR IN URINE I4O-I43

QUANTITATIVE ESTIMATION OF SUGAR I43-I47

URINARY DEPOSITS, CALCULI, GENERAL EXAMINATION OF THE

URINE, AND APPENDIX 147-155

vm CONTENTS.

PART II.— EXPERIMENTAL PHYSIOLOGY.

I.ESSOS PAGES

XXV. GALVAXrC BATTERIES AND GALVANOSCOPB .... 157-160

XXVI. ELECTRICAL KEYS— RHEOCHORD l6o-l66

XXVII. INDUCTION MACHINES — ELECTRODES 166-17O

XXVIII. SINGLE INDUCTION SHOCKS— INTERRUPTED CURRENT— BREAK

EXTRA-CURRENT — HELMHOLTZ'S MODIFICATION . . . 17I-I76

XXIX. PITHING — CILIARY MOTION — NERVE-MUSCLE PREPARATION —

NORMAL SALINE I76-I79

XXX. NERVE-MUSCLE PREPARATION — STIMULATION OF NERVE —

MECHANICAL, CHEMICAL, AND THERMAL STIMULI . . . I79-183
XXXI. SINGLE AND INTERRUPTED INDUCTION SHOCKS — TETANUS-
CONSTANT CURRENT 183-187

XXXII. RHEONOM — TELEPHONE EXPERIMENT— DIRECT AND INDIRECT
STIMULATION OF MUSCLE — RUPTURING STRAIN OF TENDON —
MUSCLE SOUND— DYNAMOMETERS 187-189

XXXIII. INDEPENDENT MUSCULAR EXCITABILITY— ACTION OF CURARE —

ROSENTHAL'S MODIFICATION— POHL'S CO.MMUTATOR . . 190-194

XXXIV. THE GRAPHIC METHOD — MOIST CHAMBER — SINGLE CONTRACTION

— WORK DONE 194-200

XXXV. CRANK-MYOGRAPH — AUTOMATIC BREAK 2OO-203

XXXVI. ISOTONIC AND ISOMETRIC CONTRACTIONS —WORK DONE — HEAT-
RIGOR ........... 203-206

XXXVII. PENDIJLUM-MYOGRAPH — SPHING-MYOGRAPH — TIME-MARKER —

SIGNAL ........... 206-213

XXXVIII. INFLUENCE OF TEMPERATURE, LOAD, AND VERATRIA ON

MUSCULAR CONTRACTION 213-216

XXXIX. ELASTICITY AND EXTENSIBILITY OF MUSCLE— BLIX'S MYOGRAPH 2l6-2l8

XL. TWO SUCCESSIVE SHOCKS— TETANUS 219-223

XLI. FATIGUE OF MUSCLE 223-224

XLIL FATIGUE OF NERVE —SEAT OF EXHAUSTION .... 225-226
XLIII. MUSCLE WAVE- -THICKENING OF A MUSCLE- WILD'S APPARATUS 226-229
XLIV. MYOGRAPHIC EXPERIMENTS ON MAN — ERGOGRAPH — DYNAMO-
GRAPH 229-231

XLV. DIFFERENTIAL ASTATIC GALVANOMETER — NON-POLARISABLE

ELECTRODES — SHUNT — CURRENTS IN MUSCLE .... 231-237
XLVI. NERVE-CURRENTS — ELECTRO-MOTIVE PHENOMEN.\ OF THE HEART

— CAPILLARY ELECTROMETER 237-238

XLVn. <: M.VANl'S EXPERIMENT — SECONDARY CONTRACTION AND TETANUS

—PARADOXICAL CONTRACTION— KUHNE'S EXPERIMENT . . 239-243

XLVIII. ELECTROTONUS— ELEQTROTONIU VARIATION OF EXCITABILITY , 243-247

CONTENTS. IX

LKSSOtf PAOES

XLIX. PFLOGER's law of contraction — ELECTROTONIC VARIATION OF

THE ELKCTRO-MOTIVITY — hitter's TETANUS .... 247-25O
L. VELOCITY OF NERVE-IMPULSE IN MOTOR NERVES OF FROG AND

MAN — KUHNE'S gracilis EXPERIMENT 250-254

LI. CONDITIONS AFFECTING EXCITABILITY OF NERVE . . . 254-258

LII. THE FROG'S HEART — BEATING OF THE HEART — EFFECT OF HEAT

AND COLD — SECTION OF THE HEART 259-262

mi. GRAPHIC RECORD OF THE FROG'S HEART-BEAT — EFFECT OF

TEMPERATURE 262-265

LIV. SUSPENSION METHODS FOR HEART — GASKELL'S HEART-LEVER

AND CLAMP 266-270

LV. STANNIUS'S EXPERIMENT ^ INHIBITION — LATENT PERIOD OF

HEART-MUSCLE 270-273

LVI. CARDIAC VAGUS AND SYMPATHETIO OF THE FROG AND THEIR

STIMULATION 273-276

LVII. ACTION OF DRUGS AND CONSTANT CURRENT ON HEART — DESTRUC-
TION OF CENTRAL NERVOUS SYSTEM 277-279

LVIII. PERFUSION OF FLUIDS THROUGH THE HEART — PISTON-RECORDER 279-281
LIX. ENDOCARDIAL PRESSURE — APEX-PREPARATION — TONOMETER . 281-284
LX. HEART-VALVES — ILLUMINATED HEART — STETHOSCOPE — CARDIO-
GRAPH—POLYGRAPH—INHIBITION OF HEART .... 284-291

LXI. THE PULSE — SPHYGMOGRAPHS — SPHYGMOSCOPE — PLETHYSMO-

6RAPH ..... ...... 291-295

LXU. RIGID AND ELASTIC TUBES — THE PULSE-WAVB — SCHEME OF THE

CIRCULATION — RHEOMETER .... . . 295-30O

L.XIII. CAPILLARY BLOOD-PRESSURE— LYMPH HEARTS — BLOOD-PRESSURE

AND KYMOGRAPH . . . 300-306

LXIV. PERFUSION THROUGH BLOOD-VESSELS 306-307

LXV. MOVEMENTS OF THE CHEST WALL — ELASTICITY OF THE LUNGS-
HYDROSTATIC TEST 308-311

LXVL VITAL CAPACITY — EXPIRED AIR— PLEURAL PRESSURE- GASES

OF BLOOD AND AIR 311-314

LXVII. LARYNGOSCOPE — VOWELS 315-317

LXVIII. REFLEX ACTION—ACTION OF POISONS — KNEE-JERK . . . 318-322

LXIX. SPINAL NERVE ROOTS 322

LXX. REACTION TIME — CEREBRAL HEMISPHERES .... 323-328

LXXI. FORMATION OF AN IMAGE — DIFFUSION — ABERRATION — ACCOM-
MOD.\TION — SCHEINER'S EXPERIMENT — NEAR AND FAR
POINTS- PURKINJE'S IMAGES — PHAKOSCOPE — ASTIGMATISM —

PDPIL 329-337

LXXII. BLIND SPOT — FOVEA CENTRALIS— DIRECT VISION — CLERK-MAX-

WELL'S experiment— PHOSPHENES— RETINAL SHADOWS . 337-343

IvXXin. PERIMETRY — IRRADIATION — IMPERFECT VISUAL JUDGMENTS . 344-350

CONTENTS.

PAOBS

LESSOR

LXXrV. KiJHNB'S ARTIFICIAL EYE— MIXING COLOUR SENSATIONS— COLOUR

BLINDNESS 350-3^3

LXXV. THE OPHTHALMOSCOPE — INTRAOCULAR PRESSURE— OPHTHALMO-
TONOMETER • • 364-367

UtXVI TOUCH, SMELL, TASTE, HEARING 3^7-372

APPKSDtS. 373

/Tn}BX

392

LIST OF ILLUSTRATIONS.

12.

13-
14.

IS-
16.

17-
18.
19.
20.
21.
22.

23-
24.

25-
26.
27.
28.
29.
30-
31-
32-
33-
34-
35-
36.
37-
38.
39-

Apparatus for coagnlation temperature. (Gam/iee.)
Apparatus for fractional heat coagulation. {Halliburton.)
Potato starch ........

Potato starch viewed with crossed Nicols. (Stirling.)
Dextrose. (Hill.) .......

Phenyl-glucosazon. (Stirling.) ....

Maltose. (Hill.)

Phenyl-maltosazon. (Stirling.) ....

Lactose. (Hill.) .......

Phenyl-lactosazon. (Stirling.) ....

Cane sugar. (Hill.)

Laurent's polarimeter. (Laurent.) ....

Wild's polaristrobometer. (Hermann and Pfister.) .
Interference lines, seen with fig. 13 .
Gad's experiment. (Stirling, after Gad.) .
Exsiccator. (Gscheidlen.) .....

Apparatus for obtaining clear serum. (Drechsel.)
Bernard's apparatus for estimating sugar. (Stirling.)
Incineration of a deposit. (Gscheidlen.) ...
Gower's hsemocytometer ......

Rat's hsemoglobin crystals. (Stirling.)
Spectroscoiie. (Bro^iming.) .....

Platinum wire support for sodium flame. (Gscheidlen.)

Spectra of hsemoglobin. (Landois and Stirling.)

Absorption by oxy-ha!inoglobin. (Rollett.)

Absorption by reduced hseinoglobin. (Rollett.) .

Hermann's haematoscope. (Ro/lett.)

Spectra of derivatives of haemoglobin. (Landois and Stirling.)

Haemochromogen apparatus. (Stirling.) .

Spectrum of metlu-emoglobin. (V. Ja/csch.)

Spectroscope for wave-lengths. (Landois and Stirling.)

Wave lengths of hfemoglobin and its compounds. (Prci/er and Uaingee.

Spectra of derivatives of hsemoglobin
Haemin crystals. ( V. Jaksch. )
Haemoglobinometer of Cowers
Fleischl's haemometer
Bizzozero's chromo-cytomcter
Several parts of fig. 37
Micro-spectroscope of Zeiss

(Pr

eyer and Gam gee.)

23
23
24
24
24
26

27
28

30
40

41
42

43
44
45
46
46
47

50
51
52
52
55
) 57
58
59
60
6i
62

63
66

xu

LIST OF ILLUSTRATIONS.

FIG.

40. Part of fig. 39. {Zeiss. ) .

41. Saliva and buccal secretion. (V. Jaksch.)

42. Digestion bath. (Stirling.)

43. Kiihne's dialyser. {Stirling.) .

44. Crystals of tyrosin. {Stirling.)

45. T'rystals of cholesterin. (Stirling.) .

46. Double-walled funnel. {Gscheidkn.)

47. Hot air-oven. (Gscheidlen.)

48. Milk and colostrum. {Stirling.)

49. Porous cell for filtering milk. {Stirling. )

50. Lactoscope .....

51. Kreatin. {Brunton.)

52. Urinometer. {Landois and Stirling.)

53. Dejiosit in acid urine. (Landois and Stirling.)

54. Deposit in alkaline urine. (Landois and Stirling.)

55. Stellar phosphate. (V. Jaksch.)

56. Triple phosphate

57. Triple phosphate. {V. Jaksch.)

58. Burette meniscus

59. Erdmann's float

60. Urea and urea nitrate. (Landois and Stirling.)

61. Urea oxalate ......

62. Dupre's urea apparatus ....

63. Steele's apparatus for urea

64. Ureameter of Doremus. (Southall.)

65. Hiif ner's apparatus. ( V. Jaksch. )

66. Gerard's urea apparatus. (Gibhs, Ouxson d; Co.

67. Uric acid ......

68. Uric acid ......

69. Hippuric acid. (Landois and Stirling.)

70. Kreatinin zinc-chloride. (Landois and Stirling.

71. Esbach's tube. (V. Jaksch.)

72. Johnson's picro-saccharimeter

73. Einhorn's fermentation saccharometer. (Stirling.)

74. Sacchar-ureameter. (Gihbs, Cuxson <£• Co.)

75. Hand centrifuge. (Muencke.)

76. Oxalate of lime

77. Acid urate of ammonium. (V.

78. Pystin ....

79. Leucin and tyrosin .

80. Daniell's cell. (Stirling. )

81. Grove's cell

82. Bichromate cell

83. Detector. (Ellio't.)

84. Du Bois Reymond's key

85. Scheme of 84. (Stirling. )

86. Scheme of 84. (Stirling.)

87. Morse key. (Stcu-art and Gee.)

88. Spring key. (Elliott.)

89. Plug key ....

Jaksch. )

LIST OF ILLUSTRATIONS.

Xlll

no.

90. Simple rheochord. (Stirling.) ....

91. Simple rheochord. {Stirling.} ....

92. Rheochord, Oxford pattern. (Stirling.) .

93. Reverser. (Elliott.) ......

94. Dii Bois Raymond induction coil. (Elliott.)

95. Ewald's sledge coil. (Hurst.) ....

96. Vertical inductorium .....

97. Hand-electrodes. (Stirling.) ....

98. Du Bois electrodes ......

99. Induction coil for single shocks. (Stirling.)
100. Du Bois coil .......

lor. Break extra-current. (Stirling.)

102. Helmholtz's modification .....

103. Equalised make and break shocks. (Stirling.) .

104. Brodie's rotating key ......

105. Frog's leg-rausclea. (Ecker.) ....

106. Frog's sciatic nerve. (Ecker.) ....

107. Nerve-muscle preparation .....

108. Straw-flag. (Stirling.) .....

109. Scheme for single induction shocks. (Stirling.)

1 10. Scheme of constant current. (Stirling. ) .

111. Frog's sartorius and thigh muscles. (Ecker.)

112. Rheonom. (Stirling.) .....

113. Pohl's commutator. (Elliott.) ....

114. Scheme of curare experiment ....

115. Revolving cylinder of Ludwig ....

116. Scheme of moist chamber. (Stirling.)

117. Record of make and break contractions. (Stirling.

118. Muscle curve. (Stirling ) ....

119. Crank myograph. (Stirling.) ....

120. Arrangement for automatic break. {Stirling.) .

121. Simple muscle curve. (Stirling.)

122. Isotonic and isometric muscle curves. (Gad.) .

123. Scheme of Fick's tension recorder. (Schenk.)

124. Apparatus for heat rigor. (Ludwig.)

125. Pendulum -myograph .....

126. Pendulum-myograph curve. (Stirling.)

127. Spring-myograph ......

128. Revolving drum for time relations of muscle curve

129. Electric signal. (Stirling.) ....

130. Chronograph. (.Cambridge Scientific Instrument Co.)

131. Chronograph writing horizoni ally. (Marey.)

132. Simple myograph. (Marey.) ....

133. Myograph. (Fredericq.) .....

134. Effect of temperature on muscle curve. (Stirling.)

135. Muscle curve with load. (Stirling.) .

136. Veratria curve. (Stirling. ) . . . .

137. Veratria curve. (Stirling.) ....

138. Elasticity of a frog's muscle. (Stirling.) .

139. Elasticity of india-rubber. {Stirling. ) . .

XIV

LIST OF ILLUSTRATIONS.

FIO.

140. Blix's myograph. (Fick.) ....

141. Curve of superposed contractions. {Stirling )

142. Scheme for tetanus. [Stirling.)

143. Tetanus (incomplete) curves. (Stirling. ) .

144. Tetanus interrupter. [Stirling.)

145. Metronome. [Petzold.)

146. Magnetic interrupter. [Cambridge Scientific Instrv/meni Co.)

147. Fatigue curve. [Stirling.)

148. Fatigue curve, slow di-um. [Stirling.

149. Muscle wave apparatus

150. Marey's registering tambour

151. Pince myographique. [Marey.)

152. Wild's apparatus. [Stirling.) .

153. Fick's tension myograph. [Schenk. )

154. Mosso's ergograph

155. Thomson's galvanometer. (Elliott.)

156. Lamp and scale for 155

157. Non-polarisable electrodes

158. Shunt. [Elliott.)

159. Scheme for galvanometer. (Stirling.)

160. Brush electrodes. (V. FleischL)
161 D'Arsonval's electrodes. (Verdin.)

162. Non-i)olarisable nerve electrodes

163. Galvani's experiment. (Stirling. )

164. Secondary contraction .....

165. Scheme of secondary contraction. (Stirling.) .

166. Scheme of paradoxical contraction. [Stirling.) .

167. Kiihne's experiment. [Stirling.)

168. Scheme of electrotonic excitability. [Stirling.)

169. Scheme of electrotonus. (Stirling.) .

170. Curve of electrotonus. [Stirling.)

171. Scheme of electrotonus. (La)idois and Stirling.)

172. Pohl's commutator with cross-bars

173. Scheme of Pfliiger's law of contraction. (Stirling.)

174. Scheme for kathodic stimulation

175. Du Bois Reymond's rheochord ....

176. Scheme of velocity of nerve-energy. [Stirling.)

177. Kuhne's gr.icilis experiment. [Stirling.) .

178. Scheme for unequal excitability of a nerve. [Stirling.]

179. Scheme for Griinhagen's experiment

180. Frog's heart from the front. [Erker.

181. Frog's heart from behind. [Ecker )

182. Simple frog's heart lever .

183. Tracing of frog's heart. [Stirling.)

184. Effect of temperature on frog's heart tracing. [Stirling.)

185. Marey's heart lever .

186. Francois- Frank's lever for heart of tortoise. [Verdin)

187. Gaskell's lever. [Stirling.) ....

188. Tracing of frog's heart taken with 186. [Stirling.)

189. Heart-tracing, varying speed of drum. [Stirling.)

LIST OF ILLUSTRATIONS.

XV

FIO.

190. Heart-tracing, effect of heat and cold. (Stirling.)

191. Gaskell's clamp. {Stirling}. ) . . .

192. Tracing of auricles and ventricle. (Stirling.)

193. Gotch 'a arrangement for excised heart. (Stirling.)

194. Tracing inhibition of heart. (Stirling. )

195. Latent period of vagus. (Stirling. ) .

196. Scheme of frog's vagus. (Stirliru/.) .

197. Vagus curve of frog's heart. (Stirling.)

198. Scheme of frog's sympathetic. (Gaskell.)

199. Effect of muscarine and atropine on the heart. (Stirling. )

200. Support for frog's heart. (Stirling. ) .

201. Staircase heart-tracing ....

202. Kronecker's frog's heart cannula

203. Heart-tracing during perfusion. (Stirling.)

204. Scheme of Kjonecker's manometer. (Stirling.)

205. Scheme of Roy's tonometer. (Stirling.) .

206. Tonometer. (Carnhridge Scientific Instrument Co.

207. Illuminated ox-heart. (Frrrhrir'/ nffrr Gad.)

208. Marey's cardiograph ....

209. Polygraph of Rothe ....

210. Cardiac impulse tracing. (KnoU.)

211. Kothe's tambour ....

212. Radial pulse and respirations. (Knoll. )

213. Radial pulse and cardiac impulse. (Knoll.

214. Marey's sphygmograph. iBramwell.)

215. Sphygmograms. (Mareij.)

216. Dudgeon's sphygmograph .

217. Sphygmogram. (Dudgeon.)

218. Ludwig's sphygmograph

219. Arm support for 217 '

220. Gas-sphygmoscope ....

221. Marey's scheme of rigid and elastic tubes

222. Rheometer .....

223. Capillary pressure apparatus (F. Kries.)

224. Lymph-hearts. (Ecker.) .

225. Simple kymograph (made by Verdi n.)

226. Nerves in neck of rabbit. (Ci/on.)

227. Shielded electrodes as made by Vcrdin

228. Blood-pressure tracing of dog

229. Blood pressure tracing of dog. (Stirling.)

230. Francois-Frank's cannula. (Verdin.)

231. Marey's respiration double tambour .

232. Stethographic tracing. (Stirling.)

233. Marey's stethograph (Ferdm.) .

234. Stethographic tracing. (Knoll. )

235. Miiller's valves. (Stirling.)

236. Heywood's experiment. (Stirling.) .

237. Gases collected over mercury. (Gscheidlen.

238. Hempel's apparatus for expired air .

239. Hempel's absorjttion pipette . .

XVI

LIST OF ILLUSTRATIONS.

KG.

240. View of larynx

241. Larynx during vocalisation

242. Konig's apparatus

243. Reaction time, pendulum method. {Huther/oi-d

244. Kesult obtained with 243. {Rutherford.)

245. Reaction time for touch, sight, hearing. (Rutherfwd

246. Reaction time. (Stirling.)

247. Neuramcbbimeter. (Obersteiner.)

248. Frog's brain. (Landois and Stirling.)

249. Scheiner's experiment ....

250. Diffusion. (HelmhoUz.) ....

251. Phakoscope ......

252. Model of plates of ophthalmometer. (Auher.

253. Apparatus for vision of a point. (Ludwig.)

254. Mariotte's experiment ....

255. Mariotte's experiment (another way)

256. Blind spot. [Hdmholtz. ) .

257. Volkmann's experiment on the blind spot

258. Bergmann's experiment. (HelmhoUz.)

259. Disc for Talbot's law. (HelmhoUz.)

260. Charpentier's disc for " black band '

261. Charpentier's disc for coloured field

262. Priestley Smith's perimeter

263. Scheme for wheel movements of eye. (Heriny.

264. Irradiation. (HelmlwUz.)

265. Irradiation. (HelmhoUz.)

266. Irradiation. (HelmhoUz.)

267. Imperfect visual judgments of letters

268. ZoUner's lines ....

269. Imperfect visual judgment of size

270. Perception of size. (HelmhoUz. )

271. Spiral disc for radial movement. {HelmhoUz.)

272. Kiihne's artificial eye, as made by Jung

273. Apparatus to mix coloured light. (Hering.)

274. Scheme of 273. (Hering.)

275. Rothe's rotatory apparatus

276. Disc for contrast. (HelmhoUz.)

277. Disc for simultaneous contrast. (HelmhoUz.)

278. Ragona Scina's experiment. (Mood.)

279. Hering's apparatus for 278. (Hering.)

280. Apparatus for simultaneous contrast. (Hering.

281. Simultaneous contrast apparatus. (Hering)

282. Bird and cage experiment

283. Spectrum top. (Hurst.) . • . .

284. Spectrum top with spiral. (Hurst.) ,

285. Michel's carriage for rabbit. (Stirling.)

286. Priestley Smith's demonstrating ophthalmoscopy

287. Aristotle's experiment

288. Sherrington's drum as made by Palmer

289. Birch's drum and recording apparatus. (Birch.)

PRACTICAL PHYSIOLOGY.

PART L~CHEMICAL PHYSIOLOGY.

LESSON I.
THE PROTEIDS.

As a type of the group of proteids we may take white of egg, egg-
white, or egg-albumin. In nature they occur only as constituents
or products of living organisms. In animals they form the prin-
cipal soUds of the muscular, nervous, and glandular tissues of
hlood-serum and lymph. The bile, urine, tears, and sweat, are the
only animal fluids which normally do not contain proteids. Their
elementary composition varies within the following limits : —

c.

H.

N.

0.

s.

From 50

6.8

15.0

22.8

0.4 per cent.

To 55

7.3

18.2

24.1

5-0 „

They are amorphous, and for the most part colloid bodies. They
possess certain chemical reactions in common, and are closely
related to each other. They are insoluble in alcohol and ether,
some are soluble in water, otliers insoluble, while others are soluble
in weak saline solutions. Tliey all rotate the ray of polarised light
to the left, and are thus Isevorotatoiy. In strong acids and alkalies
they are dissolved, but they mostly undergo decomposition in the
process. AVhen decomposed, they yield a very large number of other
bodies, so that tlieir constitution is exceedingly complex. In the
body, after undergoing a series of metabolic changes, they are ex-
creted chiefly in the form of urea, and a number of more or less
closely related nitrogenous bodies. Besides the general characters
stated below, most of them yield aromatic bodies, such as tyrosin
and phenol.

2 PRACTICAL PHYSIOLOGY. [l.

1. Preparation of a Solution of Egg-Albvimin— Soluble in
Water. — Place the unboiled white of an egg in a porcelain capsule
(taking care that none of the yolk escapes), and cut it freely many
times with scissors to disintegrate the membranes, and thus liberate
the albumin. Add twenty volumes of distilled water, shake the
mixture vigorously in a flask until it froths freely. Cork the flask
and invert it, mouth downwards, over a porcelain capsule ; the
froth and dehris float to the surface, and, after a time, if the
cork be gently withdra^vn to allow the fluid to escape, a sUghtly
opalescent fluid is obtained. The opalescence is due to the pre-
cipitation of a small quantity of globuhns. If the fluid be too
opalescent, strain through flannel or several folds of muslin. Such
a solution filters slowly, so that it is better to employ several small
filters if a clearer solution be required. If the fluid be alkahne,
neutralise it with 2 per cent, acetic acid. Egg-white contains about
11-12 per cent, of egg-albumin, together with small quantities of
globuhns, grape-sugar, and mineral matter.

General Reactions. — (A.) Colour Reactions.

(rt.) Xanthoproteic Reaction. — Add strong nitric acid = a
white precipitate, which on being boiled turns yellow. After cool-
ing add ammonia = the yellow colour or precipitate becomes orange.

{h.) Millon's Test = a whitish precipitate which becomes brick-
red on boihng. A red colour of the fluid is obtained if only a
trace of proteid be present.

Preparation of Millon's Reagent. — Dissolve mercury in its own weight of
strong nitric acid, specific gravity 1.4, and to the solution thus obtained add
two volumes of water. Allow it to stand, and afterwards decant the clear
fluid ; or take one part of mercury, add two parts nitric acid, specific gravity
1.4 in the cold, and heat over a water-bath till complete solution occurs.
Dilute with two volumes of water, and decant the clear fluid after twelve
hours.

{e.) Piotrowski's Reaction. — Add excess of strong solution of
caustic soda (or potash), and then a drop or two of very diluic. solu-
tion of cupric sulphate (1 per cent.) = a vinlet colour. The reaction
occurs more quickly if heat is applied, and tlie colour deepens.

The peptones and albumoses give a rose-pink colour, instead of a
violet, if only a trace of copper sulphate is used.

(B.) Precipitation. — Peptones and albumoses are excejjtions in
many cases.

{(l.) The solution is precipitated by (i.) lead acetate; (ii.) mer-
curic chloride ; (iii ) picric acid ; (iv.) strong acids, ^^r/., nitric ; (v.)
tannin ; (vi.) alcohol.

{e.) ^lake a portion strongly acid Avith acetic acid, and add
potassic ferrocyanide = a white precipitate.

(/.) Saturate it with aramouium sulphate by adding crystals of

I.] THE PROTEIDS, 3

the salt, and shaking vigorously in a tube or flask. This precfpi-
tates all proteids except peptones. Filter ; the filtrate contains no
proteids.

ig.) By hydrochloric acid in a solution saturated with common salt.

(h.) By alcohol, except in the presence of a free alkali.

(i.) Precipitate a portion with (i. ) meta-phosphoric acid ; (ii. ) ])hosphotung-
stic acid, after acidulating with HCl.

N.Ii. — Peptones are not precipitated by (''.) and (/'.),

(C.) Coagulation by Heat.

(./.) Heat the fluid to boiling — there is no coagulum of albumin'
formed — and then add, drop by drop, dilute acetic acid (2 per
cent.), until a flaky coagulum of coagulated insoluble albumin
separates.

The coagulum comes down about 70° C. Unless the fluid
be acidulated, the albumin does not coagulate.

(/>.) Boil and add nitric acid = a white or yellowish coagulum.

(/.) Acidify strongly with acetic acid, add an equal volume of
a saturated solution of sodic sulphate, and boil = coagulation.
This precipitates all proteids except peptones. This method and
the foregoiug (J.) are used for separating the albumin in a liquid
containing it.

(D.) (m.) Indiffusibility. — Place some of the solution either m
a dialyser or in a sausage-tube made of parchment-paper, and sus-
pend the latter by means of a glass rod thrust through the tube
just below the two open ends (Lesson IX.) in a tall glass jar idled
with distilled water, so that the two open ends are above the sur-
face of the water. The salts (crystalloids) difluse readily (test for
chlorides by nitrate of silver and nitric acid), but on applying any
of the above tests no proteids are found in the dift'usate. They
belong to tlie group of Colloid bodies. (Peptones, however, are
diftusible through animal membranes.)

(E. ) (n.) Reaction of Adamkiewicz. — To white of egg add glacial acetic
acid, and heat to get it in solution; gradually add concentrated suliihuiic
acid = a violet colour with slight fluorescence.

(0.) Liebermann's Reaction. — Wash tinely powdered albumin first with
alcohol and then with cold ether, and heat the washed residue Mitli concen-
trated hydrocliloric acid = a deeji violet-blue colour. This is best done in a
white porcelain ca]>sule, or on a filter- pa jier in a funnel ; in the latter case,
the boiling acid is poured gently down the side of the iilter-jiajier.

For other colour reactions with cobalt sulphate and NH4HO, and KHO see
Pickering, Journ. of Phys., vol. xiv.

2. Presence of Nitrogen and Sulphur in Albumin.

(rt.) Place some powdered dried albumin in a reduction tube,
and into the moutli of the tube insert (i) a red litnuis paper,
and (2) a lead acetate paper. On heating the tube, the former
becomes blue from the escape of ammonia, which can also be

PRACTICAL PHYSIOLOGY.

[I.

smelt (odour of burned feathers), and the latter black from the
formation of lead sulphide.

(b.) Heat some dry proteid with excess of soda-lime in a hard
dry tube ; ammonia vapour is evolved.

{c.) Place a few grains of the dry pioteid, with a
small piece of metallic sodium, in a dry hard tube,
and heat slowly at first, and then strongly. After
cooling, add carefully 3 cc. of water to the NaCy
residue, filter, and to the filtrate add a few drops of
ferric chloride and ferrous sulphate, and then add
excess of hydrochloric acid. If nitrogen be present,
there is a precipitate of Berlin blue, sometimes only
seen after standing for a time.

(d.) To a solution of albumin add an equal volume
of solution of caustic potash and a few drops of lead
acetate and boil for some time = slowly a brownish
colouration, due to lead sulphide.

3. Determination of Temperature of Coagulation

(fig. i). — The reaction of the fluid must be neutral
or feebly acid. "A glass beaker containing water
is placed within a second larger beaker also contain-
ing water, the two being sejiarated by a ring of cork.
Into the water contained in the inner beaker there
is immersed a test-tube, in which is fixed an accurately
graduated thermometer, j)rovided with a long narrow
bulb. The solution of the proteid, of which the
tem])erature of coagulation is to be determined, is
placed in the test-tube, the quantity being just
sufficient to cover the thermometer bulb. The whole
Fig. I.— Apparatus for De- ap])aratus is then gradually heated, and the experi-
terniinin.i; the Coagula- menter notes the temperature at which the liquid first
tion Teninerature of 1 • c t jj //y \

Proteids .shows signs of opalescence ((r«?i(j/ff).

4. Circumstances Modifying the Coagulating Temperature. — Place 5 cc.
of the solution of albumin in each of three test-tubes, colour them with a
neutral .solution of litmus, and label them A, B, C. To A add a droj) of very
dilute acetic acid ( ). i ])er cent, acetic acid diluted five or six times); to B
add a very dilute .solution of caustic soda (o. i ])er cent, of soda or potash
similarly diluted); C is neutral for comparison. Place all three tubes in a
beaker with water and heat them gradually, noting that coagulation occurs
first in A, next in C, and not at all in B, the alkaline solution.

CLA.SSIFICATION OF PROTEIDS.

5. I. Native Albumins are soluble in vxder, in dilute saline
solution.s, in saturated solutions of sodic chloride, and magnesium
sulphate, and are not precipitated by alkaline carbonates, sodic
chloride, or very dilute acids. They are precipitated by saturating
their solutions with ammonium sulphate. These solutions are
coagidated by heat at 70° to 73° C, although the temperature

I.] THE PROTEIDS. 5

varies considerably with a large number of conditions. "When
dried at 40° C. they yield a clear yellow coloured mass, " soluble
albumin," which is soluble in water.

(i.) Egg. Albumin. — Prepare a solution (Lesson I. 1.).

(a. ) Evaporate some of the fluid to dryness at 40' C. over a water-bath to
obtain "soluble albumin." Study its characters, notably its solubility in
water. This solution gives all the tests of egg-albumin. It is more con-
venient to purchase this substance,

(h.) The fluid gives all the general proteid reactions.

(c.) Precipitate portions of the fluid with strong mineral acids,
including sulphuric and In'drochloric acids.

('/.) Precipitate other portions by each of the following : — ^ler-
curic chloride, basic lead acetate, tannic acid, alcohol, picric acid.

(''.) Take 5 cc. of the fluid, add twice its volume of o.i per cent,
sulphuric acid, and then add ether. Shake briskly = coagulation
after a time, at the line of junction of the fluids.

(/.) The solution is 7iot precipitafed on saturation with crystals
of sodic chloride or magnesic sulphate, but it is completely pre-
cipitated on saturation with ammonium sulphate (XH^)^804 (com-
pare " Globulins ").

{;/.) A solution containing 1-3 per cent, of salts coagulates at
about 56° C.

(2.) Serum Albumin. — Blood-serum (see "Blood") contains
serum-albuniiu and serum-globulin. Dilute blood-serum until it
has the same specific gravity as the egg-albumin solution. A slight
opalescence, due to precipitation of serum-globulin, is obtained.
Neutralise the solution with very dilute acid until a faint haziness
is obtained.

Repeat the tests for egg-albumin, and, in addition, with undiluted
blood-serum.

(//.) Add crystals of MgSO^ to saturation, .shaking the fla.sk
vigorously to do so = a white precipitate of serum-globuhn. Filter.
The filtrate contains serum-allmmin.

(z.) .Saturate serum witli (XH^).,S04 = white precipitate of both
serum-albumin and serum-globulin. Filter. The filtrate contains
no proteids.

EGO-ALBUMIN. SERUM-ALBUMIN.

(i.) Readily precipitated by (i.) It is also precipitated by

hydrochloric aciil, but the pre- hydrochloric acid, but not so

cipitate is not readily soluljle in readily, wliile the precipitate is

excess. .solulde in excess.

(ii.) A non-alkaline solution (ii.) It is not coagulated by

is coagulated by ether. ether.

6 PRACTICAL PHYSIOLOGY. [l.

EGG-ALBUMIN. SERUM-ALBUMIN.

(iii.) The precipitate with (iii.) The corresponding pre-

nitric acid is soluble with ditfi- cipitate is much more soluble

culty in excess of the acid. in excess of acid.

(iv.) The precipitate obtained (iv.) The corresponding pre-

by boiling is but slightly soluble cipitate is soluble in strong

in boiling nitric acid. nitric acid.

(v.) Its solution is not pre- (v.) Gives the same reactions

cipitated by j\rgS04, but is as in ( 5, I. /.).
completely precipitated by
(NH,),SO,.

[(vi.) When injected under [(vi.) When injected under

the skin, or introduced in large the skin, it does not appear in

quantities into the stomach or the urine.]
rectum, it is given off by the
urine.]

(3.) Lact-Albumin, see "Milk."

6. II. Globulins are insoluble in pure water, soluhle in (?ilufe
mline solutions — '\ri., NaCl, MgSO^, (NH^)oS04 — but insoluble in
concentrated or saturated solutions of neutral salts. Their solu-
tions in these salts are coagulated by heat. They are soluble in
dilute acids and alkalies, yielding acid- and alkali-albumin respec-
tively. Most of them are precipitated from their saline solution by
saturation with sodic chloride, magnesium sulphate, and some other
neutral salts.

(i.) Serum-Globulin. — It forms about haK of the total proteids
of blood-serum. It is insoluble in water, readily soluble in dilute
saline solutions (NaCl, MgS04). Its solutions give the general
reactions for proteids. Its NaCl solution coagulates at about
75° C.

(<7.) Neutralise 5 cc. of blood-serum with a few drops of dilute
sulphuric acid (o.i per cent.), then add 75 cc. of distilled water,
and allow the precipitate to settle. Pour off the fluid and divide
the precipitate into two portions, noting that it is insoluble in
water, but soluble in excess of acid.

(7^.) Boil a portion of the neutralised fluid = coagulation.

{<■.) Saturate blood-serum in a test-tube with magnesium sulphate,
shaking briskly for some time. Serum-globulin separates out and
floats on the surface. Filter, and test the filtrate for serum-
albumin.

{d.) Place 5 cc. of blood-serum in a tube, and pour a saturated
solution of magnesium sulphate down the side of the tube to form
a layer at the bottom of the tube. Where the two fluids meet
there is a white deposit of serum-globulin.

I.] THE PROTEIDS. 7

(e ) Saturate blood-soruni with crystals of sodium chloride or
neutral ammonium sulphate = separation of serum-globulin, Avhich
floats on the surface.

(/".) Precipitate the serum-globulin with magnesium sulphate,
and filter. To the filtrate add soilium sulphate in excess, which
gives a further precipitate. The filtrate may still give the reactions
for proteids.

(2.) Fibi-inogen, see " Blood."

(3.) Myosin, see " Muscle."

(4.) Vitellin. — Sliake the yolk of an egg with water and ether, as I'ng as
the washings show a j-ellow colour. Dissolve the residue in a minimal
amount of 10 ])er cent, sodium chloride solution. Pour it into a large quan-
tity of water, slightly acidulated with acetic acid = white precipitate of
impure vitellin.

{a. ) Di-ssolve some of the pr'ecipitate in a very weak saline solution, and
observe that it is not reprecipitated by saturation with sodic chloride.

(b.) Test some of the weak saline solution = coagulation about 75' C.

(c.) The precipitate is readily soluble in .1 per cent, hydrochloric acid, and
also in weak alkalies.

(5.) Crystallin is obtained from the crystalline lens.

(6.) Globin the proteid constituent of haemoglobin.

7. Ill, Derived Albumins (Albuminates) are compounds of
proteids with mineral substances. Those produced by the action
of acids or alkalies on albumins and globulins, yield respectively
acid-albumin and alkali-albumin. They are insoluble in pure water
and in solutions of sodium chloride, but readily soluble in dilute
hydrochloric acid and dilute alkahes. The solutions are not coagu-
lated by heat.

(i.) Alkali- Albumin or Alkali- Albuminate.

(a.) To dilute egg-albumin add a few drops of o.i per cent,
caustic soda, and keep it at 40° C. for 5-10 minutes = alkali-
albumin. Boil the fluid ; it does not coagulate.

(h.) Test the reaction ; it is alkaline to litmus paper.

(c.) Cool some of the alkali-albiuuin, colour it with litmus
solution, and neutralise carefully with o. i per cent, sulphuric acid = a
precipitate on neutrahsation, which is soluble in excess of the acid,
or of alkali.

(d.) Repeat (c.) ; but, before neutraUsing, add a feAv drops of
sodium phosphate solution (10 per cent.), and note tliat the
alkaline phosphates prevent the precipitation on neutralisation,
until at least sufficient acid is added to convert the basic phosphate
into acid phos]ihate. Tlie solution must lie decidedh' acid before a
precipitate is obtained.

(e.) Precipitate by saturating it with crystals of common salt or
magnesium sulphate.

(/.) Lieberkiilm's Jelly is a strong solution of alkali-albumin.

8 PRACTICAL PHYSIOLOGY. [l.

Place undiluted egg-white in a test-tube, and add strong caustic
potash. The whole mass becomes a jelly, so that the tube can be
inverted without the mass falling out.

(ff.) Its solution gives the general reactions for proteids under
1 (A.).

(2.) Acid- Albumin [or Syntonin].

Preparation. — (A.) To dilute egg-albumin, add o.i per cent, sul-
phuric acid, and warm gently for several minutes = acid-albumin.

(B.) To finely-minced muscle, r.g., of frog, add ten times its volume of
dilute hydrochloric acid (4 cc. of acid in i litre of water), and allow it to
stand for several hours taking care to stir it frequently ; filter, the filtrate
is a solution of a globulin combined with an acid, and has been called
syntonin.

(C.) Allow concentrated hydrochloric acid to act on fibrin for a time, and
filter.

(D.) It may be prepared by dissolving myosin in excess of . i per cent, HCl,
and after a time neutralising the solution with sodic carbonate.

(E.) To undiluted egg-white, add acetic acid = a jelly of acid-albumin.

Use the clear filtrate from (A.) or (E.) for testing.

(a.) The reaction is acid to litmus paper.

(/>.) Boil the solution ; it does not coagulate.

(r.) Add litmus solution, and neutralise with very dilute caustic
soda = a precipitate soluljle in excess of the alkali or acid.

{(l.) Repeat (c), but add sodium phosphate before neutralising ;
the acid-albumin is precipitated wiien the fluid is neutralised ;
so that sodium phospliate does not interfei'e with its precipita-
tion.

(e.) Add strong nitric acid = a precipitate which dissolves on
heating, producing an intense yellow colour.

(/".) It is precipitated like globulins by .saturation with neutral salts, e.g.,
NaCl, MgSO^, (NH,).,SO^.

{g.) Boiled with lime-water = i)artial coagulation.

8. IV. Caseinogen, tlie chief proteid of milk was formerly
regarded as a derived albumin. It is precipitated by acid. Like
globulins it is precipitated by saturating milk with NaCl or MgS04,
but it is not coagulat('(l Ijy lieat. (See " iMilk.")

9. V. Proteoses or Albumoses. — In the peptic and tryptic
digestion of pioteids these bodies are formed as intermediate pro-
ducts. In peptic digestion of allnunin, acid-albumin is first formed,
and finally peptone. Between tlie two is the group of proteoses or
alitumoses. Tliere are several of them, and they were formerly
grouped togctlier as hemi-albumose. These proteoses have been
subdivided into albumoses, globuloses, caseoses, &c., according as
they are derived from albumin, globulin, or casein. (See " Diges-
tion.") Witte's peptone usually contains a small amount of

I.] THE PROTEIDS. 9

peptone, and much albumose. Dissolve some of this body in warm
water, or preferal)ly in lo per cent, sodium chloride.

(a.) They are soluble in water ; not coagulated by heat ; and
are precipitated by saturation with neutral ammonium sulphate.
The precipitate with (XH^).,SO^ partly disajjpears on heating, and
reappears on cooling. They are precipitated but not coagulated
by alcohol.

(fj.) Add nitric acid = a white precipitate whicli dissolves with
heat (yellow thiid) and reappears on cooling. Run tap water on
the tube, the precipitate reappears. This is a characteristic re-
action, and occurs best in the presence of XaCl.

(c.) It, like peptone, gives a rosy-pivk with Piotrowski's test.

(d.) It is precipitated by acetic acid and ferrocyanide of potas-
sium, but the precipitate disappears on heating, and reappears on
cooUng.

(e.) It is precipitated by acetic acid and saturation with
XaCl. The precipitate di.sappears on heating, and reappears on
cooling.

10. VI. Peptones are hydrated proteids, and are usually produced
by the action of proteolytic ferments on proteids. They are exceed-
ingly soluble in water. Their solutions are not precipitated by
sodic chloride, acids, or alkalies, nor are they coagulated Ijy heat.
They are precipitated by tannic acid, and with difficulty by a large
excess of absolute alcohol. Xot precipitated by (>«'H^).3SC>^.

Preparation (see " Digestion "). — For applying the tests dissolve
a small cjuantity of Darby's fluid meat or commercial peptone in
warm water. Commercial pej-tone contains only a small amount
of peptone, and much alljumose.

(a.) Boil a portion ; it is not coagulated.

{h.) Xanthoproteic Reaction. — Add nitric acid, and boil = a
faint yellowish colour, and rarely any previous precipitate ; cool,
and add ammonia = orange colour.

(c.) Acidify strongly with acetic acid, and add ferrocyanide of
potassium = no precipitate.

{d.) Test separate portions with tannic acid ; potassio-mercuric
iodide ; mercuric chloride ; picric acid (saturated solution) ; and
lead acetate. Each of these causes a precipitate. Tu the case of
picric acid the precipitate disappears on heating, and reappears on
cooling.

{('.) Biuret Reaction. — Add excess of caustic soda, and then a
few drops of /•''/// dilnfr solution of copper sulphate = a roxe colour ;
on adding more coijjier sulphate, it changes to a violet.

(/.) Add a drop or two of Fehling's solution = a rose colour ; add
more Fehling's solution it changes to violet.

(//.) Neutrahse another portion = no precipitate.

lO PRACTICAL PHYSIOLOGY. [l.

(//.) Add excess of absolute alcohol = a precipitate of peptone,
but not in a coagulated form.

(?.) It is not precipitated by saturation with sodic chloride or
magnesic sulphate, nor by boiling with sodic sulphate and acetic
acid.

(./.) Pure peptone is not precipitated by saturation with neutral
sulphate of ammonia. N.B. — The other proteids are. Hence this
salt is a good reagent for separating other proteids, and thus leaving
the peptones in solution.

{k.) It also gives Millon's test.

(l.) Diffusibility of Peptones. —Place a solution of peptones in
a dialyser covered Avith an aninial membrane, as directed in Lesson
I. 1 (D.) ("?.), and t»st the diffusate after some time for peptones.
Peptones do not diffuse through a parchment tube.

(/».) Satiu-ato the solution of commercial peptones with (NH4)2
SOj = a precipitate of albumoses or proteoses. Filter. The filtrate
contains the piire peptone.

11. VII. Coagulated Proteids are insoluble in water, weak
acids, and alkalies, and are dissolved when digested at 35° to 40° C.
in gastric juice (acid medium), or pancreatic juice (alkaline
medium), forming first proteoses and finally peptones. They give
jNlillon's reaction.

Tliere are two subdivisions : —

(A.) Proteids coagulated by Heat.

Preparation. — Boil -white of egg hard, and chop up the white.

(a.) Test its insolubility in M-ater, weak acids, and alkalies.

(J}.) It is partially soluble in acids and alkalies, when boiled for
some time.

(c.) Bruise some of the solid boiled white of egg, diffuse it in
Avater, and test it Avith Millon's reagent.

('/.) For the effect of the digestive juices see "Digestion."

(B. ) Proteids coagulated by Ferment Action.

(i.) Fibr.'n is insoluble in water and in Aveak solutions of
common salt. When prepared from blood, and Avashed, it is a
Avhite, fibrous, soft, and very elastic substance, which exhibits
fibrillation under a high magnifying power (see " Blood ").

{a.) Place Avell-Avaslied fibrin in a test-tube, add o. i per cent,
hydrochloric acid. The fibrin sAvells up and becomes clear in the
cold, but does not dissolve.

{!>.) Repeat (a.), but keep on a Avater-bath at 60° C. for several
hours ; filter, and test the filtrate for acid-allnimin by neutralisation
with very dilute potash.

(c.) To a A^ery dilute solution of copper sulphate in a test-tube,
add fibrin. The latter becomes greenish, while the fluid is
decolourised. Add caustic soda, the flake becomes violet.

I.]

THE PROTEIDS.

II

{d.) For the effect of a dilute aeid and pepsin (see "Digestion"). These
"digest" fibrin, and convert it into proteose, and ultimately into peptone.

(«. ) It deeom])o.ses hydric ])eroxide, and turns freshly-prei)ared tincture of
guaiacum blue (see " Blood ").

(/. ) Digest fibrin in lo per cent, sodium chloride for two days. A small
part is dissolved ; boil the Huid = coagulation.

(ii. ) Myosin (see "Muscle"),
(iii.) Caskin (see "Milk"),
(iv. ) Gluten (see "Bread").

12. VIII. Lardacein, or Amyloid Substance. — This occurs in organs, e.g.,
liver and kidney, undergoing the ])atliological degeneration known as amyloid,
waxy or wax like, or albumenoid disease. It is insoluble in dilute acids or
alkalies, and it is not acted on by the gastric juice. It gives several distinct
reactions, not stains, with certain staining fluids.

(a.) A solution of iodine in iodide of potassium gives a deep brown or
mahogany stain when poured on a section of a fresh waxy organ.

(b.) With iodine and suljihuric acid occasionally a blue reaction is obtained.

(f.) Methyl-violet and gentian-violet give a rose pink reaction with the
wax}' parts, while others, i.e., the healthy jiarts of an organ, give diflerent
shades of blue or purple.

FlQ. 2. — Apparatus of Halliburton for Fractional Heat Coasulation of Proteids. T. Tap
for Water; C. Copper vessel with spiral tube; a. Iiilt-t, ami b. Outlet-tube to the
flask ; t. Test tube, with fluid anil thernioineter.

13. Fractional Heat Coagulation, p.ff., of blood-sfium. — The serum or
other Huid containing proteid is heated until a flocculent i)recipitate occurs.
Filter. The filtrate is again heated to a higher temperature, until a similar
])recipitate ajtpi ar.s. This precipitate is filtered off, and the above process
repeated, until the liquid is free of proteid.

The arrangements shown in fig. i may be used, but the rise of temjierature
takes jdace rather too slowly, and it is dilKcult to maintain the temperature
constant loi' a considerable length of time when one is investigating a large
number of fluids. The following apparatus used by Halliburton (fig. 2) is
more convenient. "A glass flask supjiorted on a stand ; down its neck is
])laced a test-tube, in which again is placed the liquid under investigation in
suflRcicTit quantity to cover the bulb of a thermometer ])laced in it. The flask
is kept filled with hot water, and this water is constantly flowing." It
enters by («), passing to the bottom of the flask, and leaves at {0). The

12 PRACTICAL PHYSIOLOGY. [l.

water is heated by passing through a coil o{ tubing contained in a copper
vessel, not unlike Fletcher's hot-water appai'atus. The fluid to be tested
must be well stirred by the thermometer during the progress of the experi-
ment.

In carrying out the experiment the following precautions are necessary,
viz., to keep the fluid under investigation as nearly as possible always of the
same reaction, as one of the important conditions influencing the temperature
of coagulation of a liquid is the amount of free acid present.

Use 2 per cent, acetic acid, and place it in a burette. It is dropped into
the fluid from the burette. The proportion is about one drop of this dilute acid
— after neutrality is reached— to 3 cc. of liquid. The acidity of the liquid is
tested by sensitive litmus papers. The liquid must be kept at a given
temperature for at least five minutes, to ensure complete precipitation of the
proteid at that temperature.

On heating certain solutions containing certain proteids, as the tempera-
ture of the fluid is raised, a faint opalescence appears first, and then, at a
higher temperature, masses or flocculi separate out, usually somewhat
suddenly, from the fluid.

The temperature at which coagulation of what is apparently one and the
same proteid occurs varies with a large number of conditions. Not only have
difl'erent proteids different coagulating points, which, however, can hardly in
the liglit of recent researches be called "specific coagulation temperatures,"
liut the coagulating temperature of any one proteid varies with the rapidity
with which coagulation takes place ; the proteid coagulates at a higher
temperature when the fluid is heated quickly than if it be heated slowly.
It also varies with the amount of dilution, the coagulating point being i-aised
by dilution. The effects of salts and acids in altering the coagulation point
are well known.

14. Kemoval of Proteids. — -The following, amongst otlier methods,
are used for removing proteids from li(|uids containing them. In
this way other substances present may l)e more easily detected.

IVenz's Method.- — Saturate with (NH4).2 SO4. This precipitates all proteids
except pe])tones.

Bii Ai'oiV ('/(I-/.— Acidulate faintly with acetic acid and boil. This removes
globulins and albumins.

Jiriirki'^s Mel hod. — Acidulate with HCl, and then add potassio-mercuric
iodide (see " Liver").

By A/cohol. — Acidify feebly with acetic acid, add several volumes of
absolute alcohol. After 24 hours all proteid is precipitated.

Gi7-gensohn''s Method. — Mix the solution with half its volume of a saturated
solution of sodium chloride, and add tannic acid in slight excess. This pre-
cipitates all proteids.

There are other methods in use.

n.] THE ALKUMENOIDS. 1 3

LESSON II.

THE ALBUMENOIDS.

The group of albumenoids inohiilcs a mimher of bodies Mdiich
in their general characters and elementary composition resemlile
proteids, but differ from them in many respects. They are amor-
phous. Some, of them contain sidphur, and others do not. Tlie
decomposition-products resemble the decomposition-products of
proteids.

1. I. Gelatin is obtained by the prolonged boiling of connective
tissues, e.i]., tendon, ligaments, bone, and from the sul:)stance
" Collagen," of which fibrous tissue is said to consist.

Preparation of a Solution. — jMake a watery solution (5 per
cent.) by allowing it to swell up in water, and then dissolving it
with the aid of heat.

(A.) (a.) It is insoluble, but swells up in about six times its
volume of cold water.

{h.) After a time heat the gelatin swollen up in water; it dis-
solves. Allow it to cool ; it gelatinises,

(B.) With General Proteid Tests.

(r.) Xanthoproteic Test. — Add nitric acid and boil = a light
yellow colour with no previous precipitate ; the fluid becomes
orange or rather lemon-coloured on adding ammonia.

{(1.) Millon's Reagent = no pinkish-red precipitate on boiling.
This shows the absence of the tyrosin group in the gelatin molecule.
Tliis reaction may be ol)tainecl with commercial gelatin, but not
with pure gelatin, so that the reaction if obtained is due to
impurities.

(e.) It gives a blue-violet, rather than a violet colour, with XaHO
and CuSO^.

if.) It is not precipitated by acetic acid and potassic ferrocj^anide
(unlike albumin).

{(J.) It is not coagulated by heat (unlike albumin).

(/(.) It is not coagulated by boiling with sodic sulphate and acetic
acid (unlike albumin).

(^■.) It is precipitated by saturation with ]\fgS04 or (XH^)2S04.

(C.) Special Reactions.

(./,) It is not precipitated by acids (acetic or hytlrochloric), or
alkalies, or lead acetate.

(/i-.) Add mercuric chloride = no precipitate (unlike albumoso and
peptone).

14 PRACTICAL PHYSIOLOGY. [ll.

(/.) Add tannic acid = copious white precipitate, insoluble in
excess.

(m.) Add picric acid (saturated solution) = yellowish-white pre-
cipitate, Avlucli disappears on heating and reappears on cooling.

(n.) It is precipitated by alcohol, and also by platinic chloride.

2. II. Chondi'in is obtained by the prolonged boiling of cartilage,
which largely consists of the substance " Chondrigen."

Preparation. — Costal cartilages freed of their perichondrium and cut into
small pieces are boiled for several hours in water, when an o])alescent fluid,
which gelatinises on cooling, is formed.

{a. ) Add acetic acid = a white precipitate, soluble in great excess.

(b.) Dilute mineral acids = white precipitate, readily soluble in excess.

(c.) It is not precipitated by acetic acid and potassic ferrocyanide.

3. III. Mucin, see " Saliva." It is also found in the ground
substance of connective tissue and tendon. There are probably
several mucins. On heating with dilute HgSO^ they yield a reduc-
ing sugar, and they are regarded as glucosides, compounds of a
proteid (globulin 1) with animal gum.

('/.) Tliey make fluids viscid and slimy.

(b.) Cut a tendon into pieces and place it for 3 days in lime-water. The
lime-water dissolves the mucin. Add acetic acid = ])recipitate of mucin.

4. IV. Elastin occurs in elastic tissue, ligamentum nuchse, and
ligamenta sul)flava, itc.

Pi;epai;ation'. — Boil the fresh ligamentum nuchiie of an ox successively in
alcohol, ether (to remove the fats), water (to remove the gelatin), and finally
in acids and alkalies. This substance must be previously piepared so that
the student can test its reactions.

(a.) It is insoluble in water, but is soluble in strong caustic soda.

(h.) It gives the xanthoproteic tests.

(c.) It is precipitated from a solution by tannic acid.

5. V. Keratin occurs in epitlielial structures, e.g., surface layers
of the epidermis, hairs, horn, hoof, and nails. It is characterised
by the large percentage of sulphur it contains ; part of the latter
is loosely combined. It is very insoluble and resists putrefaction
for a long time. A closely-allied body, Neuro-Keratin, is found in
nerve fibres and the central nervous system.

(a.) Burn a paring of horn, and note the characteristic smell,
(h.) Heat a paring of nail or horn with strong caustic soda and
lead acetate = black or brown colouration, due to lead sulphide.
(c.) Test for the presence of sulphur, (Lesson I. 2.)

III.] THE CARBOHYDRATES. 15

LESSON ITI.

THE CARBOHYDRATES.

The term Carbohydrate, fir.st used by C. Sclimidt, is applied to a
large and important group of substances, which occur especially in
plants, and some of which, such as starch and sugar, make up a
large part of their organs ; while cellulose, another member of the
group, forms the chief material from which many parts of plants
are constructed. Carbohydrates also occur, ])ut to a much smaller
extent, in animals, in which they are cliiefly represented by
glycogen and some forms of sugar.

In elementary composition they are non-nitrogenous, and consist
of C, H, and 0, with the H and 0 in the same proportion as in
water, i.^., 2 atoms of H to i atom of 0. As this proportion
obtains in many other substances which certainly do not belong
to the carbohydrate group, e.g., acetic acid (C2H4O.,), lactic acid
(0311^03), the definition must be somewhat extended. The group
is understood to include those substances that do not contain less
than 6 atoms of carbon, although many carbobydrates contain
multiples of this. To every 6 atoms of C there are at least 5
atoms of 0, so that on the one hand acetic acid is excluded, and
pyrogallic acid (Cj^HijOg) on the other.

They have certain general characters. They are indifferent
bodies, with a neutral reaction, which form only loose combina-
tions Avith otlier bodies, specially with bases. Other general
characters they possess directly, e.g., dextrose, or they can be
readily converted into bodies which have the following features in
common. One or other character may fail, but, as a group, they
have the following : —

(a.) The property of reducing alkaline metallic solutions, and of
being coloured yellow by alkahes.

{b.) They rotutt the ylaue of })olarised light.

(c.) In contact with yeast they split up into alcohol and carbon
dioxide, i.e., undergo fermentation. (Some do not undergo fer-
mentation.)

{(i.) On heating with HCl or H^SO^ they are decomposed \\'\W\
the formation of Idvulhiic acid, humin substance, and formic arid.

(e.) They give a deposit of yellow needles with phenyl-hydrazin.

(/.) Various cohmr rfoctions with acids and aromatic alcohols.

{g.) Some, e.g., cellulose and starch, are quite insalulile in water,
while others are very soluble. Those which are very insoluble in
water can usually be rendered soluble by heating them with an

\6

PRACTICAL PHYSIOLOGY.

[IIL

acid. Thi.s is a process of hydrolysis. They are less soluhle in
alcohol the more concentrated it is. In absolute alcohol (and
ether) almost all the carbohydrates are soluble with difficulty, or
insoluble.

{h ) "When strongly heated they are decomposed, charred, and
yield a variety of products. Inosite, which, however, is not a true
carbohydrate, alone undergoes partial sublimation (ToUem).

Classification of some Carbohydrates : —

I. Glucoses or
Monosaccharids,

C6H,P6.

n. Saccharoses or

Disaccharids,

C,,H.,,0„.

in. Amyloses or
Polysaccharids,

+ Dextrose.
- Ltevulose.
+ Galactose
Iuosite(?).

+ Cane-sugar.
+ Lactose.
-r Maltose.

-f Starch.
+ Dextrin.
-f Glycogen.

Cellulose.

Gums.

The -i- and - signs indicate that, as regards polarised light, the substances
are dextro- and Isevorotatory respectively.

The amyloses are anhydrides of the glucoses \j^{G^]^S>^ -
nW^O = (C,5Hj(,0.)„], while the saccharoses are condensed glucoses
(C,3Hi.30,; + C,jHi.,Og - H2O = Ci._,H,.,Oji)]. The saccharases are
converted into glucoses on boiling with dilute sulphuric acid.

^{c:S;a + h.o = 2c,h,o,

Emil Fi.scher has shown that the monosaccharids are aldehydes
or ketones of a hexatomic alcohol, C,;Hg (OH),;. Just as aldehyde
C.,H^O is formed by oxidising ethylic alcohol C.jH^O, so from
mannitic alcohol the simplest carbohydrate C,;HpOfi is formed.
"When two molecules of such monosaccharids polymerise with the
lo.ss of water, they form the disaccharids, which may split up
again and yield monosaccharids. "When there is further poly-
merisation with loss of water we get bodies with molecules of
larger size — the simpler members being dextrins, the more complex
starch and glycogen, forming the group of polysaccharids. These in
turn may break down and yield mono.saccharid or disaccbarid
molecules. Thus the transformation undergone by carbohydrates
in the organism, their conversion from one form to another, are
rendered more easy of comprehension.

in.]

THE CARBOHYDRATES.

T7

1. I. Starch (C^H^^jOr,),,. — The n in tliis case is not less tlian 4,
and may be 10 or 20; indeed, Brown and Heron snggest the for-
mula ioo(C,.,HoqOjq). ytarch is one of the most widely distri-
buted substances in plants, and it may occur in all the organs of
plants, either (a.) as a direct or indirect product of the assimila-
tion of CO^ in the leaves of the plant, or {!>.) as reserve material
in the roots, seeds, or shoots for the later periods of generation
or vegetation.

Preparation. — Wasli a potato tlioioughly, and grate it on a grater into
water in a tall cylindrical glass. Allow the suspended particles to subside,
and after a time note the deposit ; the lowest stratum consists of a white
powder or starch, and above it lie coarser fragments of cellulose and other
matters. Decant otl' the supernatant fluid which becomes brown on
standing.

(a.) Microscopical Examination. — Examine the wliite deposit
of starch, noting that each starch-granule shows an eccentric hilum

Fig.

-Potato Starch.

with concentric markings (fig. 3). Add a very dilute solution of
iodine. Each granule becomes blue, while the concentric markings
become more distinct.

{h.) Compare the microscopical characters of other varieties of starch — e.<i.,
rice, arrowroot, &c. Each granule consists of an outer layer of cellulose en-
closing alternating layers of granulose and cellulose, so that they present a
laminated aj)pearance. There are very great varieties in the shape and size
of starch giains.

(c.) Squeeze some dry starch powder between the thumb and forefinger, and
note the peculiar crepitation sound and feeling.

(rf. ) Polariscope. —Examine starch granules with a ])olarisation microscope.
With crossed Xicol's, when the field is dark, each granule sl.ows a dark cross
on a white refractive ground. They are doubly refractive. If a plate of mica
be placed on the stage of the microscope under the starch grains, the latter,
with polarised light, exhibit interference colours (fig. 4).

2, Prepare a Solution. — Place i gram of starch in a mortar,
rub it up with a little cold water, and then add 50 cc. of boiling
water. Eoil until an opalescent imperfect solution is obtained.

1 8 PRACTICAL PHirsiOLOGY, [ill.

(a.) Add powdered dry starch to cold water. It is insoluble.
Filter, and test the filtrate with iodine. It gives no blue colour.

(/'.) Boil starch with water = opalescent solution, which if strong
gelatinises or sets on cooling = starch paste.

(c.) Add a solution of iodine^ = a blue colour, which disappears
on heating (the iodi le of starch is dissociated by
heat) and reappears on cooling — provided it has not
been boiled too long. Direct a stream of cold water
upon the test-tube to cool it.

(fl.) Render some of the starch solution alkaline
by adding caustic soda solution. Add iodine solu-
tion. No blue colour is obtained.

(e.) Acidify ('/.) with dilute sulphuric acid, then

add iodine = blue colour is obtained.

Fig. 4. — Potato (/'.) To anotlier portion of the solution add a

uier'' view^in ^^^ drops of dilute cupric sulphate and caustic soda,

polarised light and boil = no reaction (compare " Grape-sugar ").

Nicoi's, 'x^^!' ('./■) To another portion of the solution add

Fehling's solution, and boil = no reaction.
(//.) Add tannic acid = yellowish precipitate, which dissolves on
heating.

3. Starch is a Colloid. — Place some strong starch solution in a
dialyser or parcliment tube, and the latter in distilled water.
Allow it to stand for some time, and test the water for starch ;
none Avill be found.

(a.) Does not filter. — Two dry filter papers are j)Iaced in two funnels about
5 cm. in diameter and filled with 2 per cent, solution of starch. Let one re-
main as a control, and to the other add any dia.static ferment — e.g., saliva
or liquor pancreaticus. The starch begins to filter, being converted into sugar.

4. II. Dextrin (British Gum) (CgHjoO^) is an intermediate pro-
duct in the hydration of starch. There are two varieties — Erythro-
dextrin, which gives a red colour with iodine ; and Ach-
roodextrin, Avhich gives no colour with iodine solution (see
" Saliva ").

Examine its naked eye characters. It is gummy and amor-
phous. Smell it. Dissolve some dextrin in boiling w^ater, and
observe that the solution is not opalescent.

(«.) This proves its solubility in water.

(b.) Add iodine solution = reddish-brown colour, Mdiich disap-
pears on heating and returns on cooling. [The student ought to
use two test-tubes, placing the dextrin solution in one, and an equal

1 Solution of Iodine. — Dissolve 2 grams of potassic iodide in 100 cc. of
water, add i gram of iodine, and shake well.

III.] THE CARBOHYDRATES. 1 9

volume of water in tlie other. Add to both an equal volume of
solution of iodine, and thus compare the difference in colour.]

(c.) Precipitate some of its solution by adding alcohol.

(rl.) Kender some of the dextrin solution alkaline by adding
caustic soda solution. No red-brown colour is obtained with
iodine. Acidify and the reddish-brown colour appears.

(e.) It is not precipitated by basic acetate of lead alone (unlike
glycogen).

(/'.) Precipitation occurs on adding ammonia and basic acetate of
lead. The ammonia gives a white precipitate "with lead acetate
which carries down dextrin.

There are several varieties of dextrin : —

5. Prepare Dextrin from Starch. — Make lo grams of starch into a paste
with 20 cc. of watpr. add ^o cc. of a 20 per cent, sohition of suli)liuric acid.
Mix, and lieat in a water-batli at 90' C. Cool and precijjitate tlie dextrin by
alcohol. Collect the white deposit, wash with alcohol, and dry it,

6. III. Cellulose (C,;H,„05)» occurs in every tissue of the liigher plants,
where it forms the walls of cells, and the great mass of the hard parts of
wood. Cotton-wool may he used to test its reactions.

(a.) It is insoluble in water and all the feebler solvents.

(b.) It is soluble in Schweitzer's reagent, or a solution of ammonio-cu])ric
oxide. This is prepared by dissolving slips of copper in ammonia in an open
flask, or by dissolving ])recipitated hydrated oxide of copper in 20 ])er cent,
ammonia. The former is prej)ared by precipitating a solution of sulphate of
coj)per by soda in tlie presence •of ammonium chloride.

(c.) It is soluble in concentrated acids, and a gelatinous precipitate — called
amyloid — falls on tlie addition of water. The sul)stance precipitated gives
a blue colour with iodine. It is also soluble in zinc chloride.

{'/.) It gives a blue colour with sulphuric acid and iodine, but not with the
latter alone.

7 IV. Glycogen or Animal Starch ?^(C^HjoO.,). — Prepare a
solution (see " Liver "). Xote the characters of the dry white
powder.

(a.) Note that the solution is opaleacmt (unlike dextrin); add
iodijie solution = red-brown or port-wine red colour. As in the
dextrin test, use two test-tubes, one with water and the other
with glycogen, to compare the dilference in colour. The colour
disappears on heating and reappears on cooling. It also dis-
appears on the addition of alkalies, which break up the feeble
compound.

{!).) Add caustic soda and coi)per sulphate solution = a blue
solution, boil = no reduction.

{c.) Add basic lead acetate = a i)rocii)itate (unlike dextrin).

('/.) Add ammonia and basic lead acetate = a precipitate, as in 1 /.

(''.) Boil with dilute hydrochloric acid = a reducing sugar.
Neutrahse the acid with dilute caustic soda, and test with Fehling's
solution for a reducing sugar, dextrose = a yellow precipitate.

20 PRACTICAL PHYSIOLOGY. [ill.

(/■.) The solution is precipitated by alcohol (2 parts absolute
alcohol to I part of the solution).

{(f. ) Heated with potash or acetic acid tlie opalescence diminishes, and the
soUition becomes clear.

{h.) Its solutions (even .6 per cent.) are powerfully dextro-rotatory

8. V. Glucose, Dextrose, or Grape-Sugar (C^Hj.,0,;).— In com-
merce it occurs in warty uncrystalliscJ masses of a yellowish or
yellowish-brown colour. It exists in fruits, and in small quantities
in the blood and other fluids and organs. It is the form of sugar
found in diabetic urine. It is readily soluble in water. Prepare a
solution by dissolving a small quantity in water.

(a.) Taste the glucose, and note
that it is not so sweet as cane-
sugar.

(A.) Add iodine solution = no
reaction.

{'-.) Heat the solution with sul-
phuric acid = darkens slowly.

(d.) Dissolve some in boiling
absolute alcohol. It crystallises in
transparent prisms when the alco-
hol cools (tig. 5).
As to the tests, they have been classified as follows : —

(A.) Yellow Colouration with Caustic Soda or Potash.

(.". ) Moore's Test. — Heat the solution with half its volume of caustic soda =
a yellow or brown colour due to the formation of glucic and melassic acids.
The non-appearance of a yellow colour indicates the absence ot dextrose, but
tlie following substances also give a yellow colour with NaHO : — All the
glucoses, together with milk-sugar and lactose.

(B.) Tests Depending on Reduction.

( /".) Trommer's Test. — To the solution add a few drops of a
dilute solution of cnjijier sulphate (10 per cent.), and afterwards
add caustic soda (or potash) in excess, i e., until the precipitate first
formed is re-dissolved, and a clear blue fluid is obtained. The
hydrated oxide of copper precipitated from the copper sulphate is
held in solution in presence of dextrose (and of all the glucoses).
Heat slowly, turning the tube in the flame. A little below the
boiling point, if grape-sugar be present the blue colour disappears,
and a yellow (cuprous liydrate) or red (cuprous oxide) precipitate is
obtained. Boil the upper surface of the fluid, and when the yellow
precipitate occurs it contrasts sharply with the deep blue-coloured
stratum below. The precipitate is first yellow, then yellowish-red.

Dextrose.

III.]

THE CARBOHYDRATES.

21

and finally red. It is Letter seen in reflected than transmitted
light. If no sngar be present, only a black colour may be
obtained.

(//.) Add Fehling's solution ; boil = a yellow or yellowish-red
precipitate of cuprous oxide or hydrate. [For the method of
making Fehling's solution, the precautioiis to be observed in using
it, and for some other tests for glucose, see " Urine."]

(/(..) Barfoed's Sohition. — To 200 cc. of a sohition of neutral acetate of
cojijier, containing i part of the salt to 15 of water, add 5 cc. of a 38 per cent,
.solution of acetic acid. When heated witli dextrose some red cuprous oxide
is precipitated, while lactose, cane-sugar, maltose, and dextrin, when they
are boiled with it for a short time, give no reaction. Hence tins substance
has been used to distinguish dextrose from maltose.

(/. ) Bbttger's Bismuth Test. — Heat the fluid with caustic soda and a small
quantity of dry basic bismuth nitrate = a grey or black reduction ])roduet of
bismuth oxide. For Xylander's modification, see " Urine." In all reactions
dejiending on reduction, one must recollect that some substances wliich are
by no means related to the glucoses — e.g., uric acid, kreatinin, phenyl-
liydrazine — may cause reduction, and thus lead one into error.

(C.) other Reactions.

(./.) Phenyl-Hydrazine Test. — Two parts of plienyl-hydrazine
hydrochloride and three of acetate of soda are mixed in a test-tube
with 6-10 cc. of the dextrose
solution. Boil for 20-30
minutes, and then place the
tube in cold water. If sugar
be present, a yellow crystaUine
deposit is formed, wliich,
microscopically, consists of
yellow needles either detached
or arranged in rosettes (tig.
6). The substance formed is
phenyl-glucosazone
(CjgHo^N^O^), with a melting-
point of 204° C.

The arrangement of tlie
acicular crystals I find fre
quently varies. Sometimes
they are in rosettes (see " Urine "), and
feathery. They are soluble in alcohol, and may be recrystallised
from it.

This is an extremely important and reliable reaction. The best
proportions for the ingredients are i part dextrose, 2 hydrochloride
of phenyl-hydrazine, 3 sodic acetate, and 20 water. The substance

Fig. 6.— Crystals

i>f Plienyl-Gliiciisazone, x izo.

at other times more

I Blue with iodine.

22 PRACTICAL PHYSIOLOGy. [ill.

formed is but slightly soluble in water. According to E. Fischer,
the following is the reaction which takes place : —

C,Hi,0, + 2C,H5N2H3 = Ci8H2.3N,0, + 2H,0 + 2H.

Phenj-l-glucosazone.

(l:) Molisch's Test. — (i.) To the .solution add a drop or two of a 15-20 ])er
cent, alcoholic solution of a-naphthol, and 1-2 vols, of concentrated sulphuric
acid. The colour which first appears is violet ; water causes a hluisli-violet
deposit, (ii. ) If instead of the najjhthol, an alcoholic solution of thymol be
used, a red colour is obtained. Seegen, however, points out that this re-
action can be obtained with other substances, e.g., albumin, which, however,
is denied by Molisch. It is not a reliable test.

9. Conversion of Starch into Glucose. — Boil starch solution
with a few drops of 20 per cent, sulphuric acid, until the fluid
becomes clear. After neutrahsing with sodium carbonate, test tho.
duid for glucose by the tests (h.) or (c).

A large number of intermediate products, however, are formed.
They are as follows (see also " Saliva ") : —

Starch .

Soluble starch (amidulin or amylodextrin)

^^^P ^^^ I Erythrodextrin .... Iodine gives violet and red.

pj .. • j Achroodextrin ..... No reaction with iodine.

,, ,, I Fehling's solution reduced.

^I^^tose I Barfoed's not.

Dextrose Both are reduced.

Estimation of Glucose (see " Urine ").

10. VI. Maltose (CjgH.^.jOjj). — It forms a fine white warty
mass of needles, and is the chief sugar formed by the action of
diastatic ferments on starch. See "Saliva," and "Pancreatic
Juice."

(a.) Mix I gram of ground malt with ten times its volume of
water, and keep it at 60° C. for half an hour. Boil and filter ; the
filtrate contains maltose and dextrin.

(h.) Test for a reducing sugar with Fehling's solution or other
suitable test. (See also " Salivary digestion.")

(r.) Boiled for ih hours with the phenyl-hydrazine test it yields
phenyl-maltosazone (Co^HggN^Oy). It cry.stallises in yellow
needles (fig. 8).

(1^.) It is solu1)le in water and alcohol. Examine its crystals
(fig. 7). Its .specific rotatory power is + 150°, i.e., it is greater
than tliat of dextrose, but its reducing power (on Fehling's solution)
is only two-thirds of that of dextrose.

(r.) With Barfoed's reagent, i.e., when boiled with half its volume of copper
acetate, acidulated with acetic acid = no reduction. In this respect, and in
some others, it differs from dextrose.

III.]

THE CARBOHYDRATES.

23

(/.) Preparation of Maltose. — Take i part of potato-starch and make it
into a jiaste with 10 of water. Digest the paste with a filtered extract of
low-dried malt (200 grams to i litre of water) for an hour at 57-60^ C, filter,
evaporate, {)recii)itate the dextrin with alcohol, concentrate the filtrate to a
syrup, and allow the maltose to crystallise.

11. Estimation of Maltose.^(i.) Determine its reducing power
on 10 cc of Feliling's solution (see " Urine").

(ii.) Convert it into dextrose by boiling (i- an hour) 50 cc. of the
solution with i cc. of H^SO^. Cool and bring the solution to the
original volume (50 cc.) by adding water. Again determine its
reducing power by Fehling's solution If a: = cc. of maltose
solution necessary to reduce 10 cc. of Fehling's solution, then as

Fig. 7. — Crystals of Maltose.

Fig. 8.— Crystals of Phenyl- Maltosazone, x 120.

the respective reducing powers of glucose and maltose are as 2 : 3

2X

— = cc. of dextrose solution necessary for the same purpose. As

10 cc. of Fehling correspond to o 05 grms. dextrose, the strength
of the maltose solution can easily be calculated.

12. VII. Lactose (Milk-Sugar), C,,H.,,Oii + H,0 (see " Milk ").

(a.) Note its Avhitencss and hardness. It is not so sweet as
cane-sugar. Microscopically it occurs in rhombic prisms (fig. 9).

(/>.) it is less soluble in water than cane- or grape-sugar, and
insoluble in alcohol.

{(•.) Heat its solution carefully with sulphuric acid = chars
slowly.

{(i.) Add excess of caustic soda, and a few drops of copper
sulphate solution, and heat = yellow or red precipitate (like
dextrose).

{e.) Test with Fehling's .solution = reduction like dextrose, but its
reducing power is not so great as dextrose. It requires 10 parts of
lactose to reduce the amount of Fehling's solution that will be re-
duced by 7 of dextrose.

24

PRACTICAL PHYSIOLOGY.

[III.

(f.) It is precipitated from its saturated watery solution by
absolute alcohol.

Fig. 9.— Crystals of Lactose.

Fig. to. — Crystals of Plienyl-iactosazone, x 12c

{(/.) The phenyldiydrazine test (fig. 10), it yields phenyl-lactosa
zone (C^^HgaN^Og).

13. Preparation of Lactose (C|., H.,jO I, +H..0). — Acidulate milk with acetic
acid = precipitate of caseinogen and fat ; filter; boil filtrate to precipitate albumin,
and filter again ; eva])orate the filtrate to small bulk ; set aside to crystallise.

Milk-sugar is soluble in 6 parts of cold and 2^ parts of hot water, but not in
alcohol.

14. VIII. Cane-Siigar (G.^U.^^O^-,).

(a.) Observe its crystalline form
(fig. 11) and sweet taste.

(/>.) Its solutions do not reduce
Feliling's solution (many of the
commercial sugars, however, con-
tain suiiicient reducing sugar to do
this).

('•.) Trommer's test : add excess
of caustic soda, and a drop of solu-
tion of copper sulphate (it gives a
clear blue fluid), and heat. "With
a pure sugar there should be no reduction.

(d.) Pour strong sulphuric acid on cane-sugar in a beaker, add
a few drops of water ; the whole mass is quickly charred.
(e.) Heat the solution with caustic soda = it darkens slowly.
(/.) It is practically in.^oluble in absolute alcohol, but its solu-
bility greatly increases with the dilution of the alcohol.

{(/.) Inversion of Cane-Sugar. — Boil a strong solution of cane-
sugar in a flask with one-tenth of its volume of strong hydro-
chloric acid. After prolonged boiling the cane-sugar is "inverted,"

Fig. II.— Crystals of Cane-sugar.

11 r] THE CARBOHYDRATES. 2$

ami the solution contains a mixture of dextrose and Isevulose.
Test its reducing power with Fehling's solution.

Cani'-Siigar. Waler. (ilucose. L.'cvulose.

C,,H,,0,^ + H,0 = C,dl,,(), + C.H^A-

(h.) Estimation of Cane- Sugar.— Take lo cc. of the cane-sugar
solution, add i cc. of a 25 per cent, solution of If.,SO^. Boil for
half an hour, and tiii-n make up bulk of Huid to its original
V'>Uime. The cane-sugar is converted into a reducing sugar,
dextrose. Place the fluid in a burette, and estimate its reducing
power on FehUng's solution (see " Urine.") 95 parts of glucose
correspond to 100 parts of cane-sugar.

15. Invert Sugar — a lui.vture of graj.e-sugar and fruit-sugar -is widely
distriluitod throughout the vegetahle kingdom, and is so called because it
rotates the plane of polarised light to the left, the specific rotatory power of
the laevulose being greater than that of dextrose at ordinary temperatures.

16. Conversion of Starch into a Eeducing Sugar. — Place 50
cc. of starch solution in a flask on wire gauze over a Bunsen burner,
add one drop of strong sulphuric acid, and boil from five to ten
minutes, observing the spluttering that occurs, the liquid meantime
becoming clear and limpid.

(a.) Test a portion of the liquid for glucose, taking care that
sufficient alkali is added to neutralise the surplus acid.

(/'.) Add iodine = blue colour, showing that some soluble starch
(amiduhn) remains unconverted into a reducing sugar.

ADDITIONAL EXERCISES.
Polarimetere.

17. Circumpolarisat'on.— Certain substances when dissolved po.ssess the
power of rotating the i)lane of polarised light, r.g., the proteids, sugars, kc.
The extent of the rotation depends on the amount of the active substance
in solution. Tlio direction of rotation — i.e., to the right or the left - is
constant for cacli active substance. Of course, light of the same wave-
length must be used. The light obtained from the volatilisation of common
gelt is used.

The term ''specific rotatory power," or "specific rotation" of a substance,
is used to indicate the amount of rotation expressed in degrees of the ])lane of
polarised light which is ])roduced by i gram of the substance dissolved in
I cc. of liquid, wlien examined in a layer i decimetre thick.

Those substances which cause specific rotation are spoken of as " optically
active ;" those wliich do not, as '' wactive,"

26

PRACTICAL PHYSIOLOGY.

[III.

If a = the observed rotation ;

J) = the weight in grams of the active substance contained in i cc. of

liquid ;
^ = the length of the tube in decimetres ;
(a)D = the specific rotation for light corresponding to the light of a
sodium flame ;
then

The sign + or -indicates that the substance is dextro- or laevo-rotatory.
Various instruments are employed. Use

Laurent's Polarimeter. — This instrument is a so-called " half-shadow
polarimeter," and must be used in a dark room (fig. 12).

Fig 12. — Laurent's Half-Shadow Polarimeter.

18. Determination of the Specific Rotatory Power of Dextrose.

(a.) Fill one of the decimetre tubes with distilled water, taking care that

III.]

THE CARBOHYDRATES.

27

no air-bubbles get in. Slip on the glass disc horizontally, and screw the
brass cap on the tube, taking care not to do so too tightly. Place the tube
in the instrument, so tliat it lies in the course of the rays of polarised light.

(6.) Place some common salt (or fused common salt and soda carbonate) in
the platinum spoon (A), and light the Bunsen's lamp, so that the soda is
volatilised. If a platinum spoon is not available, tie several platinum wires
together, dip them into slightly moistened common salt, and fix them in
a suitable holder, so that the salt is volatilised in tiie outer part of the Hanie.
In the newer form of the instrument supplied by Laurent, there are two
Bunsen-burners, placed the one behind the other, wliich give very much
more light. Every part of the apparatus must be scrupulously clean.

FiG. i-i. — Wild's Polaristroboineter.

(c.) Bring the zero of the vernier to coincide witli that of the scale. On
looking through the eye-piece (0), and focussing the vertical line dividing
the field vertically into two halves, the two halves of the field should have
the same intensity when the scale reads zero. If this is not the case, then
adjust the prisms until it is so. by means of the milled head placed for that
purpose behind the index dial and above tlie telescope tube. It is well to
work with the field not too brightly illuminated.

(d.) Remove the water-tube, and substitute for it a similar tube containing
the solution of the substance to be examined — in this case a p''rfecth/ dear
so/utiim of pure dextrose. Place the tube in position, and proceed as before.
The two halves of the field are now of unequal intensity. Rotate the eye-
piece until equality is obtained.

('■. ) Repeat the proce.ss several times, and take the mean of the readings.
The diti'erence between this reading and the first at (<•.), when the tube

28

PRACTICAL PHYSIOLOGY.

[in.

was filled with distilled water — i.e., zero = is the rotation due to the
dextrose = a.

(/.) Place lo cc. of the solution of dextrose in a weighed capsule, evaporate
to dryness over a water-bath, let the capsule cool in a desiccator, and weigh
again. The increase in weight gives the amount of dextrose in locc. ; so that
the amount in i cc. is got at once = 7).

{g. ) Calculate the specific rotatory power by the above formula. It is about

+ 53°.

For practice, begin with a solution of dextrose containing 1 1 grams per loo cc.
of water. Make several readings of the amount of rotation, and take the mean.

Example. — In this case, the mean of the readings was ii.6\

(«)d =

11.6°

= 53

Repeat the process with a 4 and 2 per cent, solution. It is necessary to be
able to read to two minutes, but considerable practice is required to enable one
to detect when the two halves of the field have exactly the same intensity.

Test the rotatory power of corresponding solutions of cane-sugar, and any
other sugar you please.

Test also the rotatory power of a proteid solution.

The following indicate the S.R. for yellow light : -

Proteids.— Egg-albumin - 35.5° ; serum-albumin - 56° ; syntonin
— 72°; alkali-an3umin prepared from serum-albumin - 86^, when
prepared from egg-albumin - 47'.

Carbohydrates. — Glucose + 56° ; maltose -f 1 50° ; lactose -i- 52.5'.

N.B. — A complication sometimes arises in connection with carbohydrates,
as the S.R. is sometimes much altered by the temperature ; thus the S.R. of
Iffivulose, when heated from 20-90° C, falls in the pro-
portion of 3 : 2. It is best, therefore, to work at a
constant temperature, say 20' C. Again, some solutions
have not the same S.R. when they are first dis.-olved
that they have twenty-four hours afterwards. This is
called birotation, and it is therefore well to use the
solution twenty-four hours after it is made.

Wild's Polari trobometer. — Between tbe
polariser (wliicb can be rotated) and analj'ser
of tbis instrument is placed a Savart's polari-
scope, "wbicli produces in the field a number of
parallel dark interference-lines.

A framework H, which can be moved on a brass
support F, carries the analyser and polariser. The
light from a soda-f!ame enters at D, traverses a Nicol's
prism which is fixed to and moves with the graduated
index K. The ])o]arised rays then traverse the fluid
contained in a tube placed in L, and reach the fixed
ocular parts containing the so-called polariscope. The
latter is composed of two prisms, which give rise to the interference-lines, which
are viewed by means of a lens of short focus. Between M and N is a diaphragm
with X -shaped cross lines. Beyond M, which is designed to protect the eye

Fig. 14. — a. Interference-
lines seen with tig. 13.

IV.] THE CARBOHYDRATES. 29

of the observer from extraneous light, is the other Nicol's prism. The
polariser can be rotated by means of C. In order to read oil' the scale, there
is a telescope B. In S is a small mirror which reflects the tlame of a
movable source of light upon the nonius. Usually the instrument is made
for a column of lluid 220 mm. long.

(i.) Light the movable gas-Harae opposite Q. Estimate the zero-point of
the instrument by placing an empty tube in the instrument, and focus until
the lines of the cross are sharply seen. Rotate the polariser by means of C
until the illuminated field is seen to be traversed by dark interference-lines
(fig. 14, «). On rotating still further, the lines become paler, until ultimately
a clear space without lines occupies the field. Try to get this in the middle
of the field as in fig. 14, h.

(2.) Replace the empty tube with the fluid to be investigated, when the
interference-lines reappear. Suppose the substance is dextro-rotatory, then
rotate the Xicol to the left until the lines disappear ; but from the arrange-
ment of the apparatus, the milled-head C is moved in the same direction as
the direction of rotation of the substance. It is well to make readings in all
four quadrants of the instrument. It is best to use the instrument in a dark
room.

LESSON IV.

FATS— BONE— EXERCISES ON THE FOREGOING.

NEUTRAL FATS.

The neutral fats of the adipose tissue of the body generally con-
sist of a mi.xture of the neutral fats stearin, palmitin, and olein,
the former two being solid at ordinary temperatures, while olein
is fluid, and keeps the other two in solution at the temperature
of the body.

Neutral fats are derivatives of the triatomic alcohol glycerin,

H3 r

3»

and are glycerides or compound ethers of palmitin, stearin, and
olein, in which three of the hydrogen atoms of the glycerin are
replaced by as many equivalents of the acid radical.

I. Reactions.

{n.) Tliey are ligliti-r than water; sp. gr. .91-.94.

(/>.) Use almond or olive oil or lard, and observe that fat is
soluble in ether, chloroform, and hot alcohol, but iiisoliMe in
water.

(c ^ Dissolve a little fat in 3 cc. etlier. Let a drop of the

30

PRACTICAL PHYSIOLOGY.

[IV.

ethereal solution fall on paper, e.g., a cigarette paper = a greasy
stain on the paper, which does not disappear with strong heat.

{d.) To olive oil or suet add caustic potash, and boil. Stearin is
present in the suet and is glycerin-stearate, while olein in olive
oil is glycerin-oleate. When stearin is boiled with a caustic
alkali, e.g., potash, a potassic stearate or soap is formed, and
glycerin is set free. This is the process of saponification.

Tri-Steaiin.

3CisH,,0 )

C3HJ

Potash.

0, +

K
3h

Potas.sic Stearate (Soap), Glycerin.
0 = 3^-"-k}^:^ + ^h'}^3

[e.) Heat lard and caustic soda solution in a capsule to form a soap; decom-
]>ose the latter by heating it with dilute sulphuric acid, and observe the
liberated fatty acids floating on the top.

(/". ) Proceed as in ('/.), and add to the soap sohition crystals of sodium
chloride until the soaps separate.

{g.) Shake oil containing a fatty acid, e.g., De Jongh's cod-liver
oil, with a few drops of a dilute solution of sodic carbonate. The
whole mass becomes white = emulsion. Examine it microscopi-
cally, and compare it with milk, which is a typical emulsion.

In an emulsion the particles of the oil are broken up into
innumerable finer particles, which remain discrete, i.e., do not run
together again.

ill.) Shake up olive oil Avith a solution of albumin in a test-
tube = an emulsion. Examine it microscopically.

(/.) Gad's Emulsion Experiment. — Place in a watch-glass a solution of
sodic carbonate (.35 per cent.), and on the latter place a droj) of rancid oil.

The drop comes to rest, but soon the oil
drop shows a white rim, and at the same
time a white milky opacity extends over
the soda solution. With the microscope,
note the lively movement in the neighbour-
hood of the fat-droplet, due to the separa-
tion of excessively minute particles of oil.
The white fluid is a fine and uniform
emulsion (fig. 15). This experiment has
an important beaiing on the formation of
an emulsion in the intestine in connection
with the pancreatic digestion of fats.

(/. ) Eanvier's Emulsion Experiment. —
Ranvier has shown that if a drop of lymph
taken from the peritoneal cavity of a frog
be mixed on a micro.scopical slide with a
drop of olive oil, on examining with a
microscope where the two fluids come into
contact, one sees emulsification going on before one's eyes, with the forma-
tion of fine particles of oil like the molecular basis of chyle {Comptes reiidas,
1894).

Fig. 15.— Gad's Experiment.

IV.] FATS — BONE. 3 I

{k.) Heat in a porcelain capsule for an hour or more some lard mixed with
plumbic oxide and a little water. The fat is split up, yielding glycerin and
a lead-soap.

BONE.

2. (A.) Organic Basis of Bone.

(a.) Decalcify Bone. — Place a small thin dry bone in dilute
liydrochloric acid (i : 8) for a few days. Its mineral matter is
dissolved out, and the bone, although retaining its original form,
loses its rigidity, and becomes pliable, and so soft as to be capable
of being cut with a knife. What remains is the organic matrix or
ossein. Keep the solution oljtained.

(''. ) Wash the decalcified bone thorouglily with water, in which it is in-
soluble ; place it in a solution of sodium carbonate and wash again. Boil it
in water, and from it gelatin will be obtained. Neutralise with sodium
carbonate. The solution gelatinises. Test the solution for gelatin (Lesson
II. 1).

(f.) Decalcify a small portion of a dry bone with picric acid.

(B.) Mineral Matter in Bone.

(a.) Examine a piece of bone wliich has been incinerated in a
clear fire. At first the bone becomes black from tlie carbon of its
organic matter, but ultimately it becomes white. What remains
is calcined bone, having the form of the original bone, but now it
is quite brittle. Powder some of the white bone-ash.

(b.) Dissolve a little of the powdered bone-ash in hydrochloric
acid, observing that bubbles of gas (CO.,) are given off, indicating
the presence of a carbonate ; dilute the solution, add excess of
ammonia = a white precipitate of phosphate of lime and phosphate
of magnesia.

('".) Filter, and to the filtrate add ammonium oxalate = a white
precipitate of oxalate of lime, showing that there is lime present,
but not as a phosphate.

('/.) To the solution of mineral matters 2 (A.) (a.) add acetate
of soda until there is free acetic acid present, recognised by the
smell ; then add ammonium oxalate = a copious white precipitate
of lime salts.

(c.) Use solution of mineral matters obtained in 2 (A.) (a.) Render a j)art
alkaline with NH,HO = copious jtrecipitate, redissolve this in acetic acid,
which dissolves all except a small llocculent residue of phosphate of iron
(perhajts in part derived from the blood of bone). Filter ; use a small part to
test for phosphoric acid and the rest for calcium and magnesium (Filtrate A.).

(i. ) The undissolved Hocculent precipitate is waslied and dissolved in a tew
cc. dilute HCl. and the presence ot iruii oxuie proved by adding ferrocyanide of
potassium (= blue), and that o{ phosiihoric acid by molybdate of ammonium
(see " Urine"),

32 PRACTICAI. PHYSIOLOGY. [iV.

(ii.) With the filtrate A. test for pliosphoric acid by uranium acetate =
yellowish -white precipitate of uranium pliosjjhate (UrO,)HP04.

(iii.) Cnhium, by adding ammonium oxalate Ca^CjG^ + H.jO. Filter, and
when the filtrate is clear and gives no longer a precipitate with ammonium
oxalate, make it alkaline with NHjHO^ after a time crystalline precipitate of
ammonio - magnesium phosphate MgNH;P04 + 6H20, showing presence of
tiiagnesmm.

3. EXAMINATION" OF A SOLUTION FOE, PROTEIDS
AND CARBOHYDRATES.

I. Physical Characters.

(a.) Note colour and transparency. Glycogen solution is
opalescent, starch and some proteid solutions less so.

{}>.) Taste. Salt solution may contain glolKilin. A sweet taste
indicates a sugar.

(c.) Smell. The beef-tea odour of albumose and peptone solution,
and the smell of British gum are characteristic.

{d.) Other characters. Thus a persistent froth is suggestive of
an albuminous solution.

II. Test for proteids by xanthoproteic and Millon's tests. If
present :

1. Test reaction to htmus paper. If acid or alkaline, test for
acid- or alkali-albumin, and if either is present, neutralise, and
filter off precipitate. Test filtrate for proteoses and peptones as in
4 and 5.

2. If original solution is neutral, acidulate famtly, and boil. A
coagulum may consist of native albumin, or globulin, or both. Filter;
and test filtrate for proteoses and peptones as in 4 and 5.

3. Distinguish between albumin and glolnilin by {a.) dropping
solution into water, precipitate indicates globulin, {h.) saturating
solution with jNIgSO^, precipitate ■-= globulin, Init may also contain
proto- and hetero-albumose. If precipitate obtained by {h), filter
and boil filtrate, coagulum = native-albumin. Distinguish between
egg- and serum-albumin by ether test.

4. Add excess of NaHO, then, drop by drop, very dilute CuSO^,
pink colour indicates proteoses, or peptones, or both.

5. Separate proteoses from peptones by saturating solution "with
Am^SO^. Precipitate = proteoses. Filter ; and to filtrate add larye

v.] THE BLOOD. 33

excess of syrupy solution of NaHO, then dilute CuSO^. Pink
colour indicates peptones.

[6. Gelatin (albuminoid), gives Xanthoproteic and Millon's re-
actions, gives a violet colour with NallO and CuSO^, is not coagu-
lated by boiling, and is not precipitated by acetic acid and potas-
sium ferrocyanide.]

III. Test for Carbohydrates. First remove derived albumins
by neutralising and filtering, and native albumin and globulin by
boiling and filtering.

1. Acidulate if necessary and add iodine.

(a.) Blue coloiir, disappearing on heating and returning on cool-
ing, indicates starch.

(/>.) MahcMjany-broion colour, disappearing on heating and return-
ing on cooling, indicates glycogen or dextrin. Add basic lead
acetate, precipitate (if proteids are absent) = glycogen.

2. Test for reducing sugar by Trommer's test. If present, dis-
tinguish glucose, maltose, and lactose, by the phenyl-hydrazine test

(p. 2l).

3. If no starch, dextrin, glycogen or reducing sugar, examine for
cane-sugar by inversion test.

LESSON V.
THE BLOOD— COAGULATION— ITS PROTEIDS.

1. Reaction, — Constrict the base of one finger by means of a
handkerchief. When the finger is congested, with a clean sewing
needle prick the skin at the root of the nail. Touch the blood
with a strip of dry, smooth, neutral litmus paper, highly (/lazed to
prevent the red corpuscles from penetrating into the test paper.
Allow the blood to remain on it for a short time ; then wash it off
with a stream of distilled water, when a blue spot upon a red or
violet ground will be seen, indicating its aUmline reaction, due
chiefly to sodium phosphate (Xa.JIPO^) and sodium carbonate.

2. Blood is Opaque.

(r/.) Place a thin layer of defibrinated blood on a glass slide ; try
to read printed matter through it. This cannot be done.

3. To make Blood Transparent or Laky. — Place 10 cc. of de-
fi1)rinated blood in each of tliree test-tubes, labelled A, B, and C.
A is for comparison.

(a.) To B add 5 volumes of water, and warm slightly, noting
the change of colour by reflected and transmitted light. By re-

o

34 PRACTICAL PHYSIOLOGY. [V.

fleeted light, it is much darker, it looks almost black — hut by
transmitted light it is transparent. Test this by looking as in 2
(a.) at printed matter.

(b.) To C add a watery solution of taurocholate of soda. Test
the' transparency of the mixture. In 2, the hasmoglobin is still
Avithin the blood corpuscles. In the others — 3 (a.), (b.) — it is
dissolved out, and in solution.

4. Specific Gravity of Blood. —(rt.) Make a number of solutions of sulphate
of soda, varying in sp. gr. from i. 050-1. 075. At least twenty separate solu-
tions are required, each with a definite sj). gr. Pour a small quantity of the
solutions into small glass thimbles. A thin glass tube is drawn out in a gas-
flame to form a capillary tube, which is bent at a right angle, and closed
above with a small caoutcliouc cap. A drop of blood is obtained from a
finger, and by pressing lightly on the caoutchouc cap a quantity of the
fi'eshly-slied blood is drawn up into the capillary part of the tube. The tip of
the fine capillary tube is at once immersed in one of the solutions of sodic sul-
phate, and a droj) of the blood expressed into the saline solution, and it is noted
whether it sinks or Hoats. The operation is repeated with other solutions until
one is found in which the blood neither sinks nor floats. The sp. gr. of blood
varies from 1045-1075, the average sp. gr. being 1056-1059.

(h.) Haycraft's Method.— Make a mixture of toluol (s. g. 800) and benzyl
chloride (s. g. iioo) to obtain a fluid with a s. g. of 1070. Label this A.
Make another with the s. g. 1025. Label this B.

Method. — With a j)i{)ette jilace a measured quantity of A in a warm cylin-
drical glass. Aild a drop of the blood. It will float ; now add B until the
blood neither floats nor sinks.

Suppose 1.5 cc. of B has been added to i cc. of A, then

I cc. of A (1070)= 1,070
1.5. 1,5 cc. of B (1025)= 1,537

2.5 cc. 2,607

Divide this by the total volume 2.5 cc. = 1043, the s. g. of the blood.

5. Action of a Saline Solution.

(a.) To 2 cc. of defibrinated blood in a test-tube (D) add 5
volumes of a i o per cent, solution of sodium chloride. It changes to
a very bright, florid, brick-red colour. Compare its colour with that
in A, B, and C. It is opaque.

6. Red Corpuscles. — Add to defibrinated ox blood (or, better, dog's blood),
20 voliunes of a dilute solution of NaCl f.5-2 per cent.). The red corpuscles
subside, and tlie su])ernatant fluid can be jwured ofl". Wash the corpuscles
several times in tiiis way. They will be required for the preparation of
ha-moglobin (jt. 65).

7. Haemoglobin does not Dialyse.

(a.) Place a watery solution of defibrinated blood in a dialyser
(a bulb form or a parchment tid^e), and suspend it in a large
vessel of distilled water. Test the dialyser beforehand to see

v.]

THE BLOOD. 35

that there are no holes in it. If there are any fine pores, close
them with a little white of egg, and coagulate it with a hot iron.

(/>.) After sev(;ral hours observe that no hseraoglobin has
passed into the water.

(r.) Test the dilfusate for clilorides (AgXOg + HNO3).

8. Phenomena of Coagulation. — Decapitate a rat, and allow
the blood to flow into a small porcelain capsule. Within a few
minutes the blood congeals, and when the vessel is tilted the blood
no longer moves as a fluid, but as a solid. It then coagulates com-
pletely. Allow it to stand, and after an hour or so, pale-yellow
coloured drops of fluid — the serum— are seen on the surface, being
squeezed out of the red mass, the latter being the clot, which con-
sists of fibrin and the corpuscles.

9. Formation of Clot and Serum. — Draw out a glass tube into a fine
capillary pipette at both ends, leaving a bulb in the middle, and suck some
uncoagulated blood, either from one's finger, or from the lieart of a frog, into
it, seal up tlie ends of the tube, allow the blood to coagulate, and e.xamine
the tulje under a microscope. Observe the small red shrunken clot, and the
serum squeezed out of the latter.

10. Frog's Blood - Coagulation of the Plasma. — Place 5 cc. of normal
saline (0.75 per cent, salt solution) in a test-tube surrounded witli ice.
Expose the heart of a pithed frog, and oj)en the ventricle, allowing the blood
as it escapes to flow into the normal saline. Mix, and the corpuscles (owing
to their greater sj)ecific gravity) after a time subside. After they have
subsided remove the supernatant fluid — the plasma mixed with normal
saline — by means of a pipette. Place it in a watch-glass, and observe that it
coagulates.

11. Mammalian Blood.

(A.) Study coagulated Idood obtained from the slaughter-house.
Collect the blood of a sheep or ox in a perfectly dry cylindrical
vessel, and allow it to coagidate. Set it aside for two days, and
then observe the serum and the clot. Pour off the pale, straw-
coloured serum, and note the red clot, which has the shape of the
vessel, although it is smaller than the latter.

(B. ) If the blood of a horse can be olitained, study it, noting that the upper
layer of the clot is paler in colour ; this is the buffy coat.

12. Circiimstances Influencing Coagulation.

Effect of Cold. — Place a small jilatinum capsule — a brass or glass thimble
will do quite well— on a freezing mixture of ice and salt, decapitate a frog or
rat, and allow the blood to flow directly into the cooled vessel. At once it
becomes solid or congeals, but it is not coagulated. As soon as the blood
becomes solid, remove the thimble and thaw the blood by jilacing it on the
palm of the hand, when the blood becomes fluid, so that it can be ]>oured into
a watch-glass ; if the vessel be once more jilaced on the freezing mixture, the
blood again congeals and solidifies, and on its being removed becomes fluid.
Observe at the same time that the colour and transparency of the blood are

36 PRACTICAL PHYSIOLOGY. [V.

altered. The blood becomes darker in colour and transparent. This is the
laky condition due to the discharge of the hreraoglobin from the corpuscles.
Place the vessel with the fluid blood on the table, and it clots or forms a firm

jelly.

13. Salted Plasma— Influence of Neutral Salts on Coagu-
lation. — At the slauglitcr-house, allow blood to run into an equal
volume of saturated solution of sodium sulphate (or one quarter
of its volume of a saturated solution of magnesium sulphate) ;
mix. The hlood does not clot, but remains fluid. Place the
vessel aside on ice, and note tliat the corpuscles subside, leaving
a narrow clear yellowish layer on the surface — tlie plasma mixed
with the saline solution, and known as salted plasma. To obtain
sufficient plasma, the blood must be " centrifugalised " (page 43),
to separate the corpuscles from the plasma.

(a.) Heat undiluted salted plasma to 60° C. The fibrinogen is
precipitated at 56° C. Filter. The filtrate will not coagulate,
even after the addition of fibrin-ferment and CaCl.,, as there is no
fibrinogen present.

{h.) Place 1 5 ce. of the salted plasma in a tall, narrow, cylindrical,
stoppered glass tube. Add crystals of sodium chloride, and shake
the whole vigorously, when a white flocculent precipitate is thrown
down. Allow the precipitate to subside. ])ecant tlie supernatant
fluid. Filter through a filter moistened with a saturated solution
of sodic chloride, and wash the precipitate on the filter with a
saturated solution of sodic chloride. This is the plasmine of Denis.
With a spatula, scrape the washed precipitate off the filter.

Dissolve the plasmine in a small quantity of distilled water,
and filter quickly. The filtrate, if set aside, will clot after a
time. It is better to do the several operations rapidly to ensure
success, but I have frequently found coagulation occur when the
plasmine Avas not dissoh-ed in water until many hours after it was
deposited.

14. Oxalate Plasma. —Oxalate of potassium prevents blood from
coagulating when present to the extent of 0.2 per cent. Dissolve
I gram of potassium oxalate in 10-20 cc. of normal sahne, place
it in a vessel capable of holding 500 cc, and allow blood to run
in to fill the vessel. Mix the two fluids, 'i'lie 1)lood does not
coagulate, but remains fluid. Ceiitrifugalise it to obtain the
oxalate plasma, which may be siphoned off. The oxalate pre-
cipitates— as oxalate of lime- the calcium which is necessary for
coagulation.

(a.) To oxalate plasma, add a few drops of a 2 i)er cent,
calcium chloride solution = coagulation, and more quickly at
40° C.

v.] THE BLOOD. 37

15. Defibiinated Blood. — In a slaughtor-house allow the blood
from an anim;il to run into a vessel, and with a bundle of twigs
beat or whip the blood steadily for some time. Fine white fibres
of fibrin collect on the twigs, while the blood remains fluid. This
is defibrinated blood, which does not coagulate spontaneously.

16. Fibrin. — "Wash away tlie colouring-matter with a stream of
water from the twigs until the fibrin becomes quite white.

(a.) Physical properties : it is a Avhite, fibrous, elastic substance.
Stretch some fibres to observe their extensibility ; on freeing them,
tliey regain their shape, siiowing their elasticity.

(b.) Place a few fibres in absolute alcohol to rob them of water. Tlie}-
become brittle and lose their elastlcit}\

{c.) Place a small quantity of fibrin in a test-tube with some
0.2 per cent, hydrochloric acid in the cold. It swells up and
becomes clear and transparent, but does not dissolve.

{d.) Repeat (/.), but place the test-tube in a water-bath at 6o' C. ; part of
the fibrin is dissolved, forming acid-albumin. Test for the latter (Lesson I. 7).

{p.) Place some hydric peroxide over fibrin in a watch-glass ;
bubbles of oxygen are given oft'. Immerse a flake in freshly-
prepared tincture of guaiacum (5 per cent, solution of the pure resin
in alcohol), and then in hydric peroxide, when a blue colour is
tleveloped, due to the ozone liberated by the fibrin striking a blue
with the resin. If the fibrin contains much water, it is preferable
to place it first of all for a short time in rectified spirit to remove
the water. [Other substances give a blue colour under similar
conditions ]

(/.) Place some fibrin in water in a test-tube. Xote that it gives the
xanthoproteic reaction and Millon's test (Lesson I. 1).

('/.) Prick a finger with a needle, collect a drop of blood on a microscopic
slide, cover, and examine under a microscope ( x 350). After a time, observe
the tbrmation of threads of fibrin between the rouleaux of coloured blood-
cor})Uscles.

17. II. Blood-Serum. — By means of a pipette remove the serum
from the coagvdated blood or siphon it oft" (Lesson V. 8). If a
centrifugal apparatus is available, any suspended blood-corpuscles
can easily be separated by it. Xote its straw-yellow colour anil
musky odour. Its reaction alkaline. Its sp. gr. = 1034.

General Proteid Reactions.

(a.) Dilute i volume of serum with 10 volumes of normal saline
or salt solution.

(/>.) Test separate portions by neutrahsation and heat = coagu-
lation ; nitric acid and the subsequent addition of ammonia ; acetic

38 PRACTICAL PHYSIOLOGY. [V.

acid and ferrocyanide of potassium ; Millon's reagent ; and the
NaHO and Cu!SO^ reaction (Lesson I. 1). Alcohol causes coagu-
lation.

('•.) Saturate it with anunonium sulphate. This precipitates all
the proteids, glohulin and allmrnin. Filter , the filtrate is proteid-
free.

Study its individual proteids.

(A.) Preparation of Serum-Globulin (Paragloljulin).

(a.) A. Schmidt's Method. — To lo cc. of serum add 200 cc. of ice-cold
water, and pass a stream of carbon dioxide through it for some time = a white
precipitate of serum-globulin. This method does not precipitate it entirely.
No precij)itate is obtained unless the serum be diluted.

(h.) Panum's Method. — Dilute 1 cc. of .serum with 15 cc. of water; add 5
drops of a 2 per cent, solution of acetic acid-=a white precipitate of serum-
globulin, or, as it was called, " serum -casein." All the serum-globulin is not
precipitated.

(c.) Hammarsten's Method. — Saturate serum with magnesium
sulphate, and shake briskly for some time. An abundant precipi-
tate of serum-globuhn is obtained. Allow the excess of the salt
and the precipitate to settle. The undissolved crystals fall to the
bottom, and on their surface is precipitated a dense white flocculent
mass of serum-globulin. Filter. Wash the precipitate on the
filter with a saturated solution of magnesium suliDliate , add a little
distilled water to the precipitate. It is dissolved, ?>., it is a globulin,
and is insohible in excess of a neutral salt, but is dissolved by a
weak solution of the same. The solution does not coagulate spon-
taneously. It gives all the reactions for proteids with tlie special
reactions of a gloljulin.

('/.) Kauders Method. — Add to serum half its volume of a
saturated solution of ammonium sulphate (i.e., half saturate it) =
precipitate of the globulin. Complete saturation precipitates the
albumin as well.

Only methods (c) and (d) are now used. Kauder's method enables
one rapidly to separate the gloljulin and then the albumin by the
use of one salt.

(e.) Allow a few drops of serum to fall into a large quantity of
water, and observe the milky precipitate due to the presence of a
globulin = serum-glo!)ulin. This is best observed by placing a dead
black surface behind the vessel of water. We can then trace the
" milky way " of the falling drops of serum as they traverse the
water.

(B.) Serum- Albumin.— From (A.), (c), filter oft' the precipitate,
and test tbo filtrate for the usual proteid reactions. It is evident
that the filtrate still contains a proteid, which is serum-albumin
(Lesson I. 5, 2). To the filtrate add sodic sulphate, when serum-

v.] THE BLOOD. 39

albumin is precipitated, fsodic sulpliate alone, however, gives no
precipitate with pure serum.

18. Precipitation of Serum Proteids by Other Salts.

(rt. ) Precipitate blood-serum with jiotassic phosphate. All the proteids arc
thrown down after prolonged shaking.

(b.) Precipitate blood-serum with magnesic sulphate and .sodic sulphate, or
the double salt sodio-magnesic sulphate. All the proteids are thrown down.

19. Coagulation Temperature of Serum-Proteids. — Saturate

serum witli MgSU^. Pilter, keep the filtrate, lahi'I it 11 Wash
the precipitate, i.e., the serum-globulin with saturated solution of
magnesium sidphate until tlie washings give no reaction for albu-
min. This takes a long time, and had better be done previously
by the demonstrator. Dissolve the precipitate in distilled water,
Avhich gives an opalescent sohition. Label it A. Acidify it
slightly with a drop of 2 per cent, acetic acid, and determine the tem-
perature at which it coagulates by the method stated on p. 11.
The litjuid in the test-tube should just cover the bulb of the
thermometer. Coagulation takes place about 75' C.

The filtrate B contains the serum-albumin. Dilute it with an
equal volume of water, faintly acidify and heat, as above. A pre-
cipitate falls about 77-79° C. (B), and on filtering this ofi", and
again acidifying, another precipitate is obtained on heating to
84-86° C.

20. Preparation of Fibrinogen from Hydrocele Fluid, which
does not coagulate spontaneousl3^

(a.) Dihite lo cc. of hydrocele fluid with 150 to 200 cc. of water, and pass
through it for a considerable time a stream of carbon dioxide, when there is
precipitated a small quantity of a somewhat slimy white body, fibrinogen.
(Schmidt's method.)

(b.) Half saturate hydrocele fluid with sodium chloride solution
bv adding to it an equal volume of .saturated sohition of .sodium
chloride. Fibrinogen is precipitated in small amount. Filter, and
on adding ^IgS^j, serum-globulin is precipitated, so that hydrocele
fluid contains both fibrinogen and serum-globulin.

21. Coagulation Experiments.

(a.) Andrew Buchanan's Experiment. — Mix 5 cc. fresh seriun
(preferably from horse's blood) with 5 <zc,. hydi'ocele fluid and
keep the mixture at 35° C. for some hours, when coaciulation occurs,
a clear pelhuid clot of fibrin being obtained. Coagulation takes
place, and is due to the action of fibrin-ferment on fibrinogen and
not to the presence of serum-globulin, as hydrocele fluid in addition
to fibrinogen contains this body.

40

PRACTICAL PHYSIOLOGY.

[V.

(/>.) To 5 cc. of hydrocele fluid add some solution of fibrin-
ferment, and keep in a water-bath at 40° C. coagulation takes
place.

(/■.) To 2 cc. of salted plasma, prepared as in Lesson Y. 13
(which is known to clot slowly on the addition of water), add lo
volumes, ?>., 20 cc. of a watery sohition of fibrin-feim^nt, pre-
pared by the demonstrator = coagulation.

(d.) Add to oxalate-plasma (Lesson Y. 14) a few drops of a 2
per cent, calcium i:hloride solution. It coagulates, and more quickly
at 40° C. The CaCl., supplies the calcium necessary for the forma-
tion of fibrin.

(e.) Effect of Temperature on Coagulation. — Dilute sodium
sulphate plasma with 10 volumes of water, and place some in test-
tubes A, B. C, D.

A clots slowly or not at all.
Place B in water-bath at 40°
C. It clots more quickly.

To C add a small quantity
of fibrin-fermont (p. 40), dis
solved in a little calcium
chloride.

To I) add serum. Keep C
and D at 40° C. They coaj/u-
lated rapidly, because of the
abimdance of fibrin-ferment.

22. Preparation of Fibrin-Fer-
ment.— It must be kej)t in stock.
KiG. i6.-E\iiMntnv for Dr.viii- a Precipitate Precinitjte blood-serum with a large

over Sulpliunc Acid. 0. ljla«s bell-iar, cover- • i i„ i i n ,i j.v,„ „„.,;„,,„

ing vessel with sulphuric acid (c), and support excess of alcohol, collect the copious
(d) for the deposit or precipitate. precipitate, consisting of the pro-

teids and fibrin-ferment. Cover it
with absolute alcohol, and allow it to stand at least a month, when the pro-
teids are rendered insoluble. Dry the precipitate at 35° C, and afterwards
over suljihuric acid (fig. 16). Keep it as a dry ])Owder in a well-stoppered
bottle. When a solution is required, extract some of the dry powder with 100
volumes of water ; filter. The filtrate contains the ferment.

23. Salts and Sugar of Serum. — The usual salts may be tested
for directly with serum diluted with water^ or the following method
may be adopted : —

Dilute blood and boil it ; filter.

Colourless filtrate, which can be tested
for salts and sugar.

Coagulum coloured brown by hae-
matin.

v.l

THE BLOOt). 41

The blood is heated with 6 to 8 times its volume of water, and sliglitly
acidulated. The filtrate is evaporated to a small bulk. When a drop of the
concentrated filtrate is placed on a slide, cubes of common salt separate out.

To the colourless filtrate of 23

(a.) Add silver nitrate = white curdy precipitate soluble in
ammonia, but insoluble in nitric acid = chloride'^.

(/>.) Add barium chloride = white, heavy precipitate insoluljle in
nitric acid = snlpliaies.

{('.) Add nitric acid and molybdate of ammonium and heat =
yellow precipitate =]>Iiosi)liate^.

{'!.) Test with Fehhuf^'s solution or CuS(\ and XaHO and boil
= red cuprous oxide = reducing siujar, which is glucose.

ADDITTOXAL EXERCISES.

24. To Obtain Clear Serum. —The best way to obtain this is by means cf a
centrifugal apparatus : but il the serum contain blood -corpuscles, a fairly
clear fluid may be obtjiined by placing it in a vessel like
(fig. 17). It consists of the separated top ot a wide flask
provided with a cork in the neck, and in the cork is an
adjustable tube provided with a clip. When the serum
is ])laced in the apparatus, it must be above the level
of the tube. On opening the clip, tlie clear serum can be
drawn oil without distuibiug the deposit.

25. Preparation of Serum - Albumin and Serum-

Globidin.- Dilute clear serum with three volumes of a ^^?- '^^ur.ut}'^,''^^^^

. 114. 1 f'^f Obtauniijj Clear

saturated solution ot neutral ammonium sulphate, and Scrum.

add crystals of the same salt to complete saturation.
Filter. The deposit contains tlie two above-mentioned substances, and is
washed with a saturated solution of (NH4)^S0j. The deposit is tlien dis-
solved in the smallest possible amount of water and dialysed in a p;u'chnient
tube. Ill proportion as the salt dialyses. tiic serum-globulin is deposited as a
white powder in the dialysiiig tube, whilst the serum-albumin remains in
solution. It is not difficult to ilevise an apj)aratus whereby the water is
kept flowing, and even the dialysis tuhe kept in motion in the running water,
provided one has some motor power at haiul. (S. Lea, Journal of Fhysiology ,
xi. p. 226).

After complete dialysis the fluiil is filtered, tlie deposited serum globulin is
collected and washed. The filtrate— which contains tlie serum-alluimin — is
carefully neutralised with iimmonia, again dialysed, filtered and concentrated
at 40" C. After it is cold, the serum-albumin is precipitated at once by strong
alcohol, expressed, washed with ether and alcohol, and dried.

PRACTICAL PHVSIOLOGY.

[V.

Serum-albumin is completely precipitated from its solution by ammonium
sulphate, but not at all by magnesic sulpliate. A solution, free from senim-
globulin, containing 1-1.5 per cent, of salts, coagulates at about 50 , with 5
per cent, of XaCl at 75'-8o' C.

26 Estimation of Grape-Sugar in Blood.— (a.) Place 20 grams of crystal-
lised sodic sulphate in each of three porcehiin capsules, and to eucn add exactly
20 grams of the blood to be investigated. Mix the blood and salt together
Boil them until the froth af.ove the clot becomes white, and the clot itsell
does not present any red specks. Weigh again, and make up the loss by
evaporation by the addition ot water. Ihewliole is
then placed in a small press, and the fluid part ex-
pressed, collected in a capsule, and afterwards filtered.
The filtrate is placed in a burette.

In a flask ]}lace I cc. of Fehling's solution, and to it
add a few .-mall pieces of caustic potash and 20 cc. of
distilled water. Boil this fluid, and from the burette
allow the clear filtrate of the blood to droj) into the
boiling dilute Fehling's solution until the latter loses
everv trace of its blue colour (fig. iS). As in all sugar
estiiimtions, the process must be repeated several times
to get accurate results. Hence the reason why several
capsules are prepared.

Read oW, on the burette, the number of cc. of the
filtrate used, e.g.=n cc. The formula

n
in grams the weight of sugar per kilogram of blood.
{Bi'riKird.)

(b.) In Seegen's Method, which may be taken as
the type of the newer methods, the proteids are pre-
cipitated by ferric acetate. The blood is diluted with
8-10 times its volume of water, acidulated with acetic
acid, and heated. When the precipitation of proteids
commences, render the mixture strongly acid by the
addition of acetate of soda and perchloride of iron ;

_ __^ then add sufiicient sodic carbonate until the mixture

~ is faintly acid, and boil. Allow it to cool, and filter

FIG. rS.-Bernard's Appa- ^^ through a fine cloth filter, free from starch. The

ratiis for KstimaUn^' the '" /^' & ,., . , „ia.j,. TI.p vp«iV1iip on the

Sugar in Wood. filtrate ought to be cleai. iUe le&iriue on tiie

filter is washed several times with water, and the

remaining fluid in it expressed by means of a small hand-press. The expressed

fluid is then mixed with tiie clear filtrate. If the mixture has a slight reddish

tint from the admixture of a small quiuitity o.^ bloo.i-pigment. Add a droj.

or two of perchloride of iron to precipitete the last traces ot the protei.Js.

Filter again. The sugar in the filtra,te is estimated in the usual way by

means of 1 ehling's solution.

27 Ash of Hsemoglobin.- Incinerate a small quantity of oxy-hamoglobin
in a platinum capsule. Tliis is done in the manner shown in fig. 19, where
theca])sule is placed oblifjuelv, and its contents heated m a Bunsen-flame
until only the ash remains, the ash is red, and consists of oxide 01 iron.

(a.) Dissolve a little in hydrochloric acid ; add jiotassic sulphocyanide = a
red precipitate, + ferrocyanide of potassium = a blue precipitate.

VI.]

THE COLOURED BLOOD CORPUSCLES.

45

28. The Centrifugal Machine. — Precijtitates or very luinule j.articles
suspended in a fluid, e.g., blood-
corpuscles in seruni may be readily
separated by this aj)j)aratus.

The liquid is placed in strong glass
tubes, and these are in turn placed
in metallic cases, which can move on
a horizontal axis, the cases themselves
being placed in a horizontal disc
which is driven at the rate of looo
revolutions per minute ; this causes
the tubes to take a horizontal posi-
tion, and after 30-40-60 minutes
rotation the precipitate or other sus-
pended particles are found at the
outer end of the tube. The serum
can thus be obtained perfectly
corpuscleless.

There are various forms of this
apparatus. Some can be driven by
the hand and yield small quantities
of fluid, such as those sold by
Muencke of Berlin (see Stirling's
Outliaes of Pradkul Histolog)/, p. 94,
2 Ed. 1893) or that made by Watson pj^
& Laidlaw of Glasgow. When large
quantities of fluid are required, that
made by Fr. Runne of Basel is one of the best. It requires a water or
gas-motor to drive it. At the i)resent time Runne's " Werkstatte f. prac.
Mechanik " are situated in Heidelberg.

-Method of Incinerating
Obtain the Ash.

a Deposit to

LESSON VI.

THE COLOURED BLOOD CORPUSCLES.

SPECTRA OF H.EMOGLOBIX AXD ITS COMPOUNDS.

Enumeration of the Corpuscles,— Several forms of instruments
are in use, e.7., those of Malassez, Zeiss, Bizzozero. and Gowers.

1. Tlie Haemocytonieter of Gowers (fig. 20) can be used Avith
any microscope, and consi.sts of —

(a.) A small pipette, which, when fillec to tlie mark on its stem,
holds 995 o.mm. (fig, 20, A).

(h.) A capillary tube to hold 5 c.mm, (B).

(c.) A small glass jar in wliich the blood is diluted (D).

(d.) A glass stirring rod (E),

(e.) Fixed to a brass plate a cell V of a millimetre deep, and with

44

PRACTICAL PHYSIOLOGY.

[VI.

its floor divided into squares -,V mm., in which the blood-corpuscles

^"""(rrThe'dihiting solution consists of a solution of sodic sulphate
in distilled water— sp. gr. 1025.

2 Mode of Using the Instrument.

(a.) By moans of the pipette (A) place 995 cmm. of the dilut-
ing solution in the mixing jar (D). u. ^f

(b ) Puncture a finger near the root of the nail with the lancet
projecting from (F), and with the pipette (B^ suck up 5 cmm. of

1 t„- A -Piripffp fnr mpasuriii'' tlie diluting solutiim ; B.
^-/:^!;=;S^^ffit'c4K^r^5>e ^. a suae, ..

the Wood, and blow it into the diluting sohition, and mix the two
with the stirrer (E). , ■,,

(. ) Place a drop of the mixture on the centre of the glass cell
(C , see that it exactly fills the cell, and cover it gently with he
cover-glass, securing the latter with the two springs 1 lace he
cell with its plate on the stage of a microscope, and focus for the
so uares ruled on its base. .

(d) AVhen the corpuscles have subsided, count the number in
ten squares, and this, when multiplied by 10,000, gives the number
in a cubic millimetre of blood.

VI.]

THE COLOURED BLOOD CORPUSCLES.

45

(e ) Wash the in.struraeiit, and in cleanmg the ocll do tliis with
a stream of distilled water from a wash-bottle. Take care not to
brush the cell with anything rougher than a camel's-hair pencil, to
avoid injuring the lines.

Each square has an area of y^ of a square mm., so that lo
squares have an area of yV of a square mm. As the cell is i mm.
deep, the volume of blood in lo .squares is tV^t= sV c.mm. On
counting the number of corpuscles in lo squares, and multiplying
by 50, tins will give the number in i c.mrn of the diluteil blood.
C)n multiplying this by i-^^"-^, we get the number in i c.mm. before
dilution. Thus we arrive at the reason why we multiply the
number in 10 squares by 10.000 to get the number of corpuscles in
I cram, of blood.

/\

^

HAEMOGLOBIN AND ITS DERIVATIVES.

3. Preparation of Hsemoglobin Crystals, (C.jooHgg^N^s^Oi^jjSFe).

(a.) Rat's Blood.— Place a drop of detibrinated rat's blood on a
slide, add three or four drops of water,
mix, and cover with a cover-glass. Ex-
amine with a microscope ; after a few
minutes small crystals of oxy-h;emo-
globin will begin to form, especially
at the edges of the preparation, and
gradually grow larger in the form of
thin rliombic plates arranged singly or
in groups (tig. 21).

{/>.) Guinea-Pig's Blood.— Treat the
blood of a giunea-pig as directed for
the blood of a rat. Tetrahedral crystals
are obtained. Mount some defibrinated
blood in Canada balsam. Crystals
form.

Fig. 21.— Hscnioglobiii Crystals
(f. ) Dog's Blood. — To 1 5 cc. of aenl)nnatea from Pwat's Blood,

dog's blood add, drop by drop, i cc. or

so of ether, shaking tlie tube after e^ch addition of ether. By this means
the blood is rendered Inki/, a condition which is recognised by inclining
the tube, and observing that the film of blood left on it, on bringing the
tube to the vertical again, is transparent. Add no more ether, but plaoe the
tube in a freezing mixture of ice and salt ; as the temperature falls, crystals
of haamoglobin separate. If the crystals do not separate at once, keep the
tube in the freezing mi.xture for one or two days. Examine the crystals
microscopically. Arthus finds that dog's blood, containing i per cent, of
sodic fluoride, after standing for several days, according to the surrounding
temperature, deposits crystals of lib.

^ZZ^

46

PRACTICAL PHYSIOLOGY.

[VI.

4. Ozone Test for Haemoglobin.— Mix some freshly-prepared
alcoholic solution of guaiacum with ozonic ether ; the mixture
becomes turbid, and on adding even a dilute sokition of hemo-
globin, a blue colour results, due to oxidation of the resin by the
ozone liberated from the ozonic ether by the haemoglobin.

5. Spectroscopic Examination of Blood.

ing's straight- vision spectroscope (fig. 22).

-Use a small Brown-

FiG. 22— Browning's Straight- Vision Spectroscope.

Preliminary.— Observe the solar spectrum by placing the
spectroscope before the eye, and directing it to bright daylight.
Note the spectrum from the red to the violet end, witli the inter-
mediate colours, and focus particularly the dark Fraunhofer's hnes,

known as J) in the yelloAv, E in
the green, h, and F, their position
and relation to the colours. jMake
a diagram of the colours, and the
dark lines, indicating the latter by
their appropriate letters.

('I.) Fix the spectroscope in a
suitable holder, and direct it to a
gas-flame, the edge of the flame
being towards the slit in the spec-
troscope, noting that the spectrum
shows no dark Fraunhofer lines.

(h.) Fuse a piece of platinum
wire in a glass tube, and make a
loop at the free end of the wire
(fig. 23). Dip the platinum wire
in Avater and then in common
salt, and burn the salt in tlie gas-
flame, having previously directed the spectroscope towards tlie gas-
flamo, and so arranged the latter that it is seen edge-on. Note the
position of tlie bright yellow sodium line in the position of the
line D,

F:g. 23. — Stand for Platinum Wire for
Sodium Flame.

vr.]

THE COLOURED BLOOD CORPUSCLES.

47

6. I. Spectrum of Oxy-haemoglobin.

(a.) Bfgin with a slioiig solution and gradually dilute it. Place
some deliljrinated blood in a test-tube, and observe its opacity tuid
bright scarlet colour.

(h.) Adjust the spectroscope as follows : — Light a fan-tailed ga.'*-
burner, fix the spectroscope in a suitable holder, and between the
light and the sht of the spectroscope place a test-tube containing
the blood or its solution. Focus the /o«^ i7Hage of the gas-flame on
the slit of the spectroscope. The focal point can be readily ascer-
tained by holding a sheet of white paper behind the test-tube.

Yellow.

Green.

nine.

B C 0 E b

4o 50 bo 70 80

.l,,,.lMul.M.lnMl,,,.|.M,liinlHnlMi '

Kio. 24.— Spectra of Ha;mo(ilobin, and its Cumiiounds. 1. Oxy-lua-iiKiglobin. o3 iht rent.;
2 Oxy-lijemoglobin, 0.18 per cent.; 3. Carbonic oxide liiBnioglolnn ; 4. I!educe<l luemo-
globin.

(c.) Add 10 to 15 volumes of water, and note that only the red
part of the spectrum is visible. Make a sketch of what you see,
noting the dilution

('/.) Add more wator until the green appears, and observe that
a single dark absorption -ban 1 appears between the red and green
(fig. 24, i). Continue to dilute until this .single broad band is
resolved into two by the transmission of yellow-green light. Burn
a bead of sodic chloride in the gas-flame, to note distinctly the
position of the 1) line, and observe that of the two absorption
bands the one nearest D, conveniently designated by the letter a,
is more sharply deflned and narrower; while the other, cou-

48

PRACTICAL PHYSIOLOGY.

[VI.

veniently designated by the letter /8, nearer the violet end, is
broader and fainter. At the violet end the spectrum is shortened
by absorption (fig. 24, 2).

(1?.) Continue to dilute the solution, and note that the band near
the violet end is the first to disappear.

Usmg coloured chalks or pencils, sketch the appearances seen with
each dilution, and indicate ojiposite each the degree of the latter.

{/.) A very instructive method is to make a pretty strong solu-
tion of blood, showing only one undivided band. Place a httle
of this in a test-tube, and pour in water, so that the water mixes
but shghtly with the upper strata of the blood. Examine the
solution spectroscopically, moving the tube so as to examine first

FlO. 25. — Oraiihic Representati )n of the
Absorption of Light in a Spi ctruni
by Solutions of Reduced Hb, of dif-
ferent strengths. The shading indi-
cates the amount of absorption of the
spectrum, and the numbers at the
side the strength of the solution.

aCB

Fig. 26. — Graphic Representation of the
Absorption < f Li^lit in a Spectru" by
Solutions of O.\y-hieinoglobiii, of differ-
ent strengths. The shading indicates
the amount of alisorption of tlie spec-
trum, and the numbers at the side the
strength of the solution.

the deeper strata of fluid until the surface is reached. At first
a single band is seen ; but as the solution is more dihite above,
tlie two bands begin to appear, and as the solution gets weaker above,
the ^-band disajjpears, until, finally, with a very weak solution,
such as is obtained in the upper strata only, the a-band alone is
visible.

Fig 26 .shows the amount of light al)sorbed by solutions of oxy-
hsemoglobin (i cm. in thickness) and of various strengths.

7. II. Hsemoglobia

(a.) To a solution of oxy-h?emoglobin shoAving two well-defined
absorption-bands, add a few drops of ammonium sulphide, and
warm (jenthj, wlien the solution becomes purplish or claret-coloured.

(6.) Study the spectrum, and note that the two absorption-

VI.] THE COLOURED BLOOD CORPUSCLES. 49

bands of oxy-h«>moglohin are replaced by one absorption-band
between ,1) and E, not so deeply shaded, and with its edges less
defined (fig, 24, 4). By shaking the solution very vigorously with
air, and looking at once, the two Ijands may be caused to re-
appear for a short time. Observe the absorption of the light
at the red and violet ends of the spectrum according to the
strength of tlie fluid.

(c.) Dilute the solution, and observe that the single band is
not resolved into two bands, but gradually fades and disappears.

('/.) To a similar solution of oxy-hcTmoglobin, showing two
well-defined bands, add fStokes's fluid, and observe the single
absorption-band of ligemoglobin. Shake the mixture with air and
the two bands reappear.

(e.) Use a solution of oxy-hsemoglobin where the two bands can
Just be se&n, and reduce it with either ammonium sulphide or
Stokes's fluid, and note that, perhaps, no absorption-band of haemo-
globin is to be seen, or only the faintest shadow of one.

(/'.) Compare the relative strengths of the solution of oxy-
haemoglobin and haemoglobin. The latter must he consideral:)ly
stronger to give its characteristic spectrum.

Fig. 25 shows the amount of light absorbed by solutions of
reduced h?emoglobin (i cm. in thickness), and of various strengths.

Stokes's Fluid. — Make a solution of ferrous sulphate ; to it add
ammonia after the previous addition of sufficient tartaric acid to
prevent precipitation. Add about three parts by weight of tartaric
acid to two of the iron salt. Make it fresh ivhen required.

8. Reduction of HbO.^ by Putrefying Bodies. — Fill a test-tube with a dilute
solution ofox3'-lirejnoglobin or blood, add a drop of putrid meat infusit-n, cork
the vessel tiglitly to make it air-tight, and allow it to stand. Ihe oxy-hsemo-
globin is reduced to hfemoglobin, the colour changes to purple-red, and the
Huid shows the sjiectrum of h;i'moglol)in. A better plan is to seal up the
blood in a tube. It neeii not be mixed with putrid matter in order to observe
after a time the reduction.

9. Hsematinonieter. — For accurate observation, instead of a test-tube the
blood is introduced into a vessel with ])arallel sides, the glass plates being
exactly i cm. apart (tig. 31 D). Study this instrument.

10. Hfematoscope (fig. 27). — By means of this instrum.ent the depth of the
stratum of tiuid to be investigated can be varied, and the variation of the
spectrum, with the strength of the solution, or the thickness of the stratum
through which the light passes, at once determined. Study this instrument.

11. III. Carbonic Oxide-Haemoglobin. — Through a diluted solu-
tion of oxy-hsemoglobin or defibrinated blood pass a stream of car-
bonic oxide — or coal gas— until no more CO is absorbed. Note the
florid cherry-red colour of the blood.

O

50

PRACTICAL PHYSIOLOGY.

[VI.

(a.) Dilute the solution in a test- tube and observe its spectrum,
noting that a stronger solution is required than with HbOg, to show

tlie absorption-bands. Two absorp-
tion-bands nearly in the same posi-
tion as those of HbO.,, but very
sUghtly nearer the violet end (fig. 24,
3). ]\rake a map of the spectrum
and bands.

(b.) The bands are not affected by
the addition of a reducing agent,
e.g., ammonium sulphide or Stokes's
fluid. Add these fluids to two
separate test-tubes of tlie solution
of COHb, and observe that the two
absorption bands are not aftected
thereby. There is no diff'erence on
shaking the solution with air, as the
compound is so very stable.

(c.) To a fresh portion of the solution of
carbonic oxide hiemoglobin add a 10 per
cent, sohition of caustic soda and boil =
cinnabar-red colour. Compare this with
a solution of oxy-ha-nioglobin similarly
treated. The latter gives a brownish-red
mass.

('/.) Dilute I cc. of blood with 20 cc. of
closed bv a glass plate. By moving water -f- 20 cc. of caustic soda (sp. gr. i. 34).
CthespacefiFcanlje increased or If the blood contains CO, the fluid first
t^;^Z^^'^ll^l^''T^^ becomes white and cloudy, and presently
for holding suiplns fluid. A. Sup- red. When allowed to stand, flakes form
port. and settle on the surface. Xormal blood

gives a dirty brown colouration,
(c.) Non-Reduction of HbCO. — Repeat the above exjieriment (VL 8) with
carbonic oxide haemoglobin, and note that this body is not reduced by putre-
faction. Or seal up the blood iu a tube.

12. IV. Acid-Haematin.

(a.) To diluted defibrinated blood add a few drops of glacial acetic
acid, and warm getdly, when the mixture becomes brow^nish owing
to the formation of acid hsematin.

{h.) The spectrum shows one absorption-band to the red side of
J) near C (fig. 28, 5), and there is considerable absorption of the
blue end of the spectrum.

(r.) The single band is not affected by ammonium sulphide or
Stokes's fluid. Xote that sulphur is precipitated if Am.^S is used.
If the fluid is made alkaline haemochromogen is formed.

N,B. — If acetic acid alone be used to eftect the change, observe
that only one absorption-band is seen.

Fig. 27. — Hsematoscope of Hermann. F.
Glass plate ; C. Piston-like tube

VI.]

THE COLOURED BLOOD CORPUSCLES

51

13. Acid-Hsematin in Ethereal Solution.

(a.) To undiluted defibrinated blood add glacial acetic acid,
which makes the mixture brown. Extract with ether, shake
vigorously, and a dark-brown ethereal solution of haematin is
obtained. Pour it off and —

{I'.) Observe the spectrum of this solution — four absorption
bands are obtained. The one in the red between C and D, corre-
sponding to the watery acid-hsematin solution ; and on diluting
further with ether a narrow faint one near D, one between D and
E, and a fourth between h and F (fig. 28, 5). The last three
bands are seen only in ethereal solutions, and require to be looked
for with care.

14. V. Alkali-Hsematin.

(a.) To diluted blood add a drop or two of solution of caustic
potash, and warm gently. The colour changes to a brownish-green,
and the solution is dichroic. Or use a solution of acid-hsematin ;
neutralise it with caustic soda until there is a precipitate of
hsematin ; on adding more soda and heating gently, the precipitate
is re-dissolved, and alkali-ha matin is formed.

(b.) Shake (a.) with air to obtain oxy-alkali-haematin. Observe
its spectrum, one absoiption-band just to the red side of the D
line. It is much nearer D than that of acid haematin (fig. 28).
Much of the blue end of the spectrum is cut off.

Red. Oral ge

Yellow.

Blue.

I'l'inni iiiiji iii|mijlhl| iiii|iiTim Lljiii 1 1 1 U II I l.Li 1 11 1 li 1 1 1 ilil' i|i

40 5o bo 70 ■ 80 ()o ICO uo

A a B C D E F

Fig. 28.— Spectra of Derivatives of Hsemogloltiii. 5. Ha'matin in etlier with sulphuric
acid ; 6. Ila-niatiu in an alkaline solution ; 7. Reduced liaiuiatin.

15. Keduced Alkali-Hsematin or Hsemochromogen.

(".) Add to a solution of alkali-hcTmatin a few drops of ammonium
sulphide and warm gently. Note the change of colour = reduced

PRACTICAL PHYSIOLOGY.

[VI.

alkali-hsematin, Stokes's reduced haematin or hsemochromogen,

and observe its spectrum ; two absorption-bands between D and
E, as with HbOg and HbC<J, but they are nearer the
violet end. The first band to tlie violet side of the D
line is well defined, while the second band, still nearer
the violet end (in fact, it nearly coincides with the
E line), is less defined. They disappear on shaking
vigorously with air, and reappear on standing, pro-
vided sufficient ammonium sulphide be added.

Haemochromogen and Hsematin. — Seal up in a glass tube
a solution of oxy-hremoglobin with caustic soda. Hoppe-Seyler
recommends the followiiig method but it is unnecessary. Ar-

Kfio range a tuVje as in fig. 29. Place some ha-moglobiii solution
in A, and into a narrower cu])-sha])ed glass tube (B), with a
long stem place some NaHO, and place B inside A, as shown
in the figure. Draw out the end ot tube A in a gas-flame, and
seal it in the flame. Mix the two solutions. At the end of
three weeks break oft' the narrow end of the tube, and shed
the contents upon a white plate. The contents consist of red

.Q haemochromogen, but the latter, as soon as it is exposed to
the air, becomes brown, and is converted into hsematin,

16. VI. MethEemoglobin (fig. 30).
(a.) To a medium solution of oxy-hsemoglobin add
a few drops of a freshly-prepared strong solution of
ferricyanide of potassium (or a i per cent, solution of
^ potassic permanganate), warm gently, observe the
change of colour, and examine it with a spectroscope.
If the two bands of oxy-haemoglobin are still present,
Fig. 29. — Appara- allow it to stand for some time and examine
^]^ again. If they persist, carefully add more ferri-
cyanide until the two bands disappear. Note
one absorption-band in the red near C, nearly in the same posi-
tion, but nearer I) than the band of acid hsematin ; the violet
end of the spectrum is much shaded. Three other bands are

tui for making
HxTDochromogen.

A a B C D ^ Eb F

40 50 60 70 80 90 100 110

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 II 1 1 1 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 1

liliiiiiiiiiiiiiiliiiil

liii

Fig. 30.— Spectrum of Methfemoglobin in Acid anil Nciitiiil Nn utions.

described, two in the green, and one in the blue, especially in
dihite solutions. On adding ammonia to render the solution
alkaline, the band in the red disappears, and is replaced by a
faint band near P.

VI.] THE COLOURED BLOOD CORPUSCLES. 53

Observe the many-banded spectium of a solution of potassic
permanganate.

(b.) To an alkaline solution of metlifemoglobin add ammonium
sulphide. Thi^ gives the spectrum first of oxy-haemoglobin and
then of liiemoglobin : and on shaking with air, oxy-hamoglobin is
formed.

(c) To a sohition of oxy-lia?moglohiT) add a crystal or two of potassic
chlorate ; dissolve it with the aid of geutle heat ; after a short time the spec-
trum of methffiuioglobiu is obtained.

('?.) Action of Nitrites. — To diluted defibrinated ox-blood, or
preferabl> that of a dog, add a few drops of an alcoholic solution of
amyl nitrite. The blood immediately assumes a chocolate colour
{Gam'jee).

(e.) To another portion of diluted blood add a solution of
potassic or .sodic nitrite. Observe the chocolate colour.

(/.) To jwrtions of (':7.) and (e.) add ammonia; the chocolate
gives place to a red colour.

((/.) Observe the spectrum of{d.) and (e.). The band in the red is distinct,
and is best seen when the solution is of such a strength that oidy the red rays
are transmitted. On 'iilution, other bands are seen in the green. Add
amnninia, ami witli the change of colour described in {/.) the spectrum
changes as desciibed in {a.). Add aiiuuonium sulphide or Stokes's fluid, the
sjiectruni of reduced haemoglobin appears, and on shaking up with air, the
bands of oxj'-haemoglobin apjjear.

(/(.) Crystals of Methsemoglobin. — To a litre of concentrated solution of
hamoglobin add 3-4 cc. of a concentrated solution of fenicyanide of j)Citassium
and also a quarter of a litre of alcoliol, and freeze the inixture. After two
daj's, brown crystals of methaemoglobin separate.

(/. ) To a few cc. of defibrinated blood (rat, guinea-pig), add an equal
numljer of drops of amyl nitrite, and shake the mixture vigorously for a
minute or two = dark chocolate tint of methaemoglobin. A drop of this fluid
transferred at once to a slide, and covered, yields crystals of methasnioglobin
{ifalliburton).

17. VII. Haematoporphyrin (iron-free hij?matin CjglligXgC')-
(a.) To some strong sulphuric, acid in a test-tube add a few

drops of undiluted blood (about 5 drops of blood to 8-10 cc.

of II^SO^) ; mix by shaking, when a clear violet-red cr purple-red

fluid is obtained.

(h.) Observe two absorption-bands, one close to and on the red

side of D, and a second half-way between 1) and L.

(c.) To some of this violet-red solution add a large excess of water, whicli
throws down part of the hnnmatopi.r])hyriii in the form of a brown precipitate,
which is more copious if the acid be neutralised with an alkali, e.y., caustic
soda. Dissolve some of the brown deposit in caustic soda, and examine it
spectroscopically.

54 PRACTICAL PHYSIOLOGY. [VI.

(d.) The spectrum shows four absorption -bands ; a faint band midway be-
tween C and D, another similar one between D and E, but close to D ; a third
band near E ; and a fourth one, darkest of all, occupying the greater part of
the space between b and F, but nearer the former.

In all cases make drawings of what you see, and compare them with the
table of characteristic spectra suspended in the laboratory.

18. Picro-Cannine. — Its spectrum closely resembles that of
HbOg, but the two bands are much nearer the violet end, one
being midway between D and E, and the other to the violet side of
E. The bands are unchanged on addition of Am^S or Stokes's
fluid. The solution does not give proteid reactions.

ADDITIONAL EXERCISES.

19. Prolonged Action of Methsemoglobin-forming Reagents. — Allow
KMnOj, K^jFeCyg, iodine, amyl or potassium nitrite or glycerine to act on Hb02
for some days at 40° C. Methaemoglobin is first formed, then hrematin. The
latter is partially precipitated. Precipitate may be washed with water and
dissolved in dilute acid or alkali. In the case of KjFeCye the solution becomes
cherry-red, and contains cyan-haematin. Its spectrum shows one broad band,
like that of Hb, between D and K, unchanged on shaking with air. In the case
of amyl nitrite the final product in solution has a spectrum like that of HbOj,
unchanged on treatment with Am^S (? HbNO).

Hb( >2 solution or dilute blood left on the water-bath at 40° C. for some days
shows first a partial formation of methaemoglobin and later becomes Hb. It
does not become converted into haematin (/. A. Menzies).

20. Effect of Sodium Fluoride. — To HbO.2 solution or diluted blood, add a
few dro])S of i per cent. NaFl solution, and keep at 40° C. until the colour
changes from scarlet to a rich crimson. Examine the spectrum. In addition
to traces of the HbO, bands, there will be seen two bands, one very distinct to
the red side of D, slightly nearer the red than the band of alkali-haematin, the
other, not easily seen, to the violet side of E. On addition of Am^S, the spec-
trum changes first to that of HbO^, then Hb.

21. Effect of Acids. —(rt.) To 15 cc. dilute blood which gives a well-marked
spectrum of HbO^, add 5 drops of i ])er cent. HCl (or other acid). The colour
changes to brown, and the spectrum to that of acid ha-matin. Add ammonia,
the spectrum becomes that of alkaline metlntmoglobin, and, on addition of
Am^S, the solution changes to HbO, then Hb. But, if Am.jS be added with-
out ])revious addition of ammonia, the spectrum becomes that of ha?mo-
chromogen first becoming Hb on standing, and then HbOj appears on shaking
the solution with air.

{h.) Place 15 cc. of solution of pure HbOa with well-marked spectrum in
each of five test-tubes. To these add i, 2, 5, 10, and 15 drops of i percent.
HCl respectively. Place all on a water-bath at 40° C. for 24 hours, or longer
if necessar}'. In some of the tubes a precipitate of lupiuatin will be found, and
in one of these the supernatant fluid will be colourless, and will give proteid
reactions. Decant the colourless fluid, and collect and wash with water the

VII.]

WAVE-LENGTHS.

55

haematin i)recii)itate. Dissolve the hiematin in water containing a trace of
HCl. It will give the spectrum ot acid- hsema tin. To one portion add some
of the decanted fluid and a few drops Am_jS, to another add Am^S only. In
the former case the h;t?mochromogen formed will gradually become partially
converted into Hb (prove by shaking with air and obtaining spectrum of
HbO.^), in the latter case the hsemochromogen will remain unaltered.

LESSON VII.

WAVE-LENGTHS— DERIVATIVES OP HEMO-
GLOBIN—ESTIMATION OP HEMOGLOBIN.

Spectroscopic Determination of Wave-Lengths. — Use Zeiss's
spectroscope, which is provided with an ilhiminated scale for this
purpose.

1. W.L. of Absorption-Bands of Oxy-Haemoglobin.

(a.) Arrange the apparatus as shown in fig. 31. A is the

Fig. 31. — Anangement of the Speotrnsrope for neterniiiiing Wave-I,enutlis. .4. Tele-
scope: B. CollimMtiir tube: C. Scale tube : D. lliEmatinoinuter.

telescope tlirough which the observer looks at tlie spectrum
obtained by the light passing through 13, and dispersed by the

56 PRACTICAT. PHVSTOLOGY. [vil.

flint-glass prism in the centre of the apparatus. In C is fixed
a scale photographed on glass and illuminated by a fan-tailed
burner. D is the hfematinometer containing the dilute blood.

(h.) Throw a piece of black velvet over the prism ; light both
lamps . look through A ; adjust the slit in li, and the telescope
in A, so as to get a good view of the spectrum, and over it the
image of the scale. D is supposed not to be in position at first.
On platinum vsdre, burn common salt in the flame to get the yellow
sodium line D. Adjust the scale so that this line corresponds to
the figures 58.9 on the scale, and fix the spectroscope tubes (A
and C) in this position ; the scale is now accurately adjusted for all
other parts of the spectrum.

" The numbers on the scale indicate wave-lengths expressed in
one hundred thousandths of a millimetre, and each division indi-
cates a difference in wave-length equal to one hundred thousandth
of a millimetre '"' [Gamgee.)

Thus, Fraunhofer's line, D, which corresponds to division 58.9
of the scale, has a wave-length of 589 millionths of a millimetre.
The wave-lengths of Fraunhofer's lines are : — A = 760.4, B = 687.4,
0 = 656.7,0 = 589.4, E= 527.3, F = 486.5.

(c.) Using one of the blank maps supplied with Zeiss's spectro-
scope—the maps correspond to the scale seen in the spectroscope —
fill in, in wave-lengths, the position of Fraunhofer's lines B to F.

{d.) Use a dilute solution of blood or hiemoglobin — i part in
1000 of Avater is best — and place it in the haematinometer, D,
which is placed in position between the flame and the spectroscope,
as shown in fig. 31. The distance between the parallel faces of D
is I cm. .The spectrum shows the two absorption-bands of oxy-
haemoglobin between D and E. Tlie narrower, sharper, and blacker
band near D has its centre corresi^onding with the W.L. 579, and
it may conveniently be expressed by the letter a of the oxy
haemoglobin spectrum.

The other absorption-band near E, and conveniently designated
P, is broader, not so dark, and has less sharply defined edges than
a. Its centre corresponds to tlie W.L. 543.8. Notice that the
other parts of the spectrum are seen, there being only slight
cutting off of the red, and a slightly greater absorption of the violet
end.

(e.) Work Avith a stronger solution of blood, and observe how
the two bands become fused into one, while more and more of the
red and violet ends of the spectrum are absorbed as the solution is
made stronger, until finally only a little red light is transmitted.

2. W.L. of Absorption-Band of Reduced Hb.

(a.) Adjust the apparatus as before, but reduce the oxy-hasmo-

VII.]

WAVE-LENGTHS.

57

globin solution with Stokes's fluid — noticing the change of the
colour to that of purplish or claret — until a solution is obtained
which gives the single characteristic absorption-band of reduced
Hb. Tills is usually obtained with a solution of Hb of about 0.2
per cent.

(b.) Observe the single absorption-band less deeply shaded, and
with less defined edges between 1) and E, conveniently designated
by the letter a. It extends between W.L. 595 and 538, and is
not quite intermediate between D and E ; is blackest opposite
W.L. 550, so that it lies nearer D than E. Both ends of the
spectrum are more absorbed than with a solution of oxy-hsemo-
globin of the same strength. On further dilution of the solution,
the band does not resolve itself into two bands, but simply
diminishes in width and intensity (fig. 32, 5).

A a Ji c D Eh F

\Y\ ? '

65 V
1 rri 1 1 1 1 1 1

1 1 1 I'l 1

60 45

1 1 1 r 1 1 r 1 1

■40

III!

\ 1

1 i

JBBk

y

- ni

iB^H^ni

1 1 II

km

If^H^BHIIIHPI

1 1 1

IflH^HHp

1 1 1 ]

li

.abhhM

lO'sJo ^5 T

1 III j 1 1 1 1 1

3 « e'o

^' i~

1 1 1 1 1 1 i 1 1

60 ♦'

III

40

1

Fig. 32.— The Spectra of Oxy-Hseninglobiu (i, 2, 3, 4), 1=0.1, 2=0.2, $=.37, 4 = . 8 per cent.
of f )xy-H8einr)glohiii, Haemoglobin (5), and'Carbonic O.xide Hafmoglobin (6). Wave-
lengths added. The numbers attached to the scale indicate wave-lengths expressed
in loo.oooths of a millimetre.

3. W.L. of the Spectrum of Carbonic Oxide Heemoglobin,

(".) Use a dilute solution of carbonic oxide haemoglobin of such

strength as to give the two characteristic absorption-bands.

(/'.) Observe the two bands, a and P, like those of HbO.„ but
both are very slightly more towards the violet end of the spectrum.
a extends from about W.L. 587 to 564, and /S from 547 to 529,

(c.) Xo reduction is obtained by reducing agents (tig. 32, 6).

58

PRACTICAL PHYSIOLOGY.

[VII,

4. Preparation of Hsematin (C3. Hj^N^OjFe).

{a.) Make defibrinated blood into a paste with potassic carbonate and dry
it on a water-bath. Place the paste in a flask, add 4 volumes of alcohol, and
boil on a water-bath. Filter, and an alkaline brown solution of ha'matin is
obtained. Re-extract the residue several times with boiling alcohol, and mix
the alcoholic extracts. The solution is dichroic.

{b.) Acidify the alkaline filtrate of («.) with dilute sulphuric acid, filter,
and keep the filtrate. Observe the spectrum of acid hiematin in the filtrate
(figs. 28, 5, and 33, 5),

A a S C

Fig. 33. — Spectra of some of the Derivatives of Hremot'lobin. i. Hsematin in allvaline
solution; 2. The same, but more concentrated ; 3. Hseniochromogen ; 4. Methjemo-
globin ; 5. Acid htcmatin (acetic acid) ; 6. Acid hteinatin in ethereal solution.

(r. ) Add excess of ammonia to the acid filtrate of (ft.), and filter off the pre-
cij)itate, keej) the filtrate, and olxserve that it is dichroic. Observe the
spectrum of alkali h:i'matin in the filtrate (fig. 28, 6).

('/. ) Evaporate the filtrate from ('•.) to dryness on a water-bath. Extract
the residue with boiling water. The black residue is washed on a filter with
distilled water, alcohol, and ether, and dried in a hot chamber at 120° C.
This is nearly pure hamatin.

('-. ) It is convenient to keep in stock hrematin pref)are(l as follows : — Ex-
tract defibi'inated blood or blood-clot ox or sheep) with rectified s])irit con-
taining })ure sulphuric acid (i : 20. ) Filter ; the solution gives the s])ectrum
of acid hrematin. Add an equal volume of water and then chloroform. The
chloroform liecomes brown, and there is a preci]iitate of proteids. Sejtarate
the chloroform extract, wash it with water to remove the acid. Sej)arate the
chloroform, and allow it to evajiorate. The dark brown residue is inijture
h;vmatin. When dissolved in alcohol and caustic soda it gives the spectrum
of alkali hiematin, and on adding ammonium sulphide that of haniochroniogen.
If it is dissolved in b\SOj, and filtered through asbestos, the red filtrate gives
the spectrum of ha;mato-porphyrin {MacAIuun).

VII.] ESTIMATION OF HEMOGLOBIN. 59

5. Hsemin Crystals. — Place some powdered dried blood on a
glass slide, or smear some blood on a slide, allow it to dry, add a
crystal of sodium cliloride, and a few
drops of glacial acetic acid. Cover
with a cover-glass, and heat until
bubbles of gas are given off. After
cooling, brown or black rhombic
crystals of htemin are seen with a
microscope (fig. 34). To preserve
them irrigate with water, dry and ^ „ - r. . 1

, . % ,11 Fig. 34.— Hicniiii Crystals.

mount :n Canada balsam.

6. Detection of Blood-Stains. — Use a piece of rag stained with
blood.

(a.) Moisten a part of the stain with glycerine, and after a time
express the liquor, and observe it microscopically for blood-cor-
puscles.

{h.) Tie a small piece of the stained cloth to a thread, place the
cloth in a test-tube with a few drops of distilled water, and leave
it until the colouring-matter is extracted. Withdraw the cloth by
means of the thread. Observe the coloured fluid spectroscopi-
cally.

(c.) Boil some of the extract with hydrochloric acid, and add
potassic ferrocyanide ; a blue colour indicates the presence of iron.

((/.) Use the stain for the hcemin test, doing the test in a watch-
glass.

7. The Hsemoglobinometer of Cowers is used for the clinical
estimation of hpemoglobin (fig. 35). The tint of the dilution of a
given volume of blood with distilled water is taken as the index of
the amount of haemoglobin. The colour of a dilution of average
normal blood (one hundred times) is taken as the standard. The
quantity of haemoglobin is indicated by the amount of distilled
Avater needed to obtain the tint with the same volume of blood
under examination as was taken of the standard. On account of
the instability of a standard dilution of blood, tinted glycerin
jelly is employed instead. The apparatus consists of two glass
tubes of exactly the same size. One contains (D) a standard of
the tint of a dilution of 20 c.mm. of blood, in 2 cc. of water (i in
100). The second tube (C) is graduated, 100° = 2 cc. (100 times
20 c.mm.).

{a.) Place a few drops of distilled water in tlie bottom of the
graduated tube (C).

{■>.) Puncture the skin at the root of the nail with the shielded
lancet (F), and with the pipette (B) suck up 20 c.mm. of the blood,
and eject it into the distilled water, and rapidly mix them.

6o

PRACTICAL PHYSIOLOGY.

[VIL

(<•.) Distilled water is then added drop by drop (from the pipette
stopper of a bottle (A) supplied for that purpose) until the tint of
the dilution is the same as that of the standard. The amount of
water wliich has been added {i.p., the degree of dilution) indicates
the amount of haemoglobin.

" Since average normal blood yields tlie tint of the standard at
loo" of dilution, the number of degrees of dilution necessary to

Fro. 35.— A. Pipette bottle for distilled water : B. Capillary pipette : C. Graduated tube.
D. Tube with standard diluti<jn ; F. Lancet for pricking the linjjer.

obtain the same tint with a given specimen of blood is the per-
centage proportion of the hfemoglobin contained in it, compared to
the normal. For instance, the 20 c.mm. of blood from a patient
with anaemia gave the standard tint of 30° of dilution. Hence it
contained only 30 per cent, of the normal quantity of haemoglobin.
By ascertaining with the haemacytometer tiie corpuscular richness of
the blood we are al^le to compare the two. A fraction of which
tlie numerator is the percentage of haemoglobin, and the denomina-
tor the percentage of corpuscles, gives at once the average value per
corpuscle. Thus the blood mentioned above containing 30 per cent,
of haemoglobin contained 60 per cent, of corpuscles ; hence the
average value of eacli corpuscle was f^ or half of the normal.
Variations in the amount of haemoglobin may be recorded on the
same chart as that employed for the corpuscles."

" In using the instrument, the tint may be estimated by holding
the tubes between the eye and the window, or by placing a piece
of white paper behind the tubes ; the former is perhaps the best.

VII.]

ESTIMATION OF H.EMOGLOBIN'.

6l

In i)ractice it Avill be found that, during 6 or 8 degrees of dilution,
it is difHculc to distinguish a difference between the tint of tlie
tubes. It is therefore necessary to note the degree at which the
colour of the dilution ceases to be deeper than the standard, and
also that at which it is distinctly paler. The degree midway
between these two will represent the haemoglobin percentage."

ADDITIONAL EXERCISES.

8. Fleischl's HaBmometer. — This apparatus (fig. 36) consists of a horse-shoe
stand with a pillar beaiing a retiecting surface (S) and a platform. Under
the table or platform is a slot carrying a glass wedge stained red (K), and
moved by a wheel (R). On the i)latlorm (.M) is a small cylindrical vessel (G),

Fig. 36. — Fleischl's H»u)ometer.

divided into two conii)artments (« and a') by a vertical septum. In one
compartment is placed pure water, and in the other the blood to be investi-
gated. A scale (P) on the slot of the instrument enables one to read off
directly the percentage of h:i-nioglobin.

(a.) Fill with a pipette the comjjartment («') over the wedge with distilled
water, and see that the surface of the water is quite level with the top of the
cylinder. Fill the other compartment (a), that for the blood, about one-
quarter with distilled water.

62

PRACTICAL PHYSIOLOGY.

[VIL

(b.) Prick the finger as in 7 with the instruraSnt supplied for the purpose.
Fill the short automatic capillary pipette tube with blood. Its capacity is
6.5 c.mni. In filling the tube, hold it horizontally. See that no blood
adheres to the surface of the tube. This can be done by having the i)ipette
slightly greasy on the outer surface.

(c. ) Dissolve the blood obtained in (b.) in the water of the blood-compart-
ment ('!-), washing out every trace of blood from the pipette. Mix the blood
and water tlioroughly. Clean the pi{)ette. Then fill the blood compartment
exactly to the surface with distilled water, seeing that its surface also is per-
fectly level.

{r/.) Arrange a candle in front of the reflector (S) — which is white, and with
a smooth matt surface made of plaster-of- Paris — so as to throw a beam of light
vertically through both compartments. Look down vertically upon both
compartments, and move the wedge of glass by the milled head (T) until the
colour in the two comi)artments is identical. Read off the scale, which is so
constructed as to give the percentage of luemoglobin.

9. Bizzozero's Chromo-Cytometer. — The chief part of the instrument con-
sists of two tubes (fig. 37, ab, cd), working one within the other, and closed
at the same end by glass discs, while the other ends are open. The one tube

can be completely screwed into
the other, so that both glasses
touch. Connected with the outer
tube is a small open reservoir (?•),
from which fluid can pass into
the variable sjiace between the
two glass plates at the ends of
the tubes. By rotating the inner
tube, the space between the two
glass plates can be increased or
diminished, on the principle of
Hermann's haanatoscope, and
the screw is so graduated as to
indicate the distance between
the two ])lates, i.e., the thick-
ness of fluid between them. Each
complete turn of the screw = 0.5
mm., and the subdivisions on it
are so marked — 25 to one turn
(index fig. 37 erf) — that each

subdivision of the index =—^

Fig. 37— General View of the Chromo-Cytonieter. ,,,, ,, . •>

aft and cd. Two tubes, the one fits inside the =o.o_2 mm. When the inner
other; r. Reservoir eomniunicatin,' witli the tube is screwed home and touches
space between c and b when cd is screwed into l\^Q ^j^ss disc in the outer tube,
ao ; cr. Milledliead :ind index scale to the left i.i, • 1 ,. j 4. „ j.i i

of it, for the tinted glass ; m. Handle. ^^e index stands at o on the scale.

It the instrument is to be used
merely as a cytometer, these parts suffice ; but if it is to be used as a chromo-
meter, the coloured glass must be used. The instrument is also provided
with small glass thimljles with flat bottoms, containing 2 and 4 cc. re.s])ectively;
a pipette graduated to hold h and i cc, and another pipette for 10 and 20
c.mm., the latter provided with an india-rubber tube, to enable the fluid
to be sucked up readily ; a bottle to hold the saline solution, and a glass
stirrer.

Method of Using the Instrument as a Cytometer. — i . By means of the
pipette place 0*5 cc. in normal saline solution in a glass thimble.

VII.]

ESTIMATION OF H.EMOGLOBIX.

63

2. With a lancette or needle puncture the skin of the finger at the edge of
the nail.

3. With the ]>ij)ette suck up exactly 10 c.mm. of blood. Mix thLs blood witli
the .5 c cm. saline solution, and suck part of the latter several times into the
capillary tube, so as to re-
move every trace of blood
from the jiipette. Mix the
fluids thoroughly. Care-
fully cleanse the pipette
with water.

4. Pour the mixture into
the reservoir (/) of the in-
strument. Gradually rotate
the inner tube, and as the
two glass discs separate,
the fluid passes into the
space between them.

5. In a dark room light
a stearin candle, place it at
a distance of I i metres, and, taking the instrument in the leiV hand, bring
the open end of the tubes to the right eye. With the right hand rotate the
inner tube to vary the thickness of the column of fluid, and so adjust it
until the outlines of the upper three- fourths of the flame can be distinctly
seen through the stratum of fluid. Vary the position of the inner screw .so
as to determine accurately when this occui'S. Read ofl" on the scale the
thickness of the stratum of fluid.

Fig. 38. — Showina how cd fits into ab. zz. Plates of gla.ss
closing the ends of ah anil cd: other letters as in

flS- 37-

Graduation of the Instrument as a CytornfJer. — In this instrument the
graduation is obtained from the thickness of the layer of blood itself, and the
amount of hpemoglobin is calculated directly from the thickness of the layer
of blood which is necessary to obtain a certain optical effect, viz., through the
layer of blood-corpuscles to see the outlines of a candle-flame placed at a
certain distance.

From a number of investigations it appeai-s that in healthy blood the out-
lines of the flame of a candle are distinctl* seen through a layer of the mixture
no

of blood — mm
100

in thickness.

Let the number no corres]K)nd to i, or to 100 parts of hsemoglobin ; then
it is easy to calculate the relative value of the subdivisions of the scale on the
tube of the instrument. Let q = the degree of the scale for nomial blood ;
g', that for the blood being investigated ; e, amount of haemoglobin in the
former ; and c\ the amount sought for in the latter.

Assuming that the product of the quantity oi haemoglobin and the thickness
of the stratum of blood is constant, so that

Then we have

eg = e' ^.

• eg

e =-f
9-

Let us assume that the blood investigated gave the number 180 ; then,
using the above data, we have : —

icox no 11.000

iSo

180

= 61.1.

64

PRACTICAL PHYSIOLOGY.

[VII

The blood, therefore, contains 61.1 hemoglobin. The following table gives
the proportion of haemoglobin, the normal amount of hi^moglobin being taken
as= 100 : —

Cytometer Scale.

Hieinoglobiu

Cytometer

Scale.

liienioglobin

no

. lOO.O

170

• 64.7

120

91.6

I So

. 61. 1

130

. 84.6

190

• 57.9

140

. . 78.5

200

• 55-0

150

• 73-3

210

• 52.4

160

. . 68.7

220

50.0

Using the Instrument as a Chromometer. — The blood is mixed with a
known volume of water, whereby the haemoglobin is dissolved out of the red
corpuscles and the Huid becomes transparent. The quantity of hemoglobin is
calculated from tlie thickness of tlie stratum of fluid required to correspond
exactly to the colour-intensity of a coloured glass accnm])anying the instru-
ment. The latter is coloured of a tint similar to a solution of hjemoglobin,
and is fixed to the instrument by means of a suitable brass fixture.

1. Fix the coloured glass with its brass frame in the instrument.

2. Mix 10 c.mm. blood with .5 cc. distilled water. In a few seconds a trans-
parent solution of haemoglobin is obtained.

^. Pour this solution into the reservoir (r), and rotate the inner tube so
that the fluid passes between the two glasses. Direct the instrument towards
a white light or the sky, not towards the sun, and compare the colour of the
solution with the standard coloured glass, a procedure which is facilitated by
placing a milky glass between the source of light and the layer of blood, so as
to obtain difi'use white light. ^Vhen the tM'o colours a]>pear to have as near
as possible the same intensity, read off' on the scale the thickness of the layer
of blood, and from this, by means of the accompanying table, ascertain the
con-esponding amount of htemoglobin.

This is done in the same way as for the cytometer, but the graduation is
different, as in the one case we have to do with a candle flame, and in the
other with a coloured glass.

In very pronounced cases of anaemia, even with a layer of blood 6 mm. in
thickness, owing to the limits of the instrument, the intensity of the mixture
of blood may be less than that of the coloured glass. In such a case,
instead of 10 c.mm. of blood, use 20 c.mm.

Graduation of the ChromnmrJer. — As the coloured glass has not absolutely
the same intensity of colour in all chromometers, one must first of all estimate
the colour-intensity of the glass itself. This is most easily done by ascertain-
ing in a given specimen of blood what degree ol the chromometer corresponds
to the scale of the cytometer of the same blood.

Sup>pose that a specimen of blood by means of the cytometer gave no, and
by the chromometer 140 ; the number 1 10 of the cytometer = 100 h;-cmoglobin,
so that the chromometer numlier 140 must also be = 100. With the aid of
the_ formula (}). 63) a similar table can be constructed for the chromometer.
Suppose the bloofl investigated = 280 ; then by the aid of the formula and
the data from normal blood we have —

100 X 140 14,000

280

280

= 50.

This blood, therefore, contains 50 parts of haemoglobin.

Example. — Blood gives 130 with the cytometer and 190 with the chromo-
meter ; what is the initial number of the chromometer graduation correspond-
ing to 100 parts of hseraoglobin ?

VII.] Estimation of hemoglobin. 65

If 130 I'cytometer) corresjionds to 190 (chromometer) then no cytometer
(i>., graduation coriesponding to loo parts ol hemoglobin) corresponds to x
chromometer graduation :

190. no 20,900 . _

\\0: IQO = 1 10 : .X-. . x ■-= -^ = — ^^— = 160.7.

130 130

Blood containing 100 parts haemoglobin will corresi)ond to 160 of the chromo-
meter scale, and beginning with this number as a basis, with the aid of our
formula it is easy to construct a table showing the relation.

Whilst the value of the cytometer scale remains the same for every instru-
ment, the chromometer scale varies with each instrument, as the colour-
intensity of tlie glass is not necessarily the same in all. But it is easy to
construct a scale for each instrument by investigating a sjiecimen of blood
and comparing it with the cytometer graduation as indicated in tiie foregoing
paragraph.

I'recaations to he Oh'^crved in Using the Instmment. — The exact quantity of
the several fluids must be carefully measured ; eva])oration must be prevented
by covering the blood-mixture. Further, do not look at the fluid too long at
a time, as the eye becomes ra{)idlj- fatigued. Further, the operation must be
carried out not too slowly, as the saline solution only retards the coagulation
of the blood, and does not arrest it.

In cases of leukiemia, where there is a large number of white corpuscles
rendering the mixed fluid opaque, the corpuscles may be made to disappear by
adding a drop of a very dilute caustic potash. If the opacity does not disappear
by the addition of this substance, then the 0])acity is due to the presence of
fatty granules in the blood, so that by this means we can distinguish lipsemia
from leukaemia.

Bizzozero claims tliat when the instrument is used as a cytometer the mean
error is not greater than o. 3 per cent.

10. Preparation of Haemoglobin {dog^s or hnrse's blood). — Centrifugalise
Altered fresh defilirinated dog's blood, and when the corpuscles have subsided
jiour ofl" tlie clear serum. Mix the corpuscles with .5-2 per cent, solution of
NaCl, and centrifugalise again. Repeat the process until the washings con-
tain only a trace of proteid, or begin to be tinged red from the solution of the
blood-corpuscles.

Mix the magma of corpuscles with 2-3 volumes of water saturated with
acid-free ether. Tlie corpuscles swell up, become almost invisilile, and the
solution becomes clear. With the utmost care add, stirring all tlie time, i per
cent, solution of acid sodic sulphate until the blood appears turbid like fresh
blood. The stromata of the cor])U.scles are thereby caused to shrivel, and when
they are centrifugalised for a long time, they run together, and can thus be
separated. Pour ofl' the clear fluid, cool it to o", add one-fourth of its volume
of pure alcohol previou.sly cooled to o" or lower. Shake up the whole, and let
it stand for twenty-four hours at 5^-15^. As a rule, the whole passes into a
glittering crystalline mass. Place it in a filter cooled to o\ and wash it with
ice-cold 25 jjer cent, alcohol. Redissolve the crystals in a small quantity
of water, and recrystallise with alcohol as before. The crystals are spread on
plates of porous porcelain, and dried in a vacuum over sulphuric acid.

11. Amount of Hapmoglobin in Blood— Colorimetrlc Method (Hoj)pe-
Seylers method]. — A standard solution of pure haemoglobin diluted to a
known strength is used, and with this is compared the tint of the blood
diluted with a known volume of distilled water.

(a,) A standard solution of hajmoglobin of known strength is supplied (sw/>ra).

B

66

PRACTICAL PHYSIOLOGY.

[VIL

{b.) Spread a sheet of white paper on a table in a good light o])j)Osite a
window, and on it jilace two hitmatinometers side by side (fig. 31, D;. See
that they are water-tight. If not, anoint the edges of the glass plates-Avith
vaseline to make them water-tight.

(c. ) Take 10 cc. of the standard solution of haemoglobin and dilute it with
50 cc. of water, and place it in one of the haematinometers.

((/. ) Weigli 5 grams of the blood to be investigated, and dilute it with
water exactly to 100 cc.

(e. ) Place 10 cc. of this deeper tinted blood {d.) into the second hsematino-
meter.

(/. ) Fill an accurately graduated burette with distilled water, place it over
the second hiematinometer (f. ), and dilute tlie blood in it until it has precisely
the same tint as the standard solution in the other haematinometer. Note the
amount of water added. The two solutions must now contain the same
amount of haemoglobin.

EKam]ile {HujipeSeijler). — 20. 1S6 grams of defibrinated blood were diluted
with water to 400 cc. To the 10 cc. of this placed in a ha-matinometer, 38

Fig. 39.

cc. of water had to be added to obtain the same tint as that of the standard
solution, so that the volume of water which would require to be added to
dilute the whole 400 cc. would be 1520 cc, thus —

10 : 400 : : 38 : a;
X = 1520 cc.

By adding 1520 cc. of distilled water to the 400 cc. of blood solution, we get
1920 cc. of the same tint or degree of dilution as the standard solution.

The standard solution on analysis was found to contain 0.145 grams of
hsemoglobin in 100 cc, so that the total amount of hoimoglobin in the diluted
blood is found, thus —

100 : 1920 : : 0.145 * ^
X = 2.784 grams.

VIII.] SALIVARY DIGESTION. 6"]

Since, however, tliis amount of hsemoglobin was obtained fi'oni 20. i86 grams
of the original blood, the amount in 100 parts will be found as follows : —

20.186 : 100 : : 2.784 : x
0: = 13. 79 grams per cent.

12. Microspectroscopes. — "When very small quantities of fluid are to be
examined, they are ]ilaced in small vessels made by fixing short lengths of
barometer tubing to a glass slide. Use either the instrument of Browning or
that oi Zeiss (tigs. 39, 40).

The instrument is in reality an eyepiece with a slit mechanism adjustable
between the field glass and eye glass of an ocular. The instrument is fitted
into the tube of a microscope in place of the eyepiece. It consists of a drum
(A) with a slit adjustable by means of the screws H and F (fig. 40). Within
the drum tliere is also a prism whereby light admitted at the side of the drum
is totally reflected towards tlie eye of the observer. Above the eye glass is
placed an Amici prism of great dispersion, which turns aside on tiie ])ivot (K)
to allow of the adjustment of the object. It is retained in position by tlie
catch (L). At N is placed the scale of wave-lengths, and its image can be
projected on the spectrum by the mirror (0). The scale is adjusted relative
to the spectrum by tlie screw P. The scale is set by the observer so tliat
Fraunhofer's line D corresponds to 58.9 of the scale.

The fluid to be examined is placed in a suitable vessel on the stage of the
microscope, and light is transmitted through it.

LESSON VIII.
SALIVARY DIGESTION.

1, To Obtain Mixed Saliva. — Rinse out the mouth with Avater
an hour or two after a meal. Inliale the vapour of ether, glacial
acetic acid, or even cold air tlirough the mouth, which causes a
reflex secretion of sahva. In
doing so, curve the tongue '\ ^^
so as to place its tip behiml "'^if^..
the incisor teeth of the upper
jaw. Or chew a piece of
caoutchouc. In a test-glass "Wi-i^y^^
collect tlie saHva Avith as few
air-bu])b]es as possible. If
it be turljid or contain much ^ _
froth, filter it through a small '^ '■* " ''•'^ '" ''^'
filter (p. 69). Fig. 41.— Microscopic Appeiiiuiii.es ..i .-..n. a.

2. I. Microscopic Exam-'nation. — "With a high power observe
the presence of (i) squamous epithelium, (2) salivary corpuscles,

^^^.

68 PRACTICAL PHYSIOLOGY. [VIIL

(3) perliaps d/'bris of food, (4) possibly air-bubbles, and (5) fungi —
especially various forms of bacteria (fig. 41).

II. Physical and Chemical Characters (sp. gr. 1002 -1006).

(a.) Observe its appearance — it is colourless and either trans-
parent or translucent — and that when poured from one vessel to
another it is glairy, and more or less sticky. On standing, it
separates into two layers ; the lower one is cloudy and turbid, and
contains in greatest amount the morphological constituents.

(b.) Its reaction is alkaline to litmus paper.

{c.) Add acetic acid = a precipitate of mucin not soluble in
excess. Filter.

(d.) With the filtrate from (c), test for traces of proteids
(serum-albumin and globulin) with the xanthoproteic reaction and
Millon's test.

(e.) To a few drops of saliva in a porcelain vessel add a few
drops of dilute acidulated ferric chloride = a red colouration due to
potassic sulpho-cyanide. The colour does not disappear on heat-
ing, or on the addition of an acid, but is discharged by mercuric
chloride, Meconic acid yields a similar colour, but it is not
discharged by mercuric chloride. The sulpho-cyanide is pre-
sent only in parotid saliva, and is generally present in mixed
saliva,

(/.) Test a very dilute solution of j^otassic sulpho-cyanide to
compare with (e.).

(g.) Gscheidlen's method. Dip fiiter paper in weak acidulated
(HCl) ferric chloride solution, and allow it to dry. Contact with a
drop of saliva gives a reddish stain.

(//.) The salts are tested for in the usual way (see "Urine").
Test for chlorides (HNO3 and AgNOg), carbonates (acetic acid),
and sulphates (barium chloride and nitric acid).

(i.) Nitrites are often present in saliva. Add a little of the saliva to starch
paste, containing a little suljihiiric acid and iodide of potassium, when, it
nitrites be present, an intense blue colour is produced.

(,;'.) To diluted saliva add a few drops of suljihuric acid, and then nieta-
diamido benzol. Yellow colour indicates the presence of nitrites. This re-
action does not succeed in all cases.

3. Digestive Action.

Starch Solution. — Place i gram of pure potato starch in a
mortar, add a few cc. of cold water, and mix well with tlio starch.
Add 200 cc. of boiling water, stirring all the while. Boil the
fluid in a flask for a few minutes. This gives .5 per cent,
solution.

Action of Saliva on Starch (Ptyalin, a diastatic enzyme).

(a.) Dilute the saliva with Jive volumes of water, and filter it.

VIII.] SALIVARY DIGESTION. 69

This is best done througli a filter perforated at its apex by a pin-
hole. In this way all air-bubbles are got rid of. Label three
test-tubes A, E, and C. In A place starch mucilage, in B saliva,
and in C I volume of saliva and 3 volumes of starch mucilage.
Place them in a water-bath at 40° C. for ten minutes. Test for a
reducing sugar in portions of all three, by means of Fehling's
solution. A and B give no evidence of sugar, while C reduces
the Fehling, giving a yellow or red deposit of cuprous oxide.
Therefore, starch is converted into a reducing sugar by the saliva.
This is done by the ferment ptyalin contained in it.

{fj.) Test a portion of C with solution of iodine ; no blue colour
is obtained, as all the starch has disappeared, being converted
into a reducing sugar or maltose.

('•.) Make a f/iick starch mucilage, place some in test-tubes
labelled A and B. Keep A for comparison, and to B add saliva,
and expose both to 40^ C. A is unaffected, while B soon becomes
fluid — within two minutes — and loses its opalescence ; this liquefac-
tion is a process qi;ite antecedent to the saccharifying process
which follows.

4. Stages between Starch and Maltose. — Mix starch and saliva
as in 3 (a.) C, and place in a water-bath at 40° C. At intervals of a
minute test small portions with iodine. Do this by taking out a
drop of the liquid by means of a glass rod. Place the drop on a
white porcelain plate, and with another glass rod add a drop of
iodine solution.

Note the following stages : — At first there is pure blue with
iodine due to the soluble starch formed giving also a Ijlue with
iodine, later a deep violet, showing the presence of erythro-dextrin,
the violet resulting from a mixture of the red produced by the
dextrin and the blue of the starch. Then the blue reaction entirely
disappears, and a reddish-brown colour, due to erythro-dextrin
alone, is obtained. After this the reaction becomes yellowish-
brown, and finally there is no reaction with iodine at all, aclii'OO-
dextrin being formed, along with a reducing sugar or maltose.
The latter goes on forming after iodine has ceased to react with the
fluid, and its presence is easily ascertained by Fehling's solution.
The soluble starch is precipitated by alcohol, while maltose is
not. In this way this body may be separated.

5. Effect of Different Conditions on Salivary Digestion.

(t. ) Label three test-tubes A, B, and C. Into A place .some saliva, boil it,
and add some starch mucilage. In B and C place starcli mucilage and saliva,
to B add a few drops of hydrochloric acid, and to C caustic potasli. Place
all three in a water-bath at 40 (J., and after a time test them for sugar by
Fehling's solution. No sugar is formed — in A because the ferment was de-

76 PRACTICAL PHYSIOLOGY. [VIIL

stroyed by boiling, and in B and C because strong acids and alkalies arrest
the action of ptyalin on starch.

(b.) If a test-tube containing starch mucilage and saliva be ])rej)ared as in
3 («.) C, and placed in a freezing mixture, the conversion of starch into a re-
ducing sugar is arrested ; but the ferment is not destroyed, for on ])lacingthe
test-tube in a water-bath at 40° C, the conversion is rapidly effected.

(f.) Mix raw starch with saliva and keep it at 40" C. Test it after half an
hour, when little or no sugar will be found.

6. Starch is a Colloid, but Sugar is a Crystalloid and dialyses.

(rt.) Place in a sausage parchment tube (p. 78), 20 cc. of starch mucilage (A),
and into anothei-, some starch mucilage with saliva (B). Suspend A and B
in distilled water in separate vessels.

(b.) After some hours test the diffusate in the distilled water. No starch
will be found in the diffusate of either A or B, but sugar will be found in that
of B, proving that sugar dialyses, while starch does not. Hence the necessity
of starch being converted into a readily diffusible body during digestion.

7. Action of Malt-Extract on Starch.

(a.) Rub u]) 10 grams of starch with 30 cc. of distilled water in a mortar,
add 200 cc. of boiling water, and make a strong starch mucilage.

(b. ) Powder 5 grams of pale loic-dncd malt, and extract it at 50° C. for half
an hour with 30 cc. of distilled water, and filter. Keep the filtrate.

('■. ) Place the starch paste of («. ) in a flask, and cool to 60" C. , add the ex-
tract of (i*). ), and place the Ha.sk in a water-bath at 60' C.

('/. ) Observe that the paste soon becomes fluid, owing to the formation of
soluble starch, and if it be tested from time to time (as directed in 4), it gives
successively the tests for starch and erythro-dextrin. Continue to digest it
until no colour is obtained with iodine — i.e., until all starch and erythro-
dextrin have disajipeared.

(c.) Take a portion oi [d.) and precipitate it with alcohol = achroo-dextrin.
The liquid also contains maltose (/. ).

(./.) Boil the remainder of the fluid, cool, filter, and evaporate the filtrate to
20 cc. Add 6 volumes of 90 per cent, spirit to pi'ecipitate the dextrin ; boil,
filter, and concentrate to dryness on a water-bath and dissolve the residue in
distilled water. The solution is maltose (Ci.^HkjO,, -t H^O) If the alcoholic
solution be exposed to air, crystals of maltose are formed.

ADDITIOXAL EXERCISES.

8. Gomnare the Eeducing Power of Maltose and Dextrose.

{(I.) With Fehling's solution estimate the reducing power of the solution
obtained in 7 ( /; ). (See " Urine.")

('/. ) Boil in a I'ask for half an hour 50 cc. of the solution of maltose with
5 cc. of hydrochloric acid. Neutralise with caustic soda, and make up the
volume, which has been reduced by the boiling, to 50 cc, and <leterminc by
Fehling's solution the reducing power. The acid has converted the maltose
into dextrose, and the ratio of the former estimation (<(.) tj the present one
should be (15 to 100.

(<•. ) A solution of pure dextrose treated as in ('/. )is not affected in its re-
ducing power.

Saliva lias practically the same effect on starch as malt-extract, and may be
used instead of the latter.

.X.]

GASTEiC DIGESTION. /t

9. Tetra-Paper, and Oxidising Power of Fluids, e.g , Saliva.— The papers
known as tetia-paper are used to estimate the oxidising power of a fluid, such
as saliva. They are impregnated with tetra-methyl-paraplienylene-diamine.
Tliis body, with i atom of oxygen assumes a violet tint, and a larger number
of atoms of oxygen enfeebles or discharges the colour so produced. C Wurster
has made tliis the ba«is for the measurement of the o.xidising jiower of tiuids,
the ozone of the air, or nitrous acid. Seven times as much oxygen is required
to destroy the colour formed as is necessary to form it from the original tetra-
base. The shades of colour in the empirical scale, which is suj)i)lied with the
tctra-jiajiers. are obtained by means of a .-olution of iodine. A certain depth
of tint on tlie scale corresjjonds to a certain amount of active oxygen (ozone)
I)er litre of the fluid. The papers and scale are supplied by Dr. Theodor
Scliuchardt. G. rlitz.

(".) Fold the paper and jJace it on a white porcelain background. If the
fluid to be tested is alkaline, moisten the paper previously with a drop of pure
glacial acetic acid, and allow a few drops of the fluid, e ;>., saliva, to run on
the paper. Compare the colour of the jjaper with the Roman numbers on the
scale ; this indicates the amount of ozone per litre. If the process be done in
a test-tube, the tetra-substance is dissolved out and the fluid becomes bluish.

LESSON IX.
GASTRIC DIGESTION.

1. Preparation of Artificial Gastric Juice.

(a.) Take part of the cardiac end of the pig's stomach, which has
been previously opened and washed rapidly in cold Avater, and
spread it, mucous surface upAvards, on the convex surface of an
inverted capsule. Scrape the mucous surface firmly with the
handle of a scalpel, and rub up the scrapings in a mortar Avith fine
sand. Add water, and rub up the Avhole vigorously for some time,
and filter. The filtrate is an artificial gastric juice.

(f).) V. Wittich's Method. — From the cardiac end of a pig's
stomach detach the mucous membrane in shreds, dry them lietween
folds of blotting-paper, place them in a bottle, and cover them Avith
strong glycerine for several days. The glycerine dissolves the
pepsin, and on filtering, a glycerine extract Avith high digestive
properties is obtained.

(r.) Kiihne's Method. — Take 130 grams of the cardiac mucous membrane
of a jiig's stomach, and place it in 5 litres of water containing 80 cc. of 25 per
cent, hydrochloric acid {i.e., .2 ])er cent.). Heat the whole for twelve hours at
40' C. Almost all the mucous membrane is dissolved. Strain through flannel
and tlien filter. This is a powerfully peptic fluid, but it contains a small
quantity of peptones It can be kept for a long time. The test of an active
]ireparation of gastric juice is that a tliread of fibrin, when placed in the fluid
and warmed, should be dissolved in a few minutes.

72

PRACTICAL PHYSIOLOGY.

[IX.

(c/.) Instead of (a.) or (/;.) use Benger's liquor pepticus, or the
pepsin of Burroughs, Wellcome, & Co., or that of Park, Davies,
& Co.

All the above artificial juices, when added to hydrochloric acid
of the proper strength, have high digestive powers.

2. Pepsin and Acid (HCl) are necessary for Gastric Diges-
tion.

(«.) Take three beakers or large test-tubes, label them A, B, C.
Put into A water and a few drops of glycerin extract of pepsin or
powdered pepsin. Fill B two-thirds full of hydrochloric acid 0.2
per cent., and fill C two-thirds full with 0.2 per cent, of hydrochloric
acid, and a few drops of glycerin extract of pepsin. Put into all
three a small quantity of well-washed fibrin, and place them all in
a water-bath at 40' C. for half an hour.

(/>.) Examine them. In A, the fibrin is unchanged ; in B, the
fibrin is clear and swollen up ; in C, it has disappeared, having
first become swollen up and clear, and completely dissolved, being
finally converted into peptones. Therefore, both acid and ferment
are required for gastric digestion.

The results obtained, all the tubes being at 40° C, are : —

Tube a.

Tube B.

Tube C.

Water.
Pepsin.
Fibrin.

Water.

Hydrochloric acid.
Fibrin.

Water.
Pepsin.

Hydrocliloric acid.
Fibrin.

Afteii Twenty Minutes.

1

Uncliajiged.

Fibrin begins to swell up
becomes clear, and
small quantity of acid
albumin formed.

Acid albumin formed
(precipitated on neu-
tralisation) albumoses
formed (i)recii)itated by
(NHJ SO4), and small 1
quantity of peptones.

1

After One Hour.

1

Unchanged.

More acid-albumin
formed.

Small amount (or no)
acid - albumin ; albu-
moses, and much
peptone.

IX.]

GASTRIC DIGESTION.

73

3. Hydrochloric Acid of 0-2 per cent,— Add 6.5 cc. of ordinary com-
mercial hydrochloric acid to i litre of distilled water.

4. Products of Peptic Digestion and its Conditions.

(a.) Half fill three large test-tubes, labelled A, B, C,

with

Fig. 42.— Digestion-Bath.

hydrocliloric acid 0.2 per cent. Add to each five drops of glycerin
extract of pepsin. Boil B, and
make C faintly alkaline with
sodic carbonate. The alkalinity
may be noted by adding pre-
viously some neutral litmus
solution. Add to each an equal
amount — a few threads of well-
washiid fibrin — which has been
previously steeped for some time
in 0.2 per cent, hydrochloric
acid, so that it is swollen up
and transparent. Keep the
tubes in a water-bath (fig. 42)
at 40° C. for an hour, and ex-
amine them at intervals of
twenty minutes.

(b.) After five to ten minutes,
or less, the fibrin in A is dissolved, and the fluid begins to be
turbid. In B and C there is no change. Even after long exposure
to 40° C. there is no change in B and C. After three-quarters of
an hour filter A and part of B and C. Keep the filtrates.

(r.) Carefully neutralise the filtrate of A with dilute caustic
soda = a precipitate of acid-albumin. Filter off this precipitate,
dissolve it in 0.2 per cent, hydrochloric acid. It gives proteid
reactions (Lesson I. 7).

('/.) Test the filtrate of ('*.) for aWumo-^e or proteose. Repeat
all the tests for albumose (I.esson I. 10). Albumose is soluble in
water, and gives all the ordinary proteid reactions. It is precipi-
tated by nitric acid in the cold in presence of NaCl, but the
precipitate is redissolved with the aid of heat, and reappears on
cooling. This is a characteristic reaction. It is precipitated by
acetic acid and ferrocyanide of potassium ; by acetic acid and a
saturated solution of sodic sulphate ; and by metaphosphoric acid :
while peptones are not. It gives the biuret reaction (like peptone).
Like peptones, it is soluble in water.

(e.) To part of the filtrate of ('•.) add neutral ammonium sul-
phate to saturation. This precipitates all the albumoses, while
the peptones are not precipitated, but remain in solution. Filter
and test the filtrate for peptones (Lesson I. 10). In the biuret

74

PRACTICAL PHYSIOLOGY.

[IX.

reaction owing to the presence of (NH4)2SOj a great excess of soda
lias to be added.

(/.) Neutralise part of the filtrates of B and C. They give no
precipitate, nor do they give the reactions for peptones. In B the
ferment pepsin was destroyed by boiling, while in C the ferment
cannot act in an alkaline medium.

{g.) If to tbe remainder of C acid be added, and it be placed
again at 40° C, digestion takes place, so that neutraUsation has not
destroyed the activity of the ferment.

Instead of fibrin white of egg may be used.

The methods used by Kiihne to isolate the varieties of albumose
are purposely omitted here (p. 78).

Prodiids of Gastric Digestion.

To 50 grams well-washed and boiled fibrin + 250 cc. 0.2 per cent.
HCl. Digest for twenty -four hours at 40° C. Neutralise with sodium
carbonate.

Precipitate = Acid-
albumin.

Filtrate : Albumose -f Peptone.
Saturate with (NH4).S0j.

Precipitate = AJhiimoscs.

Boil witli Barium Carbonate.

Filtrate : Peptone + (NH4)^S04.
Boil with Barium Carbonate.

II II

i I I.I

Residue of Yi\ivAie = Alhumose- Residue of ¥\\t\'a,iQ = Pei ■to iic-

ttarium Sulphate, solution whicli can Barium Sulphate, solution containing

be precipitated by Baryta. Precipitate

alcohol. pe})tone by alcohol.

5. Tests for Albumose (Lesson I. 10). — It is precipitated by
the following substances : Xitric acid ; acetic acid and NaCl ; acetic
acid and ferrocyanide of potassium. The precipitates are soluble
on heating and reappear on cooling. In all these respects it
differs from peptone. Like pei)tone, however, it gives the biuret
reaction, and is not coagulated by heat.

6. Test for Peptones (Lesson I. 10, VI.).

The following table from Halliburton shows at a glance the chief

IX.]

GASTRIC DIGESTION.

75

characters of the final product peptone, and the intermediate
albumoses in contrast with those of a native proteid Hke albumin.

Variety of
Proteid.

Action of
Heat.

Action of
Alcohol.

Action of
Nitric acid.

Action of
(NH4).jS04.

Action of
NaU0-(-CuS04.

Diffusi-
bility.

Albumin.

Coagu-
lated.

I Then coagu-
lated.

i In cold, not
readily
solul)le on
heating.

Precipitated.

Violet colour.

Nil.

Proteoses
(^AIbui)ioses).

Not coagu-
lated.

I But not
coagulated.

^ In cold,
soluble on
heating, re-
appearing
on cooling.

Precipitated.

Rose-red
colour
(biuret re-
action).

Slight.

Peptones.

Not coagu-
lated.

I But not
coagulated.

Not pre-
cipitated.

Not precipi-
tated.

Rose-red
colour
(biuret re-
action).

Great.

(The ^ indicates precipitated.)

7. Action of Gastric Juice on Milk.

(a.) Mix 5 cc. of fresh milk in a test-tube with a few drops of
neutral artificial gastric juice ; keep at 40^ C. In a .short time the
milk curdles, so that the tube can be inverted without the curd
falling out. Ey-and-by whey is squeezed out of the clot. The
curdling of milk by the rennet ferment present in the gastric juice
is quite difterent from that produced by the "souring of milk,"
or by the precipitation of caseinogen by acids. Here the casein
(carrying with it most of the fats) is precipitated in a neutral fluid.

{h.) To the test-tube add 5 cc. of 0.4 per cent, hydrochloric acid,
and keep at 40° C. for two hours. The pepsin in the presence of
tlie acid digests the casein, gradually dissolving it, forming a
straw-yellow-coloured fluid containing peptones. The " peptonised
milk " has a peculiar odour and bitter taste.

(c.) Peptonised Milk. — To 5 cc. of milk in a test-tube add a
few drops of Bengcr's liquor pepticus, and place in a water-bath.
Observe how the caseinogen first clots, and is then partially dissolved
to form a yellowish-coloured fluid, with a bitter taste and peculiar
odour. There generally remains a very considerable clot of casein ;
and, in fact, the gastric digestion of milk is slow, especially if com-
pared with its tryptic digestion (Lesson X. 11). Test the fluid for
peptones with the biuret reaction, and observe the light-pink colour
obtained. The bitter taste renders milk " peptonised " by gastric
juice unsuitable for feeding purposes.

8. Action of Rennet on Milk. — (Rennin the enzyme.)

(a.) Place milk in a test-tube, add a drop or two of rennet, and

^6 PRACTICAL PHYSIOLOOT. [iX.

place the tube in a water-bath at 40° C. Clark's commercial rennet
will do. Rennet is obtained from the fourth stomach of the calf.
The milk becomes solid in a few minutes, forming a curd, and
by-and-by the curd of casein contracts and squeezes out a fluid —
the whey.

(6.) Repeat the experiment, but previously boil the rennet. No
such result is obtained as in (a.), because the rennet ferment or
rennin is destroyed by heat.

9. Comparison of Mineral and Organic Acids.

(a.) Take two test-tubes A and B. Place in A 10 cc. of a 0.2
per cent, solution of hydrochloric acid, and in B 10 cc. of a 2 per
cent, solution of acetic acid. To both add a few drops of
oo-Tropseolin dissolved in alcohol. The very dilute mineral acid
in A renders it rose-pink, while the organic acid does not affect its
colour. Or, what is perhaps a better method, allow a drop of a
saturated alcoholic solution to evaporate on a white porcelain slab at
40° C, and while at this temperature add a drop of the acid solution.
On evaporation a violet tint indicates an inorganic acid, .005 HCl
can be thus detected {Langlcy). It is stated not to be quite a
reliable test in the presence of certain organic matters.

{^.) Repeat (^^), but add to the acids a dilute watery solution of
methyl-violet, and note the change of colour produced by the
mineral acid. It becomes blue and then green. If a strong solution of
acid be used, the colour is discharged, but this is never the case
with the percentage of acid in the stomach. The peptones in
gastric juice may be precipitated by the previous addition of 10 per
cent, tannic acid, and then the test can be applied. In the presence
of proteids in gastric juice it does not give absolutely reliable results.

('•.) Repeat (a.) with the same acids, but use paper stained with
congo-red, and observe the change of colour to blackish-blue or
intense blue produced by the hydrochloric acid. AVash in ether ;
if the red colour reappears the acid is organic, if not, mineral.
Organic acids make it violet, not blue.

{(l.) Phloro-Glucin and Vanillin ((?«>(,j&w7). — Dissolve 2 grams of phloro-
ghicin and i gram of vanillin in 100 cc. alcohol. Mix equal quantities of this
with the fluid to be testad, and evaporate the mixture in a watch-glass on a
water-bath. Do not allow the fluid to boil. The presence of HCl is shown
by the formation of a delicate rose-red tinge or stain, or, if there be much
hydrochloric acid, of red crystals. This reaction will detect .06 per cent.
Ho'l, and is said not to be impeded by organic acids, albumin, or peptone.
The test is an expensive one.

(c.) Benzo-PuTDurin 6 B. — Use blotting-papers soaked in a saturated watery
solution of this fluid and dried. HCl (.4 grm. in 100 cc. ) makes them dark
blue, wliile organic acids make them brownish -violet. If both HCl and
organic acids be present, the stain is brownish black ; but if the stain be
suspected to be partly due to HCl, wash the paper in a test-tube with
sulphuric ether, which removes the stain due to the organic acid, leaving that

[X.] GASTRIC DIGESTION. 'JJ

due to the HCl unaffected. The sulphuric ether does not affect the mineral
acid stain.

( f.) Mohr's Test. — Mix together 2 cc. of a 10 per cent, solution of sulpho-
cyanide of potassium. 0.5 cc. of .a neutral solution of ferric acetate, and 8.5 cc.
water. Place a few drops of this ruby-red fluid on a porcelain capsule, and
allow a few diops of the gastric juice to mix with it = a light violet colour at
the point of contact, and a mahogany brown when the fluids mix. It is less
sensitive than the aniline tests.

((/. ) Shake up a mixture of dilute HCl and an organic acid, e.g., lactic, with
ether. Remove the ether, and on evaporating it, it will be found to have
dissolved the organic acid, but not the mineral one. On this fact is based
Richet's method of determining the amount of an organic acid in presence of
a mineral acid.

These reactions for a mineral acid are specially to be noted, as
they are used clinically for ascertaining the presence or absence of
hydrochloric acid, e.g., in a vomit. This acid is frequently absent
from the gastric juice in cancer of the stomach. In gastric catarrh
the HCl may be greatly diminished and lactic acid abundant. The
presence of peptones interferes with the dehcacy of some of these re-
actions. The reactions (c), (c/.), (e.), are the most to be depended on.

10. Carbolo-Chloride of Iron Test for Lactic Acid {Uffehna'tm).—Y\^^a.x^
a fresh solution by mixing 10 cc. of a 4 per cent, solution of carbolic acid with
20 cc. of distilled water, and i drop of liquor ferri perchloridi. The
amethyst-blue solution thus obtained is changed to ydlow by lactic acid, while
it is not atlected by 0.2 per cent. HCl ; but alcohol, sugar, and phosphate,
yield a similar reaction.

A faintly yellow coloured solution of ferric chloride (2-5 drops to 50 cc. water)
is not affected by the addition of HCl, acetic, or butyric acid, but it is inten-
sified in the presence of dilute lactic acid.

ADDITION"AL EXEECISES.

[Proteids, e.q., albumin, are split up by certain acids and ferments, as
shown by Kiihne, into an anti-group and a hemi-group. In the case of
ferments, the following scheme represents the results : —

Action of Enzymes (Ferments).
, Albumin.

(U to

o ■"o

Anti-albumose. Hemialbumose.

Anti-pe})toue. Anti-peptone. Hemi-])eptone. Hemi-peptone.
Ampho-peptone.

i-'^

Leucin, Tyrosin, Leucin, Tyrosin,
&c. &c.

7^

PRACTICAL PHYSIOLOGY.

[IX.

The anti-group is not farther split up, but the hemi-group, although not
split up by peptic digestion, is split up by tryptic digestion into leucin,
tyrosin, and other jiroducts.

The substance hitherto called hemi-albumose has been shown by Kiihne
to consist of three albunioses, viz., proto-albumose, hetero-albumose, and
deutero-albumose. The first two are precipitated by NaCl, and the last by
NaCl and acetic acid. For separation of these bodies — which can be obtained
most easily from Witte's peptone — see 13,

11. To Prepare Albumose and Gastric Peptones in Quantity.

(o.) Place lo grams of fresh, well-washed, expressed fibrin in a porcelain
capsule, cover it with 300 cc. of 0.2 per cent, hydrochloric acid, and keep the
whole at 40° C. in a water-bath until the whole of
the fibrin is so swollen up as to become converted
into a perfectly clear, jelly-like mass, and it becomes
so thick that a glass rod is supjiorted erect in it.

(6.) Add I or 2 cc. of glycerin pepsin extract or
the artificial gastric juice, 1 {c), and stir the mass.
"Within a few minutes the whole becomes fluid.

(c.) After a short time — fifteen to twenty minutes
— before the peptonisation is complete, filter and
exactly neutralise the filtrate with amitionia or
caustic soda, which precipitates the acid albumin
with a small quantity of the albunioses. Filter ;
the filtrate contains the albumoses, which can be
precipitated by saturation with crystals of neutral
ammonium sulphate. To get rid of this salt the
precipitate must be dialysed in a Kiihne's dialyser
(fig- 43)-]

12. Comparative Digestive Power of Pepsins,

e.g., the various ])epsins found in the market, or
the com})arative digestive power of glycerine ex-
tracts of the stomach. Chop up well-washed and
boiled fibrin, and stain it with ammoniacal carmine
(24 hours). Wash thorouglily and ])reserve under
ether. Place in the requisite number of beakers

vr^ r-:;?, '„ t.- i -2 per ceut. HCL, equal amounts of the carmine

Fig. 43. — Kunnes Dialyser. ^. k j 4.1 jj 4.1 • 1 4. j.-i

A parchment tube, such as norm, and then add the pepsin whose strength

is used for sausages, is sus- is to be tested; keep at 40' C. As the fibrin is

pendedni a vessel tlirough digested the carmine is set free, so that the most

tin uaily ^flowing ^^ ''°"' deeply-stained liquid contains the most active

pepsin {Gratzner''s Method).

13. Albumoses. — Dissolve Witte's peptone in 10 per cent, sodium chloride
solution and filter. This solution does not coagulate on heating, but gives
the ordinary proteid reactions, together with biuret and nitric acid tests
(Lesson I.).

{a.) Saturate the solution with (NHJoSO^ = precipitate of albumoses.
Filter. The peptone is in the filtrate and can be precipitated by alcohol.

{b.) Dialyse anotlier portion of the solution; lictera-albumose is precipitated.

(c. ) Faintly acidify another ])ortion of the solution, and then saturate it
with sodium chloride = precipitate of proto-albumose and hetero-albumose.
Filter. The filtrate contains the deutero-albumose and peptone. Precipitate
the deutero-albumose by saturating with ammonium sulphate.

X.] PANCREATIC DIGESTION. 79

14. Chemical Examination of the Gastric Contents, e.g., Vomit.

{a.) Test the reaction.

[b.) Determine the acidity {e.q., of lo cc.) by means of a deci-normal solution
of caustic soda. (See " Urine.")

(c.) Test lo cc. for the presence of pepsin (digest with fibrin and HCl), and
rennet (milk).

(rf.) Use the tests 9 (c), [d.), [e.), for determining the presence of free
HCl.

(e. ) Make a rough estimate of the presence of lactic, butyric, and acetic acids
by the method 9 ((/.).

(/.) Examine for proteids, r.q., albumin, albumoses, and peptone.

{g. ) Test for sugar and its digestive products.

(A.) Distil some of the fluid, extract the remainder with sulphuric ether, and
in the latter estimate the lactic acid which it contains.

(i.) Test Meal. — When it is desired to know if digestion is normal a
test-meal is given. Ewald recommends a roll of stale bread taken on an
empty stomach, with tea or water. After an hour the contents of the stomacli
are pumped out by means of a stomach pump, and examined as above.

LESSON X.

PANCREATIC DIGESTION.

1. Preparation of Artificial Pancreatic Juice.

[it.) Mince a portion of the pancreas of an ox twenty-four hours
after death, rub it up with well-washed fine sand in a mortar, and
digest it with cold water, stirring vigorously. After a time strain
through muslin, and then filter through paper. The filtrate has
digestive properties, chiefly upon starch. Instead of water, a more
potent solution is obtained by digesting the pancreas at 40° C. for
some hours with a 2 per cent, solution of sodic carbonate. To pre-
vent the putrefactive changes which are so apt to occur in all
pancreatic fluids, add a little 10 per cent, alcoholic solution of
thymol.

{b.) Make a glycerin extract of the pancreas (pig) in the same
way as described for the stomach (Lesson IX. 1, V). Before
putting it in glycerin, it may be placed for two days in absolute
alcohol to remove all the water. The glycerin extract acts on
starch and proteids.

8o PRACTICAL PHYSIOLOGY. [X.

{('.) For most experiments use the " liquor pancreaticus " of
Benger, or of Savory & Moore, or Burroughs, Wellcome & Co.

{d.) Weigh the pancreas taken from a pig just killed, rub it up with sand in
a mortar, and add i cc. of a i per cent, solution of acetic acid for every gram
of pancreas. Mix thoroughly, and after a quarter of an hour add lo cc. of
glycerin for every gram of pancreas. After five days filter off the glycerin
extract. The acetic acid is added to convert the unconverted "zymogen"
into trypsin.

(e.) Kiihne's Dry Pancreas Powder. — This is obtained by thoroughly
extracting a pancreas with alcohol and ether, and drying the residue. The
extraction must be done in an ether fat-extracting apparatus; and as the
process is somewhat tedious, it is better to buy the substance. It can be
obtained from Dr. Griibler of Leipzig. Extract the dry pancreas powder with
five ])arts of a .2 per cent, solution of salicylic acid, and keep it at about 40° C.
for eight or ten hours. Use 20 grams of the dry pancreas to 100 cc. of
salicylic acid fluid. Strain it through muslin, and press out all the fluid
from the residue. The hands must be well washed, as pancreatic digests are
so liable to undergo putrefaction. It is well to cover the vessel with paper
moistened with an alcoholic solution of thymol. A dense, tough, elastic
residue is obtained. Re extract the latter for several hours at 90" C. with
sodic carbonate solution (.25 per cent.), adding a few drops of alcoholic solu-
tion of thymol, f ilter the first extract and allow it to stand. Very probably
a large mass of crystals of tyrosin will separate. Filter off the deposit and
mix the salicylic and alkaline extracts. The extract has only proteolytic pro-
perties. I find this extract acts much more energetically than those prepared
in other ways. What remains after the action of salicylic acid and sodic car-
bonate contains leucin and tyiosin.

(/.) Solution of Pancreatic Enzymes. — Apart from the fat-splitting ferment
or enzyme, the other ferments are readily extracted from tlie gland — under
certain conditions by (i.) glycerin, (ii. ) saturated watery solution of chloro-
form (Roberts), but the chloroform extract interferes with the reaction for
grape-sugar. Harris and Gow find that a saturated solution of common salt
extracts all the pancreatic enzymes (save the fat-splitting). Roberts found
that by extracting the pancreas with a solution containing a mixture of
boracic acid and borax a serviceable extract was obtained.

2. I. Action on Starch (Amylopsin the ferment),
{a.) To thick starch mucilage in a test-tuhe add glycerin extract
of pancreas or liquor pancreaticus, and place it in a water bath at
40° C. Eapidly the starch paste becomes fluid, loses its opal-
escence, and becomes clear. Within a few minutes some of the
starch is converted through intermediate stages (p. 69) into
maltose. Test for sugar (Lesson III. 8, V.).

(6.) Pancreatic Juice and Bile. — Repeat A, but add a little bile,
the starch disappears more quickly. Prove by testing on a white
porcelain slab, as in Lesson VIII. 4.

8, The same conditions obtain as for saliva (Lesson YTII. 6).

X.] PANCREATIC DIGESTION. 8.1

4. II. Proteolytic Action and its Conditions (Trypsin the fer-
ment),

(a.) Half-fill three test-tubes A, B, C, with i per cent, solution
of sodium carbonate, and add 5 drops of glycerin pancreatic extract
or liquor pancreaticus in each. Boil B, and make C acid with dilute
hydrochloric acid. Place in each tube an equal amount of well-
washed fibrin, plug the tubes with cotton-wool, and place all in a
water-bath at 40° C.

(/».) Examine them from time to time. At the end of one, two,
or three hours there is no change in B and C, Avhile in A the fibrin
is gradually being eroded, and finally disappears, but it does not
swell up, the solution at the same time becoming slightly turbid.
After three hours, still no change is observable in B and C.

(c.) Filter A, and carefully neutralise the filtrate with very
dilute hydrochloric or acetic acid = a precipitate of alkali-albiimin.
Filter off the precipitate, and on testing the filtrate, peptones are
found. The intermediate bodies, the albumoses, are not nearly so
readily obtained from pancreatic as from gastric digests.

(d.) Filter B and C, and carefully neutralise the filtrates. They
give no precipitate. No peptones are found.

{e. ) Test the proteolytic power of an extract of Kiihne's " pancreas powder "
(Lesson X., I, e). For this purpose the salicylic and alkaline extracts are
mixed with well-washed fibrin and digested at 40° C. for ten hours or longer.
The vessel is covered with thymolised paper. Strain through linen and
then filter. Test the digest for jjeptones. It is difficult to get any albumoses
after this time ; the anti-albumoses are already converted into anti-j)eptones,
the hemi-albumose into hemi-peptone, and some of the latter is decomposed
into leucin and tyrosin.

As putrefaction takes place w'ith great rapidity in pancreatic
digests, it is essential to prevent this either by the addition of an
alcoholic solution of thymol or chloroform water (5 cc. chloroform
to I Utre water). To get satisfactory results it is better to do it on
a somewhat larger scale {>Salkowsk/).

Tryptic Digestion.

50 grams fibrin + 200 cc. alkaline (carbonate of soda i per cent.) chloroform
water + liq. pancreaticus digested for 36 hours ; then boil and filter.

I I

Residue ; coagulated Filtrate (A) (reaction with bromine)

Proteid. concentrated by evaporation

and allowed to stand.

I

I I

Deposition (B) of Filtrate (C) further

Tyrosin. concentrated ; Leucin

and Peptone.
F

82 PRACTICAL PHYSIOLOGY. [X.

5, Products other than Peptones. — Leucin (CgHigNOg) and
Tyrosin (C9H11NO3).

(a.) Place 300 cc. of a i per cent, solution of sodic carbonate in
a flask, add 5 grams of fibrin, 5 cc. of glycerine extract of pancreas,
and a few drops of an alcoholic solution of thymol. Keep all at
38° C. on a water-bath for ten to sixteen hours, shaking frequently.
After sixteen hours take a portion of the mixture, filter, and to the
filtrate cautiously add dilute acetic acid to precipitate any alkali-
albumin that may be present in it. Filter, and evaporate the
filtrate to a small bulk, and precipitate the peptones by a consider-
able volume of alcohol. Filter to remove the peptones, and eva-
porate the alcoholic filtrate to a small bulk, and set it aside, when
tyrosin and leucin separate out. Keep them for microscopic examin-
ation (figs. 44, 79).

(h.) A much better method of obtaining leucin and tyrosin is to
digest, at 40° C, for twenty-four to thirty-six hours, equal parts of
fresh moist fibrin and ox-pancreas in i htre of i per cent, sodium
carbonate solution to which some thymol has been added, or, an
ox-pancreas is digested in the same way, the white of an egg being
added every ten hours (Digest A). Make another digest; but
do not add thymol. Digestion and putrefaction take place, the
latter causing a most disagrpeable smell (Digest B). Filter the
digest A, and to some of it add j\Iillon's reagent, which precipitates
any albumin. Filter, boil the filtrate, a red colour indicates tyrosin.

Concentrate some of tlie filtered digest A by boiling it to a small
bulk on a water-bath. After several hours examine a drop micro-
scopically for leucin and tyrosin. Precipitate the peptones in some
of the filtered digest A by alcohol. Filter. Concentrate the filtrate
on a water-bath, Avhen a sticky deposit of leuc'n is formed.

The digest A yields the chlorine or " bromine reaction."

The digest B is to be used for testing for the products of putre-
faction.

(c.) Examine the crystals of leucin and tyrosin microscopically
(figs. 44, 79). The former occurs as brown balls, often with
radiating lines, not unlike fat, but much less refractive, and the
latter consists of long Avhite shining needles arranged in sheaves
or in a stellate manner, or somewhat felted. (See " Urine.")

(d.) Test for Tyrosin (Hofmann). — Dissolve some crystals by
boiling them in water, add Millon's reagent, and boil, which gives
a red colour. The deposit which is sometimes formed in Benger's
liquor pancreaticus consists of tyrosin.

(e. ) Test a solution of tyrosin, obtained by the prolonged boiling of horn
shavings and sulphuric acid, with Millon's reagent as in (rf.).

X.] PANCREATIC DIGESTION. 83

6. Putrefactive Products of Pancreatic Digestion. — These include indol,
skatol, phenol, volatile fatty acids, CO.,, H^S, CH4, and H.

,CH = CH
Indol CeHZ ^-^—-' = CsH^N and

/C.CH3 = CH
Skatol CgH/ ___ =C9H9N.

Indol is one of the many putrefactive products of the decomposition of pro-
teids. Take equal parts of fresh fibrin and finely-divided ox-pancreas, add
ten times the volume of water, and keej) the whole continuously at a tempera-
ture of 40° C. for three or four days. Intensely disagreeable-smelling gases
are given off. Strain through linen, acidulate (acetic acid), and distil the
filtrate. The filtered distillate is made alkaline by KHO or NaHO, and
shaken thoroughly with its own volume of ether. Distil the'ether, and the oily
substance which remains behind, on being di.ssolved in water, is allowed to
crystallise. The solution yields the following tests.

Tests for Indol. — Use either tlie watery solution of indol or the
filtered offensive-smelling fluid before it is distilled.

(a.) Warm the liquid, and add first a drop or two of dilute
sulphuric acid to some of the filtered liquid, and then a very dilute
nitrite solution. A red colour indicates the presence of indol. This
test is very readily obtained with the products of digestion by
KiJhne's dry pancreas (Lesson X. 1, e). One must be careful to
regulate the strength of the acid, as too strong nitrous acid prevents
the reaction.

(6.) Acidify strongly with hydrochloric acid a small quantity of the highly
offensive fluid or the watery solution, and place in it a shaving of wood or a
wooden match with its head removed and soaked in strong hvdroihloric acid.
The match is coloured red, sometimes even an intense red. The match can be
dried, and it keeps its colour for a long time, although the colour darkens
and becomes somewhat duskier on drying.

(c.) Chlorine Reaction. — Add to some of the digestive fluid (5,
h, preferably digest B), drop by drop, chlorine water ; it strikes
a rosy-red tint. Or add very dilute bromine water (i to 2 drops
to 60 cc. water), tlie fluid first becomes pale red, then violet, and
ultimately deep violet (Kiihne).

7. III. The Action on Fats is Twofold.
(A.) Emulsification.

(o.) Rub up in a mortar which has been warmed in warm water
a little olive-oil or melted lard, and some pieces of fresh pancreas.
A creamy persistent emulsion is formed. Examine the emulsion
under the microscope. Or use a watery extract of the fresh pan-
creas, and do likewise ; but in this case the result will not be nearly
so satisfactory.

84 PRACTICAL PHYSIOLOGY. [X.

(h.) Rub up oil as in («.) ; but this time use an extract of the fresh pancreas
made with i per cent, sodic carbonate. A very perfect emulsion is obtained,
even if tlie sodic carbonate extract is boiled beforehand. This shows that its
emulsifying power does not depend on a ferment.

(c. ) The i)resence of a little free falty acid greatly favours emulsification.
Take two samples of cod-liver oil, one pcrfcdly neutral (by no means easily
procured), and an ordinary brown oil — e.g., De Jongh's. The latter contains
nuicli free fatty acid. Place 5 cc. of each in two test-tubes, and pour on them
a little solution of sodic carbonate (i per cent.). The neutral oil is not
emulsified, while the rancid one is at once, and remains so. Many oils that
do not taste rancid coi.tain free fatty acids, and only some of them give up
their acid to water, just according as the fatty acid is soluble or not in water.

8. (B.) The Fat-Splitting Action of Pancreatic Juice (Steapsin
or pialyn, the ferment).

{a.) Prepare a Perfectly Neutral Oil. —A perfectly ^c«<m/ oil is required,
and as all commercial oils contain free fatty acids, they must not be used.
Place olive or almond oil in a porcelain capsule, mix it with not too much
baryta solution, and boil for some time. Allow it to cool. The unsaponified
oil is extracted with ether, the ethereal extract separated fi'om the insoluble
portion, and the ether evaporated over warm water. The oil should now be
perfectly neutral {Krukcnbrrg).

{b.) Mix the oil with finely divided, perfectly fresh pancreas (not a watery
extract), and keep it at 40" C. After a time its reaction becomes acid, owing
to the formation of a fatty acid. This experiment is by no means easy to ]ier-
form, and some observers deny altogether the existence of a fat-splitting
ferment. Tlie free fatty acids thus liberated unite with the alkaline bases of
bile, and form soaps.

9. IV. Milk-Curdling Ferment.

(a.) Add a drop or two of the brine extract of the pancreas pre-
pared for you to 5 cc. of warm milk in a test-tube, and keep it at
40° C. AVithin a few minutes a solid coagulum forms, and there-
after the whey begins to separate.

{Ii.) Repeat (a.), but add a grain or less of bicarbonate of soda to
the milk. Coagulation occurs just as before, so that this ferment
is active in an alkaline medium.

(c.) Boil the ferment first. Its power is destroyed.

10. Action on Milk.

(a.) Place cow's milk diluted with 5 volumes of water in a test-
tube, add a drop or two of pancreatic extract or liquor pancrea-
ticus. Keep at 40° C. for half an hour. The caseinogen is first
curdled and then dissolved, and as this occurs, the milk changes
from a white to a yellowish colour.

(6.) Divide (a.) into two portions, A and B. To A add dilute
acetic acid ; there is no precipitation of caseinogen, which has been
converted into peptones. To B add caustic soda and dilute copper
sulphate, wliich give a rose colour, proving the presence of peptones.

X.] PANCREATIC DIGESTION. f?5

11. To Peptonise Milk, — A pint of milk is diluted with a
quarter of a pint of water, and heated to a lukewarm temperature,
about 140° F. (60° C). Or the diluted milk may be divided into
two equal portions, one of wliich may be heated to the boiling-
point and then added to the cold portion, the mixture will then be
of the required temperature. Two tea-spoonfuls of liquor pancrea-
ticus, together with about fifteen grains, or half a level tea-spoonful,
of bicarbonate of soda, are then mixed therewith. The mixture is
next poured into a jug, covered, and placed in a warm situation to
keep up the heat. In a few minutes a considerable change will
have taken place in the milk, but in most cases it is best to allow
the digestive process to go on for ten or twenty minutes. The
gradually increasing bitterness of the digested milk is unobjection-
able to many palates ; a few trials will, however, indicate the limit
most acceptable to the individual patient ; as soon as this point is
reached, the milk should be either used or boiled to prevent further
change. From ten minutes to half an hour is the time generally
found sufficient. It can then be used like ordinary milk.

ADDITIONAL EXERCISES,

. 12. Preparation of Indol. — Place i kilogram of fresh fibrin in a 6-litre jar
with 4 litres of water (to which i gram KH_,P04 and .5 gram MgS04 are
added). Mix this with 200 cc. cold saturated solution of sodic carbonate, and
add to the whole a quantity of putrefying flesh-juice and some pieces of the
putrid flesh as well. Cork the vessel, a vent-tube being placed in the cork,
and place it aside f^r 5-6 days at a temperature of 40-42° C. Distil and
acidify the strongly ammoniacal distillate with HCl, add some copper
sulphate, and filter. Shake up equal volumes of the distillate and ether in a
separation funnel. Allow the filtrate to settle, run it off", add some fresh
filtrate, and shake again with the same ether. Distil the ethereal extract to
about one- fourth of its volume, shake up the residue very thoroughly with
caustic soda (to remove phenol and traces of acids). Distil the ether, and
after the addition of caustic soda distil the oily indol. The distillate is shaken
up with ether, and the ethereal extract is evaporated at a low temperature,
when crystals or plates of indol separate. This preparation usually contains
some skatol. {JJrechsel after Salkowski.)

Some Nitrogenous Dkkivatives of the Foregoing.

13. Leucin or o-Amido-isobutylacetic acid, C6H|:jNO., = 2 CH3)CH— CH,—
CH(NH2)C0.0H, and Tyrosin or Paraoxyphenyl-a-Amidopropionic acid.

C^,iN03=C6H4<§^(NH2)CO. OH.— These two bodies are obtained

together from nearly all proteidswhen the latter are decomposed by the action
of acids. The former belongs to the fatty bodies, and tyrosin to the aromatic
group, and is a derivative of benzene (CgHg).

86

PRACTICAL PHYSIOLOGY.

[X.

Preparation of Leucin and Tyrosin.— Place 2 parts of horn shavings
(J-i kilo.) in a mixture of 5 parts of concentrated sulphuric acid and 13 parts
of water. Boil for twenty-four hours in a vessel placed in connection with a
condenser. Add thin milk of lime until a feebly alkaline reaction is obtained,
filter through flannel, re-extract the residue with water, mix the filtrate and
washings and slightly acidulate them with oxalic acid. Filter to remove the
oxalate of lime, and evaporate the filtrate until a scum forms on the surface.
Cool and repeat tlie evaporation process until crystallisation ceases to take

place in the mother-fluid. Collect the
mass of crystals, dissolve them in boiling
water with the addition of ammonia, and
add lead acetate until the I'esulting pre-
cipitate is no longer brown, but becomes
white. Filter, acidulate the acid filtrate
feebly with dilute sulphuric acid, filter off
the lead sulphate and allow the fluid to
cool, when tyrosin in an almost pure form
crystallises out.

The mother-liquor, freed from tyrosin, is
treated with sulphuretted hydrogen to get
rid of the lead, filtered, evaporated, and
boiled for a few minutes with freshly
precipitated hydrated copper oxide, which
si"- forms a dark blue solution. The latter,
when filtered and evaporated, yields blue
crystals and an insoluble compound of leucin-copper oxide. This deposit and
the crystals are decom])osed in water by H.S-solution, the filtrate when
necessary decolorised by boiling with animal charcoal, again filtered and
evaporated to crystallisation, wlien leucin crystallises out. It is obtained
[)ure by recrystallisation from boiling alcohol {Drcchscl).

Fio. 44. —Crystals and Sheaves of Tyii

14. Tyrosin is insoluble in alcohol and in 1000 parts of cold water.

(a. ) Observe microscopically its crystalline form, as fine long silky needles
arranged in sheaf-like bundles (fig. 44).

(.b.) Boil a hot watery solution with Millon's reagent (avoid excess) = a red
colour {Hoffmanns test).

15. Leucin. — («.) Under the microscope observe it in the form of brown
balls, with radiating and concentric lines it it is impure ; and, when it is
])ure, as white shining lamella^, with a fatty glance. It is soluble in 27 parts
of cold water, and much less soluble in alcohol.

(//. ) Heated in a tube it sublimes unchanged in very fine clouds with the
odour of amylamine. A part is decomposed into CO., and C5H13N (amylamine).

XI.] THE Brr.E. S7

LESSON XI.
BILE.

1. Use ox-ljilc obtained from the biitclier, and, if possible, human
bile.

(a.) The colour in man is a brownish-yellow, in the ox greenish,
l)ut often it is reddish-brown when it stands for a short time.
Xote its bitter taste, peculiar smell, and specific gravity (loio-
1020).

(b.) It is alkaline or neutral to litmus paper.

(r.) Pour some ox-bile from one vessel to another, and note that
strings of so-called mucin connect one vessel with the other.

{d.) Acidulate bile with acetic acid, which precipitates mucinoid
substance coloured with pigments. Filter off this precipitate. Test
the filtrate.

(f.) It gives no reactions for albumin.

(/'.) Add hydrochloric acid and potassic ferrocyanide. A blue
colour indicates the presence of iron. Test for chlorides and other
salts.

Qf.) Fresh human bile gives no spectrum, although the bile of
the ox, mouse, and some other animals does.

2, Bile-Salts or Bilin (glycocholate and taurocholate of sodium),
(a.) Concentrate ox-bile to one-fourth of its bulk, mix with

animal charcoal in a mortar to form a thick paste. Evaporate to
complete dryness over a water-bath.

(h.) To the dry charcoal-bile mixture, add five volumes of abso-
lute alcohol. Shake the mixture from time to time, and after half
an hour filter. To the filtrate add much ether, which gives a
white precipitate of the bile-salts. If no -sA'ater be present, some-
times the bile-salts are thrown down crystalline ; but not unfre-
quently they go down merely as a milky opalescence, which quickly
forms resinous masses. It is best to allow the mixture to stand
for a day or two, to obtain the glancing needles which constitute
Plattners Crystallised Bile.

Scheme for Bile-SaJU, etc.

200 cc. of ox-bile, dried, mixed with animal charcoal, are extracted with
absolute alcohol by the aid of heat ; filter.

I I

Residue, mucin. Alcoholic solution treated with

pigments, salts, charcoal. ether.

Precipitate, Solution contain?

Bile-salt^. Vholesteriv.

S^ PRACTICAL PHYSIOLOGY. [XI.

3. Pettenkofer's Test for Bile- Acids (Salts) and Cholic Acid.

(a.) To bile in a test-tube, add a drop or two of syrup of cane-
sugar. Pour in conceiitrated sulphuric acid, at the line of junction
of the two fluids a puiyh colour is obtained. Furfuraldehyde is
formed from the action of sugar and sulphuric acid, and the purple
compound is due to the aldehyde compound with cholalic acid. The
white deposit seen above the line of junction is precipitated bile-
acids. They are insoluble in water.

{h.) A better way of doing the test is as folloAvs :— After mixing
the bile and syrup, shake the mixture until the upper part of the
tube is filled with froth. Pour sulphuric acid down the side, and
a purple-red colour is struck in the froth.

{c.) Make a film of bile on a porcelain capsule, add a drop of syrup
of cane-sugar, and then a drop of sulpluuic acid = purple colour.

[d.) Or, after mixing the syrup with the bile, add the strong sulphuric acid
drop by drop, mixing it thoroughly. Heat gently, and the fluid becomes a
deep purple colour. Take care not to add too much syrup, and not to over-
heat the tube. If the requisite amount of sulphuric acid be added, the tem-
perature becomes sufiBciently high (70° C.) without requiring to heat the tube.

{r.) Strassburger's Modification {e.g., for bile in urine). — To the urine add
a little syrup and mix. Dip filter paper into the fluid and dry the paper.
On placing a drop of sulphuric acid on the latter, after some time a purple
spot which has eaten into the paper is observed.

(/. ) Repeat any or all of the above processes with a watery solution of the
bile-salts and with acid albumin.

(f/.) In ])lace of sugar furfurol {Mylius) may be used. Add i drop of fur-
furol solution (i per 1000) and i cc. of concentrated H0SO4.

4. Similar purple colour reactions are obtained with many other sub-
stances— e.g., albumin and o-naphthol, but the spectra differ somewhat.

Albumin and Sulphuric Acid. — To a solution of acid-albumin a-nd syrup
add strong sul])huric acid, a similar tint is obtained. The s})ectra, however,
are different, the red-purple fluid from bile gives two absorjition-bands, one
between E and F, and another between D and E. In the albuminous solu-
tions only one absorption-band exists between E and F.

5. Action of Bile or Bile-Salt« in Precipitating Sulphur.

{a.) In one beaker (A) ])lace diluted bile and in the other (B) water. Pour
flowers of sulphur on both. The sulphur falls in a shower through the fluid
of A, while none passes through B.

{b.) Test to what extent bile may be diluted before it loses this property,
which is due to the diminution of the surface tension by the bile-salts {M. Hay).

(c.) Repeat with a solution of the bile salts.

Bile-Pigments.— The chief are bilirubin (red), blKverdin (green),
and urobilin.

6. Gmelin's Test for Bile-Pigments.

{a.) Place a few drops of bile on a ivliife porcelain slab. With
a glass rod place a drop or two of strong nitric acid containing
nitrous acirl near the drop of bile, bring the acid and bile into
contact. Notice the play or succession of colours, beginning with
green and passing into blue, red, and dirty yellow.

XI.]

THE BILE.

89

(b.) Place a little impure nitric acid in a test-tube. Slant the tube and
pour in bile, a similar play of colours occurs — green above, blue, red, and
yellow below. It is better to do this reaction after removal of the mucin by
acetic acid (Lesson XL 1, d). Or add the nitric acid, and shake after the
addition of every few drops ; the successive colours from green to yellow are
obtained in great beauty. For a modification applicable to urine, see " Urine."

(c.) To green liile + amm. sulphide and shake = reduction to bilirubin.

("'.) To yellow bile + KHO and heat, acidulate with HCl = green due to
oxidation of bilirubin.

7. Cliolesterin and Gall-Stones.

{'I.) Preparation. — Powder a gall-stone and extract it with ether
or boiling alcoliol. Heat the test-tube in warm water, and see that
no gas is burning near it. Drop the solution
on a glass-slide, and examine the crystals micro-
scopically. They are flat plates, with an oblong
piece cut out of one corner (fig, 45). Ethereal
solution gives needles, but a hot alcohohc solution
gives the typical plates.

(6.) Heat crystals in a watch-glass with a few drops
of moderately strong sulphuric acid, and then add
iodine ; a play of colours, passing through violet, blue,
green, red, and brown, occurs.

{(•.) Dissolve crystals in chloroform, add an equal
volume of concentrated sulphuric acid, and shake the
mixture. When the chloroform solution floats on the
top. it becomes blood-red, but changes ijuickly on exposure to the air, passing
tlirough violet and blue to green and yellow. A trace of water decolorises
it at once. The layer of sulphuric acid shows a green fluorescence.

{(/.) The crystals when acted on by strong sulphuric acid become red. Do
this on a slide under the microscope.

(c.) Examine microscopically crystals of cholesterin found in hj'drocele fluid.
The crystals may not be quite perfect, but their characters are quite distinct.

8. Action of Bile in Digestion,

('/.) Action on Starch. — Test if bile converts starch mucilage
into a reducing sugar, as directed for saUva (Lesson VIII.).

(b.) Action on Fats. — 'Mix thoroughly 10 cc. bile with 2 cc.
almond-oil, and observe both by the naked eye and the microscope
to what extent emulsion occurs, and how long it lasts. Compare
a similar mixture of oil and water. In the former case a pretty fair
emulsion will be obtained. In the latter the oil and water separate
rapidly.

('■.) Mix ID cc. of bile with 2 cc. of almond-oil, to which some oleic acid is
added. Shake well, and keep the tube in a water-bath at 40° C. A very
good emulsion is obtained. The bile dissolves the fatty acids, and the
latter decompo.se the salts of the bile-acids : the bile-acids are liberated, while
the fatty acid unites with the alkali of the bile-salts to form a soap. The
soaj) is soluble in the bile, and serves to increase the emulsifying power, as an
emulsion once formed lasts much longer in a soapy solution than in water.

Fig 45 —Crystals of
Cholesterin.

90 PRACTICAL PHYSIOLOGY. [xi.

((/.) Favours Filtration and Absorption. — Place two small funnels ex-
actly the same size in a filter-stand, and under each a beaker. Into each
tunnel put a filter-paiier ; moisten tlie one with water (A), and the other with
bile (B) ; ])our into both an equal volume of almond-oil ; cover with a slip of
glass to prevent evaporation. Set aside for twelve hours, and note that the
oil passes through B, but scarcely any througli A.

(c. ) Effect on the Proteid Products of Gastric Digestion. — Digest some
fibrin in artificial gastric juice, filter, and to the filtrate add drop by drop
ox-bile, or a solution of bile-salts. It causes a white precipitate of peptones
and acid-albumin. The acid of the gastric juice splits up the bile-salts, so
that the bile-acids are also thrown down.

(/. ) Action on Acid-Albumin. — Prepare acid-albumin in solution (Lesson
I. ), and add a few drops of bile — be careful not to add too much — or bile-salts.
This causes curdling of the whole mass. In (c.) and (/. ) it is better to add
bile-salts, because free hydrochloric acid gives a precipitate with bile.

ADDITIONAL EXERCISES.

9. Preparation of Taurin (j8-amidofEthyl-sul])huric acid CoH^NSO;,). —
Mix ox-bile with an excess of strong hydrochloric acid, filter from the slimy
deposit, and evaporate tlie mixture — just under boiling-point— whereby a

tough brownish resinous body separ-
ates—choloidinic acid. Pour oH the
acid watery fluid, concentrate it still
further, until the greater part of the
common salt crystallises out. Mix
the cold mother-liquid with sti-ong
alcohol, whereby taurin is precipitated
along with .some common .salt. Wash
the precipitate with alcohol, dry it,
and dissolve it in a small quantity of
boiling water. On cooling, taurin
separates in four-sided prisms.

10. Cholesterin. — Boil poM'dered
pale gall-stones in water, and then
Fig. 46.— Double-Wallecl Filter for Filtering extract them with boiling alcohol.
HotSolutii.ns. Filter through a double-walled filter

kept hot with boiling water (fig. 46).
The filtrate on cooling precipitates imj)ure cholesterin. Recrystallise it from
boiling alcohol containing potash, wash it with alcohol and water, and
dry the residue over sulphuric acid (fig. 16).

Scheme fur Gail-Stones (Salkowski).
Powdered gall-stones are extracted with ether ; filter.

Solution evaporated Residue (B) treated on the

Cholesterin (A). filter with dilute HCl.

Solution (C) Lime salts. Residue (D) washed with water,

dried, treated with chloroform ;
Bilirubin. I

xilJ glycogen in the liver. 91

LESSON XII.
GLYCOGEN IN THE LIVER.

1. Preparation.

(a.) Feed a rabbit on carrots for a day or longer, or a rat on
oats, and five or six hours after the last meal decapitate it or kill
it by bleeding. Rapidly open the abdomen, remove the Uver, cut one
half of it in pieces, and throw it into boiling "water slightly acidu-
lated with acetic acid. Lay the other half aside, keeping it moist
in a warm place for some hours. After boiling the first portion
for a time, pound it in a mortar with sand, and boil agam. Filter
while hot. The filtrate is milky or opalescent, and is a watery
solution of glycogen and other substances. The acetic acid co-
agulates the proteids, while the boihng "water destroys either a
ferment in the liver or the liver cells, which would convert the
glycogen into grape-sugar.

(/'.) Briicke's Method. — Feed a rabbit on carrots, and after
five or six hours kill it by bleeding. Open the abdomen, rapidly
remove the liver. Some wash out its blood-vessels with a stream
of normal saline. Divide it into two portions. Cut one half as
rapidly as possible into small pieces, and throw the pieces into
boiling water.

Boil them, and afterwards pound them in a mortar and boil
again. Filter while hot, and observe the opalescent filtrate, which
is a solution of glycogen and proteids. The filtrate should flow
into a cooled beaker, placed in a mixture of ice and salt. Pre-
cipitate the proteids by adding alternately hydrochloric acid and
potassio-mercuric iodide (p. 93), until all the proteids are pre-
cipitated. Filter oft' the proteids, and the opalescent filtrate is an
imperfect solution of glycogen. I'o separate llie glijiogen. Evapor-
ate the fluid to a small bulk, and precipitate the glycogen by
adding 96 per cent, alcohol until the solution contains over 60 per
cent, of alcohol. The glycogen is precipitated as a wliite flocculent
powder, wliich is collected on a filter, washed with alcohol and
ether, and then dried in an oven at 100° C. (fig. 47).

(c;) Kiilz's Method. — Feed a rabbit for two days on carrots or boiled
rice. Five or six hours after the last full meal decapitate it, open the
abdomen, rapidly remove the liver ("weigh it), cut it quickly into pieces, and
throw the latter into a large porcelain capsule (400 cc. water to 100 grams
liver) of water boiling briskly. Boil the pieces for about half an hour. Re-
move the pieces, rub them up into a pulp in a mortar (this may be aided by

92

PIIACTICAL 1>HYSI0L0GY.

[xll.

rubbing -with well washed white sand). Replace the pulp in the boiling water
and add 3-4 grams of caustic potash (/>., for 100 grams liver). Heat on a
water-bath and evaporate until about 201 cc. of fluid remains for 100 grams
liver. If a i)ellicle forms on the surf; ce, heat the whole in a beaker covered
with a watch-glass until the pellicle is dissolved. Allow to cool. Neutralise
with dilute hydrochloric acid and precipitate the proteids by adding alter-
nately hydrochloric acid and potassio mercuric iodide in small quantities,
until no further precipitation occurs. Filter through a thick hlter to remove
the deposit of proteids. Remove the deposit from the iilter with a spatula,
and rub it uj) in a mortar with water containing hydrochloric acid and
potassio mercuric iodide, and again filter the pulp. Repeat this process
several times to get out all the glycogen. Mix the filtrates and add 2 volumes
of 96 per cent, alcohol, stirring briskly all the time ; this precipitates the
glycogen. Allow it to stand in a cool place for a night ; filter, and wash the
precipitate thoroughly, first with 62 per cent, and then with q6 per cent.

Fig. 47.— Hot-Air Oven. G. Gas regulator ; E. Thei-mnmeter.

alcohol. Usually the glycogen contains a trace of albumin. To remove the
latter, redissolve the moist glycogen in warm water, and after cooling, repre-
cijiitate with HCl and potassio-mercuric iodide and ])roceed as above. Wash
the glycogen with alcohol and then with ether, and dry it by exposure to the
air. This method gives the most satisfactory result^.

(fL) Instead of a rat or rabbit's liver, use oysters or the edible mussel, and
prepare a solution of glycogen by methods {a.) or {b.).

(e.) Use the other half of the hver of the rat or rabbit that lias
been kept warm, and make a similar extract of it.

2. Precipitate the Glycogen.— Evaporate the filtrate of (a.) or
[h.) to a small bulk, and precipitate the glycogen as a white
powder by adding a large amount of alcohol — at least 60 per cent.

XTI.] GLYCOGEN IN THE LIVER. 93

must be added. Filter ; wash the precipitate on the filter with
absolute alcohol and ether, and dry it over sulphuric acid or in a
hot-air oven (fig. 47).

3. Preparation of Potasslo-Mercuric Iodide or Brlicke's Reagent. — Pre-
cipitate a saturated solution of potassic iodide with a similar solution of
mercuric chloride ; wash the precipitate, and dissolve it to saturation in a hot
solution of potassic iodide.

4. Tests for Glycogen.

(a.) To the opalescent filtrate add iodine solution = a port wine
red or mahogany-brown colour (like that produced by dextrin).
If much glycogen be present the colour disappears, and more iodine
has to be added. Heat the fluid ; the colour disappears, but re-
appears on coohng.

N.B. — In performing this test, make a, control-experiment. Take two test-
tubes, A and B. In A place glycogen solution ; in B, an equal volume of
water. To both add the same amount of iodine solution. A becomes red,
while B is faint yellow.

{h.) To another portion add lead acetate = a precipitate (unHke
dextrin). The solution must be free from proteids and mercuric
salts.

('■.) To another portion add lead acetate and ammonia ; the
glycogen is precipitated (like dextrin).

{d.) Test a jiortion of the glycogen solution for grape sugar. There may be
none, or only the faintest trace.

{e.) To a ])ortion (A) of the glycogen solution add saliva or liquor
pancreaticus, and to another portion (B) add blood, and place both in a
water bath at 40' C. After ten minutes test both for sugar. (A) will be
transparent, and give no reaction with iodine. Perhaps both will give the
sugar reaction; but certainly (A) will, if care be taken that the solution is
not acid after adding the saliva. The ptyalin converts the glycogen into a
reducing sugar.

(/. ) Boil some glycogen solution with dilute hydrochloric acid in a flask ;
neutralise with caustic soda, and test with Fehling's solution for sugar.

5. Test the watery extract of the other half of the hver.
(a.) Perhaps no glycogen reaction, or only a slight one.
(J>.) It contains much reducing sugar.

6. Extract of a Dead Liver.

(a.) Mince a piece of liver from an animal which has been dead
for 24 hours. Boil the liver either in water or a saturated solution
of sodic sulphate. Filter ; the filtrate is clear and yellowish in
tint, but not opalescent.

(/>.) Its reaction is acid to litmus paper.

94

PRACTICAL PHYSIOLOGY.

[xin.

(r.) Test "with iodine after neutralisation with sodic carbonate
and filtration = no glycogen.

(ff.) Test for grape-sugar = much sugar.

After death the glycogen is transformed into grape-sugar unless
precautions be taken to prevent this transformation (p. 91).

LESSON XIII.

MILK, FLOUE, AND BREAD.

1. Milk. — Use fresh cow's milk,
(a.) Examine the " naked-eye " characters of milk.
(b.) Examine a drop of milk microscopically, noting numerous
small, highly-refractive oil-globules floating in a iluid (fig. 48).

(i.) Add dilute caustic soda. The globules run into groups,
(ii.) To a fresh drop add osniic acid. The globules first become brown and
then black.

(iil.) If a drop of colostrum is obtainable, observe the "colostrum cor-
puscles " (fig. 48, C).

(c.) Test its reaction with
litmus paper. It is usually
neutral or slightly alkahne.
(f/.) Take the specific gra-
M vity of perfectly fresh un-
skimmed milk with the
lactometer. It is usually be-
tween 1 028-1034. Take the
specific gravity next day after
the cream has risen to the
surface, or after the cream
Q is removed. The specific
gravity is increased (1033-37)
by the removal of the lightest
constitueiit — the cream.

(e.) Dilute milk with ten

Fig. 48.— Microscopic Appearance of Milk. The times its volume of Water,
upper half, i/, is milk; the lower half, colos.^^^.gf^^yy neutralise it with

dilute acetic acid, and observe
that at first there is no precipitate, as the caseinogen is prevented
from being precipitated by the presence of alkaline phosphates
(Lesson I.). Cautiously add acetic acid until there is a copious

Xm.] MTLK, FLOUR, AND BREAD. 95

granular-looking precipitate of caseinogen, which, as it falls,
entangles the greater part of the fat in it. Precipitation is hastened
by heating to 70° C.

(/.) Filter (e.) through a moist plaited filter. Keep the residue
on the filter. The filtrate is clear. Divide it into two portions.
Take one portion, divide it into two, and boil one = a pre-
cipitate of lactalbumin (serum-albumin). Filter, and keep the
filtrate to test for sugar. To the remainder add potassic ferro-
cyanide, which also precipitates serum-albumin.

{;/.) Test the second half of the filtrate for milk-sugar. Instead
of proceeding thus, test for the presence of a reducing sugar with
the filtrate of (/.) after the separation of the serum-albumin.

(h. ) Scrape off the residue of casein and fat from the filter ( /. ) : wash it with
water from a wash-bottle, and exhaust the residue with a mixture of ether
and alcohol. On placing some of the ethereal solution on a slide, and allowing
it to evaporate, a greasy stain of fat is obtained.

(/. ) To fresh milk add a drop of tincture of guaiacum, which strikes a blue
colour ; boiled milk is said not to do so.

Separation of the Chief Constituents of Milk (Salkowski).
Milk diluted with water, precipitated with acetic acid and filtered.

Filter-residue ''A) (Caseinogen Filtrate (BV flact-albumin, milk-

-t- Fat). Extract with sugar, salts), concentrated by

Ether. evaporation.

i I

.1 III

Residue : Solution Coagulated Further evaporated

CaseincKien, still evaporated Albumin (E). Calcic pho-phate (F),

with fat (C). Butter fat (D). Milk sugar (G).

2. Separation of Caseinogen by Salts. — Saturate milk with
magnesium sulphate or sodium chloride.

The caseinogen and fat separate out, rise to the surface, and leave
a clear fluid beneath. Caseinogen, like globulins, is precipitated by
saturation with ^"aCl, or jNfgSO^, but it is not coagulated by heat.
It was at one time supposed to be an alkali-albumin, but the latter is
not coagulated by rennet. It appears to be a nucleo-albumin (?).
/.''., a compound of a proteid with nuclein, the latter a body rich in
phosphorus.

Precipitation of Caseinogen by MgSO^.

Filter residue Filtrate : Milk, sugar,

Fat -I- Caseinogen. albumin, salts.

Collect the precipitate of caseinogen and fat on a filter and wash it with a

96 PRACTICAL PHYSIOLOGY. [Xllf

saturated solution of MgSO^. Add distilled water, which in presence of the
MgS04 dissolves the caseinogen, which passes through the filter and is col-
lected. From the solution of caseinogen in weak MgSO^ precipitate the
caseinogen by excess of acetic acid. To get the caseinogen quite pure it must
be redissolved in weak alkali or lime water, and precipitated and redissolved
several times.

The filtrate after precipitation of caseinogen contains the lactalbumin, and
can be completely precipitated by saturation with sodium sulphate. It coagu-
lates between 70" and 80' C, and does not seem to be separated into several
proteids by fractional heat coagulation.

The fluid contains lactose, salts, and serum-albumin. Filter.

3. Separation of Caseinogen and Fat by Filtration. — Using a Bunsen's
]>ump, filter milk through a porous cell of porcelain. The particulate matters —
caseinogen and fat — remain behind, while a clear filtrate containing the other
substances })asses through. The porous cell is left empty
and fitted with a caoutchouc cork with two glass tubes
tightly fitted into it. One tube is closed with a clip (fig. 49),
and the other is attached to the pump Place the ]iorous
cell in an outer vessel containing milk. On exhausting
the porous cell a clear watery fluid slowly passes through.
Test it for proteids and sugar. Notice the absence of fat
and caseinogen.

4. Souring of Milk. — Place a small quantity
of milk in a vessel in a warm place for several
days, when it turns sour and curdles. It becomes
r 11 ^^^^ — ^^^^ ^^^^^ (Lesson IX. 10) — having under-
fo'r'* the Filtration gone the lactlc acid fermentation, the lactose
of Miiif. being split up by a micro-organism into lactic acid.

5. Butter, — Place a little milk in a narrow, cylindrical, stoppered
bottle ; add half its volume of caustic soda and some ether, and shake
the mixture. Put the bottle in a water-bath at a low temperature ;
the milk loses its white colour, and an ethereal solution of the fats
floats on the surface. On evaporating the ethereal solution, the
butter is left behind.

6. Curdling of Milk.

(a.) By an Acid. — Place some milk in a flask ; warm it to 40°
C, and add a few drops of acetic acid. The mass clots or curdles,
and separates into a solid curd (caseinogen and fat), and a clear
fluid, the whey, which contains the lactose. Filter.

(h.) By Rennet Ferment.— Take 5 cc. of fresh milk in a test-
tube, heat it in a water-bath to 40° C, and add to it a small
quantity of extract of rennet, or an equal volume of a glycerin
extract of the gastric mucous membrane, which has been neutral-
ised with dilute sodic carbonate, and place the tube again in the
water-bath at 40° C.

Observe that the whole mass curdles in a few minutes, so that

Xlir.] MILK, FLOUR, AND BREAD. 97

the tube can be inverted without the curd falling out. By-and-by
the curd shrinks, and squeezes out a clear slightly-yellowish fluid,
the whey. Filter.

(c.) Using commercial rennet extract, repeat (/>.), but boil the
rennet first ; it no longer effects the change described above. The
rennet ferment is destroyed by heat.

{(/.) Boil the milk and allow it to cool, then add rennet ; in all
probability no coagulation will take place. Boiled milk is far more
difficult to coagulate with rennet than unboiled milk.

(''.) Take some of the curd of 6 (o.). Dissolve one part in caustic
soda and the other in lime-water. Add rennet to both, warm to
40° C. The lime solution coagulates, the soda solution does not.
(The ferment of rennet has been called rennin.)

7. The Salts.

{a.) Using the filtrate of 6 {a.), add magnesia mixture — Lesson
XVII. 7, (7.), i.e., ammonio-sulphate of magnesia, which gives a
precipitate oi phosphates. Calcium phosphate is the most abundant
salt. There is a little magnesium phosphate.

(Ik) Silver nitrate gives a precipitate insoluble in nitric acid,
indicating rhlurides (chiefly potassium and sodium).

8. Boil milk in a porcelain capsule for a time to cause evapora-
tion. It is not coagulated, but a pellicle forms on the surface.
Remove it and boil again ; another pellicle is formed.

9. Coagulation of Milk. — Calcium salts seem to play an important part in
this process.

(i. ) Halliburton's Metliod. — Prepare pure caseinogen by saturating milk
with powdered MgSO^. Allow it to stand for a few hours and filter. Keep
the filtrate (A). Tlie filter residue consists of caseinogen -f fat; wash this with
saturated solution of ilgS04 until the washings contain no albumin. On
adding water to tlie precii)itate, it dissolves, the fat remaining in tlie filter.

Precipitate the solution of caseinogen in weak MgSO^ by acetic acid. Collect
the precipitate on a filter and wash the acid away with distilled water.
Dissolve the ]>recipitate in lime water, rubbing it up in a mortar, filter =
opalescent solution of caseinogen.

Place some of tliis opalescent solution of caseinogen in two tubes A and B.

To A add rennet and keep at 40' C. =no coagulation.

To B add rennet and a few drops of })hos])horic acid (.5 j)ercent. ). Heat to
40' C. = coagulation, i.e., casein is formed horn caseinogen in the presence ot
calcic phosphate.

(ii.) Einger's Method to show the conversion of caseinogen into casein. —
Preci])itate caseinogen ( + fat) with acetic acid. Collect and wash the pre-
cipitate, and grind it up in a mortar with calcium carbonate. Throw the
mixture into excess of distilled water. 1 he fat floats, the excess of calcium
carbonate falls to the bottom, while the very opalescent solution contains the
caseinogen. Divide the fluid into three tubes A, B, C. K^p all at 40" C.

To A add rennet = no clot of casein.

98 PRACTICAL PHYSIOLOGY. [XIII.

To B a few drops of lo per cent, solution of calcium chloride = no clot of
casein.

To C rennet and calcium chloride = clot of casein.

10. Opacity of Milk — Vogel's Laetoscope.

Apparatus required. — A graduated cylindrical cc. measure to hold 200 cc. ;
a laetoscope. with ])arallel glass sides, 5 mm. ajjart (fig. 50) ; a burette finely
graduated : a stearin candle.

Method. — (a.) Be certain, by microscopical examination, that the milk
contains no starch, or chalk, or other granular impurity.
(6.) Mix 3 cc. of milk with 100 cc. of water in the
cylindrical measuring glass.

(c.) In a dark room place the laetoscope on a table,
and I metre distant from it a lighted stearin candle.
Fill the laetoscope with the diluted milk, and look at
tlie candle flame through the glass. If the contour of
Fig. 50.— Laetoscope. the flame can be seen distinctly, jiour back the diluted
milk into the bottle, and add another cc. of milk. Mix
again. Test the mixture again, and repeat until, on looking through the
glass, the outline of the candle-flame can no longer be recognised. Add
together the quantities of milk used. An empirical table constructed by
Vogel gives the percentage of fat,

11. Wheaten Flour. — According to Martin, gluten as such does
not exist in flour. It appears that the two proteids which it con-
tains— vegetable myosin and an albumose — when mixed with water
undergo certain changes, and become converted into the insoluble
proteiil gluten.

(a.) Gluten. — IMoisten some flour with water until it forms a
bough tenacious dough ; tie it in a piece of muslin, and knead it in
a vessel containing water until all the starch is separated. There
remains on the muslin a greyish-white, sticky, elastic mass of
"crude gluten," consisting of tlie insoluble albumenoids, some of
the ash, and tlie fats. Draw out some of the gluten into threads,
and observe its tenacious characters.

(b.) Dry some of the gluten, and heat it strongly in a test-tube ;
an ammoniacal odour similar to tbat of burned feathers is evolved.
Water, wliich is alkaline (due to ammonia), condenses in the upper
part of the tube.

(c.) Extract 10 grams of wheaten flour Avith 50 cc. of water in
a large flask. Shake it from time to time, and allow it to stand
for several hours. Filter. If the filtrate is not quite clear, filter
again. Heat a part of the clear filtrate, and observe the coagula-
tion of vegetable albumin.

(d.) Test another portion of the filtrate from (c.) for the xantho-
proteic reaction.

(e.) Another portion of (c.) is to be precipitated by acetic acid
and ferro-cyanide of potassium.

(/'.) Test a tliird portion of {c.) for the reaction with XaHO and

XIV.] • MUSCLE. 99

C11SO4. This is best seen on slightly heating. Take care not to
boil the liqiiiil, or the reaction for sugar will be got instead.

{(].) Extract some wheaten flour with a 10 per cent, solution of
common salt for twelve hours. Filter, and drop some of the clear
filtrate into a large vessel of water ; a milky precipitate of a
ijJohuUn is obtained.

{Ji.) On saturating some of the filtered saline extract (y.) with
powdered NaCl or MgSO^, a precipitate of a globulin is tlirown
down.

(i. ) Fats. — Shake iij) some wheaten flour with ether in a cylindrical stop-
])ered vessel or test-tube, with a tight fitting cork. Allow the mixture to
stand for an liour shaking it from time to time. Filter off the ether ; place
some of it on a perfectly clean watch-glass, and allow it to evaporate spon-
taneously, when a greasy stain will be left.

(./.) The chief salt is potassium phosphate. The watery extract
gives a yellow precipitate with platinic chloride, showing the
presence of potassium ; while heating it with molybdate of am-
monium and nitric acid gives a canary-yellow precipitate, proving
the presence of phosphates.

12. Pea-Meal.

(a.) Make corresponding watery and saline extracts, and perform
the same experiments with them as in Lesson XIII. 11, (c), (d.),

{e.\ (/•), (r/.). (/'.).

(b.) Observe the copious precipitate on boiling the watery extract,
(c.) Note specially the copious deposit of globulin on adding the
saline extract to water.

13. Bread.

(a.) ^lake a watery extract with warm water, filter, and test the
filtrate. Its reaction is alkaline.

(b.) Test for starch and sugar.

(''.) The insoluble residue gives the xanthoproteic and other
proteid reactions.

LESSON xn^

MUSCLE.

1. Reaction,

(a.) Arrange two strips of glazed litmus-paper, one red and one
blue, side by side. Pith a frog ; cut out the gastrocnemius, remove
as much blood as possible, divide the muscle transversely, and
press the cut ends on the litmus-paper ; a faint blue patch is pro-

lOO PRACTICAL PHYSIOLOGY. [XIV.

diiced on the red paper, showing that the muscle is alkaline during
life. The blue paper is not affected.

(6.) Test the reaction of a piece of butclier's meat ; it is intensely acid, due
to sarco-lactic acid.

(<;. ) Dip the other gastrocnemius into water at 50° C. until rigor caloris
sets in. Test its reaction ; now it is arid.

[d.) Boil some water, and plunge into it any other muscle of the same
frog ; it is alkaline.

('.) Tetanise a muscle for a long time : its reaction becomes acid.

2. Watery and Saline Extracts.

(a.) ^lince some perfectly fresh muscles from a rabbit or dog.
Extract with water, stirring from time to time. After half an
hour, pour off, and filter the watery extract. Re-extract the
remainder with water until the extract gives no proteid reactions.
For the purposes of this exercise, half an hour is sufKcient. Keep
the filtrate, which contains the substances soluble in icater.

(/>.) Take some perfectly fresh muscle from a rabbit, rub it up
with sand in a mortar, and extract it with a large volume of 13
p.c. solution of ammonium chloride, or 10 p.c. XaCl, or 5 p.c.
MgSO^. Stir occasionally, and allow it to extract for an hour. A
stronger extract is obtained if it be left until next day. Pour off the
fluid, keep it, as it contains the substances soluble in saline solutions
— the globulins.

3. With the filtrate of 2 (a.) —

{a.) Test for proteids, e.g., serum-albumin.

{h.) Test the coagulating point of the proteids it contains (45°
and 75° C).

{c.) Add crystals of ammonium sulphate to saturation, which
precipitates all the proteids.

4. Witli the filtrate of 2 {b.)—

{a.) Pour a few drops into a large quantity of water ; observe
the milky deposit of myosinogen. The jjrecijDitate is redissolved
by adding a strong solution of common salt.

{b.) Test the coagulating point. Four proteids are coagulated
by heat at 47", 56", 63°, and 73° C, an albumose being left in
solution. '1 he fluid is acid in reaction.

(r.) Saturate the filtrate with crystals of sodic chloride or
ammonium chloride. The myosinogen is precipitated.

{d.) Collect some of the precipitate of 4 {c), di.ssolve it with a
weak solution of common salt, and test for proteid reactions
(Lesson I. 1). Repeat 3 {c).

(*;.) Suspend in the fluid a crystal of rock-salt ; the latter soon becomes
coated with a deposit of myosinogen.

XIV.]

MUSCLE.

lOI

6. The Extractives of Muscle. — Prepare Kreatin (C^HgNsOj + HjO)
omitting the others.

(a.) Make a strong watery solution of Liebig's extract of meat. Cautiously
add lead acetate until precipitation ceases, avoiding excess of the lead. Filter,
pass sulphuretted hydrogen through
the filtrate to get rid of the lead.
A pellicle is very apt to form on the
surface. Filter, and evaporate the
filtrate to a syrup on a water-bath,
and set it aside in a cool place to
crystallise. Crystals of kreatin
separate out.

(6.) After several days, when
the kreatin has separated, pour
off the mother-liquor, add to it 5
volumes of 90 per cent, alcohol to precipitate more kreatin. Filter, wash
the crystals with alcohol, redissolve them in boiling water, allow them to
recryst.dlise, and examine them with the microscope (fig. 51).

Sarkin and xanthin may be prepared from the alcoholic filtrate of {b. ).

Tlie following scheme after Salkowski shows the process of making
it from flesh.

Preparation of Kreatin.
Minced flesh, digested with water, strained.

Fig. 51.— Crystals of Kreatin.

Filtrate heated to
boiling, filter.

Residue.

Filtrate + lead acetate
filter.

Residue = coagulated
albumin.

Filtrate + BUS to remove

lead, filtrate concentrated

= Kreatin.

Deposit = phosphate

chloride and sulphate

of lead.

6. Liebig's Extract of Meat.

(a.) Te.st it for proteid.s ; they are absent.

(6.) Test it for glycogen, doing a control test. It usually con-
tains a small quantity.

(c.) Test it for kreatinin (see "Urine"). Weyl's test usually
succeeds.

(d.) Examine it microscopically ; in addition to a few crystals
of common salt, a few clear knife-rest forms, there are numerous
crystals of kreatin.

ro2

PRACTICAL PHYSIOLOGY.

[XiV.

ADDITIONAL EXERCISES.

7, Muscle-Plasma. — Kill a rabbit by bleeding from the carotids, open the ,
abdomen, insert a cannula in the aorta, and wasli out all the blood from the
lower limbs by means of a stream of cold saline solution (0.6 per cent.,
NaCl). The solution is made cold enough by ])lacing lumps of ice in it.
Skin the limbs quickly, cut oil pieces of the muscle and plunge them into a
mixture of salt and ice (i'- 2^ C. ), where they quickly become quite hard and
frozen. When they are frozen remove them from tlie mixture, wipe them
with blotting-paper, and place them on a plate kept cold by ice and salt
mixture. Cut them into fine slices (cutting parallel to the direction of the
fibres). Wrap the slices in linen and squeeze them in a pair of cooled enamelled
iron lemon-squeezers ; a yellowish, viscid alkaline plasma is obtained, which
sets in the course of an hour or so into a solid jelly, with the simultaneous
appearance of an acid reaction. By-and-by a clear clot of myosin and a fluid
muscle serum is obtained, just as in a blood-clot. The muscle-plasma con-
tains several proteids. For full details of these see Halliburton, Journal of
Physiology, viii. p. 133.

8. Halliburton's Researches on Proteids of Muscle. — With a stream of
normal saline solution wash out the blood-vessels of a rabbit just killed. Do
this by placing a cannula in the aorta. Remove the muscles quickl}', chop
them up and extract for a day with 5 per cent, solution of magnesium sul-
phate. This is done by the demonstrator. Use this fluid.

(«.) It is probably acid due to lactic acid. Test for this (p. 78).
(6.) Coagukdioa. Dilute some with 4 vols, of water, divide it into two
parts, keep one at 40" C. (rapid coagulation) and the other at the ordinary
temperature (coagulation, but slower). Clot of myosin formed in both.

(c.) Remove the clotted myosin from (b.) ; it is readily soluble in 0.2 per
cent. HCl, forming syntonin ; and also in 10 per cent, sodium chloride.

(d.) Add a few drops of 2 per cent, acetic acid to some of the extract =
stringy piecijntate of myosinogen.

(e.) Perform fractional heat coagulation {HaUihurlon), p. 11.

"(i. ) With the original extract coagula are obtained at 47°, 56°, 63°, 73° C.
" (ii.) With liquid (salted muscle-serum) from ib.), after separation of the

clot, coagula are obtained at 63° and 73° C.
"(iii.) With muscle-extract which has been saturated with MgSOj and
filtered. The globulins are thus se])arated. Coagulation now occurs
at 73° C, but the coagulum is small."
The following table from Halliburton shows these facts : —

Nams of Proteid.

Coagulation
Temperature.

Action of M«so,.^^^li;;;;;;;l:;

Fate.

Myosinogen
Myosinogen.
Myo-globulin.
Myo-.albuniin.

47° C.

56° C.
63° c.

73° C.

Precipitated.
Not precipitated.

Globulin.
Albumin.

\_ Tliese form muscle-clot
) or Myosin.
)^ These are left in mvscle-
) serum.

9. Pigments of Muscle.

{a.) Notice the difference between the red (semi-tendinosus) and pale muscles
(adductor magnus) of the rabbit.

{b.) The muscular part of the diaphragm shows the spectrum of oxy-h:^mo-
globin, even after the blood-ves&els have been washed out Ijy salt solution
(Kiihne).

XV.]

SOME IMPORTANT OROANIC SUBSTANCES. IO3

(c.) A piece of the great pectoral muscle of a pigeon, either fresh or which
has been placed in glycerine to render it more transparent, on being pressed
between two pieces of glass shows absorption hands of mjo-hsematin. {Jlac-
Mimn.) Map out their position with the spectroscope.

LESSON XV.
SOME IMPORTANT ORGANIC SUBSTANCES.

1. Hydrochloride of Glycosamin. — The chitinous parts of crabs and lob-
sters are freed as much as possible from their soft parts, dried, and divided
into small pieces, which are decalcified in dilute hydrochloric acid. Gently
boil the decalcified parts for 3-4 hours with hydrochloric acid, then evaporate
and allow to crystallise. On cooling, a dark brown humus substance and
crystals separate out. Filter, dissolve the crystals in water, and re-evap-
orate until crystallisation takes place. The hydrochloride of glycosamin
(CgHjijNO^HGl) separates in colourless glancing crystals about the size of a
pea, which readily reduce Fehling's solution on boiling. They have a some-
what sweet taste like sugar.

2. Nuclein of Yeast. — Mix i part of fresh German yeast with 4 parts o<^
water, allow the de])0sit to subside. Pour off the turbid fluid from the si;, -
dejiosit of yeast, jilace the latter in .5 ])er cent, caustic ])otasli, stir for some
time, and filter directly into dilute hydrochloric acid. The deposit is filtered
off, washed with dilute hydrochloric acid, and then with alcohol. It is then
boiled with alcohol and dried over sulphur'c acid.

[a.) It is an amorphous powder, insoluble in water and dilute acids, but
readily soluble in alkalies.

ill.) Fuse a little with sodic carbonate and nitrate of potash = a mass witli
a strongly acid reaction due to phosphoric acid.

3. Lecithin.

ro.Ri

C,H J O.R

Mopol^^

Extract the fresh yellow of eggs free from white, with ether, until the latter
takes up no more. Distil ott' the ether, dissolve the residue in ])etroleum
ether, and filter. Extract the filtrate in a separation filter several times with
75 per cent, alcohol. Mix the alcohol extracts, let them stand until they
become clear, separate any petroleum ether, and filter. The rest of the petro-
leum ether is got rid of by distillation, and the residue is exposed for several
days to tlie air in a cool place, M-hereby a deposit sejiarates. The clear fluid
is decanted and filtered. Decolorise it by boiling with animal charcoal, filter
and evaporate to a thick syrup at 50-60^ Dissolve the syrup in ether and
evaporate, and the nearly pure lecithin remains behind [Drechscl).

^ R= radical of palmitic acid (GjjH^iCO), stearic acid (CjyH^jjGO), or oleic
acid (C17H33CO).

104 PRACTICAL PHYSiOtOCY. [XVl.

(a.) It is a soft doughy indistinctly crystalline body. Place a little under
a microscope, add a drop of water, and observe tlie oil-like drops assuming
worm-like forms, so-called " myelin -forms."

(b.) Heat some on platinum, either alone or with sodic carbonate and
potassic nitrate = a residue, strongly acid, in which phosphoric acid is readily
detected.

(f.) Action on Polarised Light. — Examine a little under a polarisation
microscope. With crossed Nicol's each granule of the substance shows a
dark cross on a white ground, just like starch {Dastre).

4. GlycocoU.— C | ^j^ CO.OH | ^^HsNO., or amido-acetic acid.

Preparation. — Boil i part of hippuric acid with 4 parts of dilute sulphuric
acid (i : 6 water) for ten to twelve hours in connection with a condenser.
Carefully pour the mass into a capsule and let it stand for twenty-four hours.
Filter, wash the benzoic acid in the filter with cold water, concentrate the
filtrate by evaporation, and fi-ee it from the last traces of benzoic acid by
shaking it with ether. Dilute strongly the acid solution, and neutralise it
exactly with baryta water. Allow the precipitate to subside, decant, wash
the precipitate with warm water, again concentrate the filtrate until crj'stals
begin to separate on its surface. Allow it to stand twenty -four hours, pour
off the mother-liquid, and again evaporate the latter until other crystals are
formed. The crystals are recrystallised from water.

GlycocoU forms clear colourless crystals, with a sweet taste, readily soluble
in water, and insoluble in alcohol.

5. Guanin Reaction. — Guanin occurs in very considerable quantity in the
skin of fishes and frogs. Heat a small j)iece of the skin from the belly of a
frog, and heat it on a porcelain capsule with HNO, as for the murexide test
(p. 128). Add caustic soda = orange to cherry-red colour. There is no re-
action with ammonia. If there be very little guanin, add dilute caustic
potash, and blow on the stain to cool it, when the latter will pass through
several nuances from blue to orange.

6. Nucleo-Albumin, called " tissue-fibrinogen " by Wooldridge, is best jft-e-
pared by Halliburton's method.

Sodium Chloride Method. — The finely divided thymus gland is ground up
in a mortar with an equal volume of sodium chloride. The viscous mass, on
being poured into excess of distilled water, forms stringy masses which rise to
the surface. Collect and dissolve these in i per cent, sodium carbonate
solution. A few cc. of a clear filtered solution injected into the blood-vessels
of a rabbit produce extensive intra - vascular clotting, especially in the

LESSON XVI.
THE URINE.

1, Urine is a transparent light-straw or amber-coloured watery
secretion derived from the kidneys, containing nitrogenous or
azotised matters, salts, and gases. The most abundant constituents
are water, urea, and sodium chloride. It has a peculiar odour, bitter
saltish taste, and acid reaction.

XVI.]

THE URINE.

T05

2. Quantity. — Normal. — About 2^ pints (50 ounces) or 1500
cc. in twenty-four liours, although there may l)e a considerable
variation even in health, the quantity being regulated Vjy the
amount of fluid taken, and controlled by the state of the tissues,
the pulmonary and cutaneous excretions.

Collection. — It should be collected in a tall graduated glass
cylinder of a capacity of 2500 cc. with a groiuid glass top to
exclude impurities. Samples of the mixed urine of
the ?4 hours are used for examination.

Increased by drinking water {urina potus) or diuretics ; when
the skin is cool, its blood-vessels are contracted, and the cutaneous
secretion is less active ; after a paroxysm of hysteria, and some
convulsive nervous diseases ; in difbetes iiisipi'/us and d. mellUus;
some cases of hypertrophy ot the left ventricle, and some kidney
diseases. The increase may be temporary or persistent, the
former as the effect of cold, diuretics, or nervous excitement ;
the latter in diabetes and certain forms of kidney-disease.

Dimiiiislird after profuse sweating, diarrhcea ; early stage of
acute Bright's disease ; some forms of Bright's disease , the
last stages of all forms of Bright's disease ; in general dropsies ;
in acute febrile and inflammatory diseases.

3. Colour. — Normal. — Light-straw to amber-coloured.
The colour varies greatly even in health, and is due
to the presence of a mixture of pigments, probably
largely derived from the decomposition of haemoglobin.
Of these pigments urobilin, an iron-free derivative of
Hb, is the chief. The colour largely depends on the
degree of dilution of the urine pigments.

r<dc after copious drinking, in diabetes, ancemia, and chlorosis;
after paroxysmal nervous attacks (hysteria). N.B. — Pale urines
indicate the absence of fever.

High-coloured after severe sweating, violent muscular exercise,
diarrhoea, or during febrile conditions.

I'aOwlogiral piijnicids, purpurine or uro-erythrine in febrile
disorders ; bile pigments ; blood.

Medid^ial Sid'slances. — Creosote and carbolic acid make urine
nearly black. This is due not to carbolic acid, but to hydro-
chinon. Sometimes these urines become almost black on stand-
ing ex])0sed to the air. Rhubarb (gamboge-yellow) ; senna
(brownish).

1000

1010

mo

._108O

—1040

Fig. 52.
Urinometer.

4. Specific Gravity. — Normal, s.g. 1020 (1015-
1025). — 'ihis is taken by means of the urinometer
(fig. 52). The instrument ought to be tested by placing it in a
cylindrical vessel filled with distilled water to ascertain that its
zero is correct.

(a.) Fill a tall cylindrical vessel with urine, and place the

I06 PRACTICAt PHYSIOLOGY. fxVI.

urinometer in it. Bring the vessel to the level of the eye, and as
soon as the instrument comes to rest, read off tlie mark on its
stem opposite the lower surface of the meniscus against a bright
hack-ground.

Precautions. — i. The vessel must be so wide that the urinometer can float
freely and not touch the sides. 2. The iiistrunient must be dry before being
placed in tlie fluid. 3. The urine itself must be clear and free from air-
bubbles on the surface ; the latter can be readily removed by means of a fold
of blottingiiajier. N.l>. — It is always necessary to take the specific gravity
of the ■' mixed " urine of twenty-four hours.

Low S.G. — Under normal conditions the s.g. varies inversely as the quantity
of urine passed. All causes which increase the water of the urine only, e.g.,
drinking on an empty stomach ; after hysteria ; in diabetes insipidus or poly-
dipsia. N.B. — If continually below 1015, suspect f^i«ic^es Misi};iV^HS or chronic
Bright's disease.

High .S'.(r.— When the urine is concentrated, diabetes mellitns, due to a
large amount of grape sugar ; first stages of acute fevers ; rapid wasting of
the tissues, especially if as.sociated with sweating or diarrhcEa. It is highest
normally three to four hours after a meal ; and as it varies during the day, it
is necessary to mix the urine of the twenty- four hours, and test the sjjecific
gravity of a sample of the "mixed urine." N.B. — If above 1025 and the
ai'ine be pale, susjject saccharine diabetes.

5. Estimation of the Amount of Solids from the S.G. — By

C I ir 1st ison^s formula {" Hdser-Trcqjj^'s coejficmit "), "multiply the
last two figures of a specific gravity expressed in four figures by
2.33. This gives the quantity of solid matter in every 1000 parts,"
i.e., the number of grams in 1000 cc. (33^ oz.).

Example. — Supp ise a patient to pass 1200 cc. of urine in twenty four hours,
and the sp. gr. to be 1022, then

22 X 2.33 = 51.26 grams in 1000 cc.
To ascertain the amount in 1 200 cc.

51.26 X 1200

1000 : 1200 : : 51.26 : .r= -—- = 61.51 grams.

This formula is purely empirical, and is not applicable where the valuations
are very marked, as in saccharine diabetes and some cases of Bright's disease,
where there is a great diminution of urea.

The normal quantity of sohds, or the total solids — sometimes
spoken of as "solid urine" — is about 70 grams (2 oz.) in twenty-
four hours, i.e., 1000 to 1050 grains. Parkes gives an average
of 945 grains per day for an average adult male lietween twenty
and forty years of age. The latter estimate gives about 20 grains
of solids per fluid ounce of urine, or about 4 per cent, of solids.

6. Odour is " peculiar " and " characteristic," somewhat aromatic
in health.

XVI.] THE URINE. IO7

Certain medicinal and otlier substances influence it — turpentine (violets) ;
cubebs, coj)aiba, and sandal wood oil give a characteristic odour, and so do
asparagus, valerian, assafcctida, garlic, &c. In iHseasf, note the animoniacal
odonr of putrid urine and the so-called ' ' sweet " odour in saccharine
diabetes.

7. Reaction. — Normal. — Slightly acid, it turns blue litmus-
paper slightly red, and does not affect red htmus-paper. The
acidity is chiefly due to acid sodium phosphate (XaHoPO^), acid
urates, and very slightly to free acids — lactic, acetic, oxalic, ko.
A neutral urine does not alter either blue or rod litmus-paper. A
rery acid urine turns blue litmus-paper very red.

{a.) Test with appropriate litmus-paper a normal, very acid,
neutral, and alkaline urine.

{l>.) Test also with violet htmus-paper,

(r.) That the acidity is not due to a free acid is shown by its
giving no precipitate with sodium hyposulphite, and also by the
fact that it has no action on congo-red. The colour of the latter
body is violet or inky, with a solution containing i part of free
hippuric acid in 50,000 of distilled water,

8. Variations in Acidity during the Day. — During digestion, i.e.,
two or three hours after a meal, the urine becomes neutral or alka-
line. The cause of the alkalinity, is a fixed alkali, probably derived
from the basic alkaline phosphates taken with the food {Ruherls),
the ''' aJicaline-tid'\" According to others, the formation of free
acid in the stomach liberates a corresponding amount of bases in
the blood, which pass into the urine, and diminish its acidity or
even render it alkaline. The " acid-tide " occurs after fasting.

Nature of the FoorL — With a vegetable diet the excess of alkali causes an
alkaline urine. In herbivora it is alkaline, in carnivora very acid. Herbivora
(rabbits) whilst fasting have a clear acid urine, because thej' are practically
living on their own tissues. Perhaps this is one of the reasons why the urine
is so acid in fevers. Inanition renders the urine very acid {Chossnt). In
herbivorous animals and vegetarians, the excess of alkaline salts of citric,
tartaric, and other acids being oxidised into carbonates render it alkaline.

Medicines. — Acids slightly increase the acidity. Alkalies and their car-
bonates are more powerful than acids, and soon cause alkalinity ; alkalies,
e.g., the alkaline salts of citric, tartaric, malic, acetic, and lactic acids, appear
as carbonates ( IViJhlcr).

9. Alkalinity may be due to the Presence of a Fixed or a
Volatile Alkali. — In the former case, the blue colour of the litmus-
paper does not disappear on heating ; in the latter it does, and the
paper assumes its original red colour,

(".) Test with two pieces of red litmus-paper two samples of
urine, one alkaline from a fixed alkali, and the other from a vola-
tile one. Uoth papers become blue.

io8

PRACTICAL PHYSIOLOGY.

[XYt.

(b.) Place both side by side on a glass slide, heat them carefully,
and note that the blue colour of the one disappears (volatile alkali),
the red being restored, while the blue of tlie other remains (fixed
alkali).

The alkalinity may be caused by the presence of ammonium carbonate
(volatile), derived from the decomposition of urea ; the urine may be ammonia-
cal when passed, in which case there is always disease of the urinary mucous
membrane ; or it may become so on standing — from putrefaction — when it is
always turbid, and contains a sediment consisting of amorphous pliosphate of
lime and triple-phosphate, and sometimes urate of ammonium ; it has an
oHensive ammoniacal odour, and is very irritating to the mucous membrane.

The acidity is increased during the resolution of febrile diseases ; is excessive
in gout and acute rheumatism, and whenever much uric acid is given off (uric
acid diathesis) ; in saccharine diabetes ; when certain acids are taken with the
food (COo, benzoic).

The amount of the acidity may be determined by using a standard solution
of caustic soda (p. i lo).

d~

X2s '■mm^

c«45'

i^^s^v..

5>

i — 6

'..&^'

V A

<fi>:

j<I(}_ 53.— Deposit in "Acid Fermentation " of Uiine. a. Fungus; 6. Amorphous
sodium urate ; c. Uric acid ; d. Calcium oxalate.

10. Transparency. — Observe whether the urine is quite trans-
parent or contains any suspended particles, rendering it more or
less turbid, either when it is passed, or some time afterwards.

11. Fermentation of Urine. — When urine is freely exposed to
the air it undergoes two fermentations — (i) the acid; (2) the
alkaline. The urine at first becomes slightly more acid, from the
formation of lactic and acetic acids (although this is denied by some
observers), then it gradually becomes 7ieutral, and finally alkaline
from putrefaction. It becomes lighter in colour, turbid, and a
whitish heavy precipitate occurs ; a pellicle forms on the surface, it

XVI.]

THE URINE.

109

swarm.s with bacteria, and it has an amraoniacal odour, \vliich i.s
due to the spUtting up of the urea, thiis —

COX.H, + 2li.fi = (NHJ_,C03.

The urea is split up Ijy a fornient formed by tlie ynifrococcipi
ureae. The carbonate of ammonium makes the urine alkahne, and
the earthy phospliates are precipitated because they are insoUible in
an alkaUne urine. The phosphate of Hme is precipitated as such
(amorphous), while the phosphate of magnesia unites witli tlie
ammonia and is precipitated as ammonio-magnesic phosphate or
triple phosphate (MgNH^PO^ + 6H.,0). Part of the ammoni:i
escapes, and in addition to that united to the magnesic phospliate,
some unites with uric acid to form urate of ammonium.

Fig. 54.— Depfi.«?it in Animoniacal Urine (Alkaline Fermentation), a. Animonio-
niagnesium phosphate ; d. Acid ammonium urate ; c. Bacterium urese.

.V./>. — Altliough urine may be kept "sweet" for a long time in
perfectly clean vessels, still when mixed with decomposing matter
it rapidly putrefies. Insist that all urinary vessels be scrupulously
clean ; and that all instruments introduced into the bladder be
properly puritied by carbolic acid or otlier antiseptic.

(a.) Place some normal urine aside for some days, in a warm
place. (Jbserve it from day to day, noting its reaction, change of
colour, transparency, odour, and any deposits that may form in it.
Examine the deposit microscopically (figs. 53, 54).

Fermentation is hatitened by a high temperature, and especially
if the urine be passed into a contaminated vessel, or the urine
itself contain blood, much mucus or pus. It is retarded in a very
acid and concentrated urine.

no PRACTICAL PHYSIOLOGY. [XVII.

ADDITIONAL EXERCISE.

12. Estimation of the Acidity. —This is done by ascertaining the amount
of caustic soda required to exactly neutralise loo cc. of urine. As the soda
solution cannot be prepared by weighing the soda because of the varying
amount of water contained in it, the soda solution must be titrated with a
standard solution of oxalic acid. Make a nornuil solution of oxalic acid by
dissolving 63 grams of dry crystallised oxalic acid in 1000 cc. water, C2H^04
+ 2H.,0= 126 (i.e., half the quantitj' is taken because the acid is dibasic). A
normal solution of caustic soda would contain 40 grams per litre (XaHO), i.e.,
Na = 23, H=i, O=i6) = 4o). i cc. =40 milligrams or .04 gram. Dissolve
150 grams of caustic soda in about 1000 cc. water.

[a.) Preparation of Normal Caustic Soda. — Place 10 cc. of normal oxalic
acid solution in a beaker, add a few drops of alcoholic solution of rosolic
acid (orange solution), and allow the caustic soda solution to drop from a
burette until the rosolic acid gives a rosy-red tint. Suppose that to saturate
the acid 9.2 cc. of the soda solution are added, then to every 0.2 cc. 0.8 cc.
must be added to obtain a solution of which i cc. will correspond to i cc. of

acid, so that for 1000 cc. of caustic soda 9.2 : 1000 : : 0.8 : x I '— =86. 9 )

86.9 cc, water must be added,

{b.) Determine the Acidity of Urine. — Place 100 cc. of urine in a beaker,

and add to it from a burette the normal soda solution (i cc. =0.063 oxalic acid).

It is better, however, to dilute the soda solution to obtain a deci-nonaal solu-

N
Hon — i.e., one tenth as strong). In this case, i cc. = .0063 oxalic acid.

ID

Place strips of red litmus-paper in the fluid, drop in the caustic soda, stir, and
add caustic soda until the litmus begins to turn blue. Sui)pose 15 cc. of

the dilute ( I solution are used, then the acidity of 100 cc, urine =

15x0.0063 = 0.0945 ; and suppose the total quantity of urine passed to be
1500 cc, then the total acidity of the urine passed in twenty- four hours ex-
pressed as oxalic acid= i 417 grams. The result is merely approximative.

LESSON XVIL
THE INORGANIC CONSTITUENTS OF URINE.

TiiK con.stituent.s of the urine may be classified as follows: —

(i.) W'ifer and inorgauir .m/tif.

(2.) Urea and relaticf nitrogenous hodie.^ ; uric acid, xantliin,
guanin, kreatinin, allantoin, oxalurie acid.

(3.) Aromatic substances ; ether-sulpho-acids of phenol, cresol,
pyrocatechin, hippuric acid, (^c,

(4.) Fatty vnn-nitroijeuous bodies; oxalic, lactic, and glycerin-
phosphoric acid.

(5.) I'igments.

(6.) Gases.

X.VII.] THE INORGANIC CONSTITUENTS OF URINE. Ill

The ratio of inorganic to organic constituents is i to 1.2 -1.7.
The amount of salts excreted in twenty- four hours is 16 to 24 grams
(h to I oz.).

1. Water is derived from the food and drink, a small quantity
being formed in the body (normal quantity 1500 cc, or about
50 oz.).

2. Chlorides are chiefly those of sodium (by far the most
abundant) with a little potassium and ammonium, derived chiefly
from the food, and amount to 10 to 13 grams (150 to 195 grams),
or a mean of 12 grams (180 grains). Sodic chloride crystallises
usually in cubes and octahedra. It sometimes forms a combina-
tion with urea, and then it crystallises in rhombic plates.

(a.) Test with a few drops of AgNO. (i pt. to 8 distilled water)
= white, cheesy, or curdy precipitate in lumps insoluble in HXO3.
The phosphate of silver is also thrown down, but it is soluble in
HNO3.

Estimation. — A rough estimate may be formed of the amount
by allowing the precipitate to subside, and comparing its bulk
from day to day.

Variation!), increased in amount when the urine is secreted in excess,
although the NaCl usually remains very constant (| per cent.) ; lessened in
febrile affections, and where a large amount of exudation has taken place, as
in acute pneumonia, when chlorides may be absent from the urine. The
reappearance of chlorides in the urine is a good symptom, and indicates an
improvement in the condition of the lung. N.B. — The urine ought to be
tested daily for chlorides in cases of pneumonia.

(h.) Evaporate a few drops of urine on a slide = octahedral or
rhombic crystals, a compound of XaCl and urea.

(''.) Test urine from a case of pneumonia, and compare the
amount of the precipitate with that of a normal urine.

3. Quantitative Estimation of Chlorides. — {1.) Slaiuhn-d Silver Xitrate. —
Dissolve 29.075 grams fused silver nitrate in 1000 cc. distilled water, i cc.
= 0.01 NaCI.

(2.) Saturated Solution 0/ Neutral Potassic C'kroniafc.

(a.) Dilute 10 cc. of not too dark-coloured urine with 100 cc. water, and
place it in a beaker; add a few drops of (2). Allow the silver solution to drop
in, stirring all the time until a faint orange tint indicates that there is an end
of the reaction. Deduct i from the number of cc. of the silver solution
added.

4. Sulphates are chiefly those of sodium and potassium. The
total quantity of sulphates (45 to 60 grs.) is 3 to 4 grams daily.
Only a small amount of them enters the body with the food, so that
they are chiefly formed from the metabolism of proteids in the
body. They have no clinical significance. Sulphuric acid, how-

112 PRACTICAL PHYSIOLOGY. [XVII,

ever, exists in urine not only in combination with alkalies, as
indicated above, so-called "preformed sulphuric acid," but also
"with organic radicles, phenol, skatol, and other aromatic siibstances
forming aromatic ether-sulpho-t?ompounds, or "ethereal sulphates,"
the "comb'ned sulphuric acid." The latter form about yLth of
the total sulphates, and originate from j)utrefactive processes in the
intestine. The chief ethereal sulphates are phenol-sulphate of
potassium and indoxyl-sulphate of potassium or indican (CgHgN)

(a.) Test with a soluble salt of barium (the nitrate or chloride)
= white heavy precipitate of barium sulphate, insoluble in HNO3.

{/>.) To separate the combined (ethereal) sulphuric acid. — ]\Iix
50 cc. of urine with an ecpial bulk of " baryta mixture." Stir and
filter. This removes the ordinary sulphuric acid as sulphate of
barium. Add 10 cc. HCl, and keep in a water-bath at 100° C. for
an hour and then allow the ethereal or combined sulphates to
settle.

5. The Phosphates consist of all-aline and earthy salts in the
proportion of 2 to i. The latter are insoluble in an alkahne
medium, and are precipitated when the urine becomes alkaline.
They are insolulile in water, but soluble in acids ; in urine they are
held in solution by free CO.^. The alkaline phosphates are very
soluble in water, and they never form urinary deposits.

The composition of the |)hosj)hates in urine varies. In acid urine, the acid
salts NaH.,PO^ and Ca(H,P04)o are generally present. In neutral urine in
addition NaaHPO^, CaHPO^, and MgHPO^. In alkaline urine there may be
also Na3P04, Ca^lPOJa Mg3(P04)2.

6. The Earthy Phosphates are phosphates of calciinn (CagPO^).,
(abundant) and magnesium (scanty) MgHPO^ + 7 HgO. Quantity
I to 1.5 grams (15 to 23 grs.). They are precipitated when the
urine is alkaline, although not in the form in which they occur in
the urine (Lesson XVI. 11). They are insoluble in water,
readily soluble in acetic and carbonic acid, and are precipitated by
ammonia.

(r/.) To clear filtered urine add nitric acid, boil, and add baric
chloride, and boil again = a precipitate of baric sulphate. Filter,
and to the cool filtrate add ammonia = a precipitate of baric
phosphate.

Clinical Significance. — They are ivercased in osteomalacia and rickets, in
chronic rheumatoid arthritis, after prolonged mental fatigue, and by food and
drink, and diminished in renal diseases and phthisis.

7. The Alkaline Phosphates are chiefly acid sodium phosphate
(NaH.jPO^), with traces of acid potassium phosphate (KH.jPO^); they

XVII.] THE IXORGAXIC CONSTITUENTS OF URINE. 1 1 3

are soluble in water, and not precipitated by alkalies, and never
occur as urinary deposits. The quantity is 2 to 4 grams (30 to
60 grs.). They are chiefly derived from the food, and perhaps
a small amount from the oxidation of the phosphorus of nerve-
tissues.

(a.) To fresh, clear-filtered urine add ammonia, caustic soda, or
potasli, and heat gently until the phSsphates begin to separate ; let
it stand for some time = a white precipitate of the earthy phosphates.
Allow it to stand, and estimate approximately the proportion of the
deposit. [If a high-coloured urine be used, the phosphates may go
down coloured.]

(//.) To urine add about half its volume of nitric acid, and then
add solution of ammonium molybdate and boil - a canary -yellow
crystalline precipitate of ammonium phospho-molybdate. X.B. —
The molybdate is apt to decompose on keeping.

(^.) To urine add half its volume of ammonia, and allow it to
stand = a white precipitate of eartliy xjhuxphates. Filter and test
the filtrate as in 7 (/>.).

(V/.) It gives the reaction for phosphates. This method separates
the alkaline from the earthy phosphates.

(''.) To urine add half its volume of baryta mixture [Lesson
XIX. 12 (c)l = a copious white precipitate. Filter and test the
filtrate as in 7 {i\). Jt gives no reaction for phosphoric acid,
showing that all the phosphates are precipitated.

(./'.) To urine add excess of ammonium chloride, and ammonia
= a white precijDitate of earthy p/ios/ihafcs and oxalate of lime.
Filter, and to the filtrate add a solution of magnesic sulphate = a
precipitate of the alkaline phosphates as triple jjhosj)hate. If the
filtrate be tested for phosphoric acid by 7 ('•.), no precipitate will
be obtained.

(f/.) Instead of 7 (/'.), use magnesia mixture, composed of
magnesic sulphate and ammonium chloride, each i part, distilled
water 8 parts, and liquor ammoniae i part. It gives the same
result as in 7 (/.).

(//.) To urine add a few drops of acetic acid, and then uranium
acetate or nitrate = bright yellow or lemon-coloured precipitate
of uranium and ammonium double phosphate — 2^^U,03)XH^PO^.
This reaction forms the basis of the process for the volumetric
estimation of the phosphoric acid.

The other fact connected with the volumetric estimation
of phosphoric acid is, that when a uranic salt is added to a
solution of potassium ferrocyanide, a reddish-brown colour is
obtained.

{i.) To a very dilute solution of uranium acetate add potassium
ferrocyanide ^ a brown colour.

H

114

PRACTICAL PHYSIOLOGY.

[XVIL

8. In some pathological urines the phosphates are deposited on
boiling.

(n.) Boil snch a urine = a precipitate. It may be phosphates or
albumin. An albuminous precipitate falls before the boiling-point
is reached, and phosphates wlien the fluid is boiled. Add a drop
or two of nitric or acetic acid. If it is phosphates, the precipitate
is dissolved ; if albumin, it is ifuciianged.

9. Microscopic Examination. — As tlie alkaline phosphates are
all freely soluble in water, they do not occur as a urinary deposit.
Tlie earthy phosphates, however, may be deposited.

(a.) Examine a preparation or a deposit of calcic phosphate,
which may exist eitlier in the amorphous form or the crystalline
condition, when it is known as '• stellar ji/ios/ihate" (fig. 55).

(h.) Prepare "stellar pliosphate " crystals by adding some
calcium chloride to normal urine, and tlien nearly neutralising.

Fig. 55.— stellar Phosphate.

Fig. 56. — Various Forms of Triple Phosphate.

On standing, crystals exactly like the rare clinical form of stellar
pliosphate are obtained.

(c.) Triple Phosphate or ammonio - magnesic phosphate
Mg(NH^)P04 + 6H.,0 never occurs in normal urine, and when
it does occur, indicates the decomposition of urea to give the
ammonia necessary to combine with magnesium phosphate to form
this compound. It forms large, clear "knife-rest" crystals (fig. 56).

('/.) If ammonia be added to urine, the ammonio -magnesic
phosphate is thrown down in a fcatkerij form, which is very rarely
met with in the investigation of human urine clinically (fig. 57).

10. General Kules for all Volumetric Processes.

(«.) The burette must be carefully washed out with the titrating
solution, and must be fixed vertically in a suitable holder.

XVTI.]

THE INORGAXIC CONSTITUEXTS OF URINE.

115

always

(h.) All aii-bul)bles must be removed from the burette as well as
from the outflow tube. The latter must be quite tilled witli the
titrating solution.

(r.) Fill the burette with the solution up to zero, and
remove the funnel with which it is
filled.

(d.) Read off the burette always in
the same manner, and always allow a
short time to elapse before doing so,
in order to allow the fluid to run down
the sides of the tube.

(e.) The titrating fluid and the fluid
being titrated must always be tlioroughly yj^
well mixed.

(/',) It is well to make two estima-
tions, the first approximate, the second exact

Featlieiy Forms of Triple
Phosphate.

11. Volumetric Process for Phosphoric Acid, with Ferrocy-
anide of Potassium as Indicator. — i cc of the SS. (Uranium
acetate) = .005 gram of phosphoric acid.

grams of
with (iis-

20 parts

35 grams
litre.

Solutions Required. — Sodium Acetate Solution. — Dissolve 100
sodium acetate in 100 cc. pure acetic acid, and dihite the mixture
tilled water to 1000 cc.

Potassium Ferrocyanide Solution. — Dissolve i part of the salt in
of water.

Uranium Nitrate Solution (i cc.=.oo5 gram H:(P04).— Dissolve
of uranium nitrate in strong acetic acid, and dilute the solution to I

Apparatus Required. —Mohr's burette,
fitted in a stand, and jirovided with a
Mohr's clip ; piece ol white ])orcelain ;
tripod stand and wire-gauze; small beaker;
two pipettes, one to deliver 50 cc, the
other 5 cc. ; glass rod.

(a.) Collect and carefully measure ^'
the urine passed during twenty-four
hours.

(b.) Place 50 cc. of the mixed
and filtered urine in a beaker. Do
this with a pipette. Place the beaker
under a burette.

(c.) To the urine add 5 cc. of the
solution of sodium acetate ; mix
thoroughly.

('/.) Fill a ]\!oh.r's burette with
the SS. of uranium acetate up to zero, or to any mark on the
burette. See that the ilohr's clip is tihgt, and that the outr-

O

Fig. 58.— Burutte Meniscus.

it6

PRACTICAL PHYSIOLOCxY.

[xvrr.

flow tube is filled with the SS, Note the height of the fluid
in the burette. Heat the urine in the beaker to about 80° C.
Drop in the SS. (" Standard Solution ") of uranium acetate from
the burette. Mix thoroughly. Test a drop of the mixture from
time to time, until a drop gives a faint brown colour
when mixed with a drop of potassium ferrocyanide.
Do tliis on a white plate.

(e.) Boil tlie mixture and test again. If necessary,
add a few more drops of the SS., until the brown
colour reappears on testing with the indicator.
[Paper may be dipped in the indicator solution and
tested with a drop of the mixture.] Read off' the
number of cc. used.

Example. — Suppose 17 cc. of the SS. are required to
precipitate the pliosphates in 50 cc. of urine ; as i cc. of
SS. =.005 gram of phosphoric acid, then .005x17 = .085
gram of phosphoric acid in 50 cc. of urine. Suppose the
patient passed 1250 cc. of urine in twenty-four hours, then

1250 X. 085 I, • •

50: 1250 : ; .085 : X — ■ — =2.12 grams 01 phosphoric in

twenty-four hours.

:/

isr

Fig. 59.
Erilmanii's Float.

12. Beading off the Burette. — In the case of tlie
burette being filled with a watery fluid, note that the
upper surface of the water is concave. i\lways bring
the eye to the level of the same horizontal plane as
the bottom of the meniscus curve. Fig. 58 shows
how dift'erent readings may be obtained if tlie eye is
placed at different levels, A, B, C.

13. Jlrdmann's Float (fig. 59) consists of a glass vessel
loaded witli mercury, so that it will float vertically. It is
used to facilitate the reading off of the burette. It has a licrizontal line
engraved round its middle, and must be of such a width as to allow it just
to float freely in the burette. Read off the mark on the burette which
coincides with tlie ring on the float.

14. Carbonates and bicarbonates of the alkalies are generally present in
alkaline urine, and are most abundant in the urine of herbivora and vegetarians.
They are derived fiom the oxidation of the organic vegetable acids. Car-
bonate of lime is not normally present in human urine, though it is sometimes
found as a urinary dejiosit.

15. The Lime, Magnesia, Iron, and other inorganic urinary constituents are
comparatively unimportant, and have no known clinical significance.

XVIII.] ORGANIC CONSTITUENTS OF THE URINE. II7

LESSON XVIII.
ORGANIC CONSTITUENTS OF THE URINE.

1. Urea (CONoTT^) is tlie most importaut organic constituent
in urine, and is the chief end-product of the oxidation of the
nitrogenous constituents of the tissues and food. It crystallises
in silken four-sided prisms, with obliquely-cut ends (rhombic
system), and when rapidly crystallised, in delicate white needles.
It has no effect on litmus; odourless, weak cool-bitter taste, like
saltpetre. It is very soluble in water and in alcohol, and almost
insoluble in ether. It is isomeric with — /.''., it has the same empiri-
cal, but not the same structural formula as ammonium cyanate
(NHjCNO. ]t may

( \H
be regarded as a diamid of CO., or as carbamid = C(_) < ■ytj""

Urea represents the final stage of the metamorphosis of albu-
minous substances within the body. j\Iore than nine-tenths of all
the N taken in is excreted in the form of urea.

2. Preparation from Urine. — Take 20 cc. of fresh filtered human
urine, add 20 cc. of bar^'ta mixture — Lesson XIX. 12 {r.) — to preci-
pitate the phosphates. Filter, evaporate the filtrate to dryness in
an evaporating chamber, and extract the residue Avith boiling alco-
hol. Filter off the alcoholic solution, place some of it on a slide,
and allow the crystals of urea, usually long, fine, transparent
needles, to separate out. This is best done by allowing spontaneous
evaporation of the solution to go on in a warm place. Examine
them microscopically (fig. 60, a).

3. Combinations. — Urea combines with acids, bases, and salts.
Evaporate human urine to one-sixth its bulk, and divide the residue
into two portions, using one for the preparation of nitrate, and the
other for oxalate of urea,

4. Urea Nitrate (CII.X.O, HXO3).

(a.) To the concentrated urine add sirov.g pure nitric acd = a
precipitate of glancing scales of urea nitrate, which, being almost
insoluble in HXO.^, separate out in rhomliic plates or six-sided
tables, with a mother-of-pearl lustre, and often imbricate arrange-
ment.

Ii8

PRACTICAL PHYSIOLOGY.

fxviii

(/;.) Examine the crystals microscopically (fig. 60).

(c.) If only traces of urea are present, concentrate the fluid
supposed to contain the urea, place a drop on a slide, put into
the drop one end of a thread, apply a cover-glass, and put a drop
of ptire nitric acid on the free end of the thread. The acid will
pass into the fluid, and microscopic crystals of urea nitrate will
he formed on the thread. After a time examine the preparation
microscopically.

5. Urea Oxalate (CH,N20)2 C2H2O4 + H2O.

(a.) To the other half of the concentrated urine add a concen-
trated solution of oxalic acid. After a time crystals of oxalate of
urea separate.

(h.) Examine them microscopically (fig. 61).

Fig. 60.— a. Urea ; 6. Hexagonal plates: and c. Smaller scales, or rhombic
plates of urea nitrate.

(c.) Add oxalic acid to a concentrated solution of urea = a preci-
pitate of urea oxalate, which may have many forms — rhombic
plates, crystalline scales, easily soluble in water.

(d.) Do the same test as described for urea nitrate (4, r.), but
substitute oxalic for the nitric acid.

6. Urea and Mercuric Nitrate (2CON2H4 + Bgi^O,).-^ + aHgO).

(a.) To urine (after removing the phosphates by baryta mixture)
or urea sohition add mercuric nitrate = a white, cheesy precipitate,
a compound of urea and mercuric nitrate. Liebig's method for the
estimation of urea is founded on this reaction.

!C3i

XVIII.] OKOAXIC CONSTITUENTS OF THE URINE. II9

7. Other Reactions of Urea. — ^lake a strong watery solution
of urea, and ^vith it perform the following tests : —

(a.) Allow a drop to evaporate on a slide, and examine the
crystals Avhich form (fig. 60, a).

(/>,) To a strong solution of urea add purp nitric acid = a jn-ecipi-
tato of urea nitrate (fig. 60, li).

{'■.) To a strong solution of urea add ordinary nitric, acid tinged
yellow with nitrous acid, or add nitrim--<
iicid itself; bubbles of gas are given off,
consisting of carbon dioxide and nitro- ^S f) y~

gen. 0 \} '-' y\

id.) Add caustic potash, and heat. The \|/^ ^^V ^^^

urea is decomijosed, ammonia is evolved, and ^ «^r Q ^^^\ ^

Ammonium carbonate is formed : — C0N.,H4 \ \ . ^ Q

+ 2H,0 = (NH,),C0:;. ' -N*!^ n ^-^*'^/\

(<!.) Mercuric nitrate gives a greyish -white _ ^^^ 1/ n ^\

cheesy precipitate. -i ^^J '-' ^ ^ \J

Fig. 61. — Crystals of Oxalate of

•^-> , ,0

8. With Crystals of Urea perform
the following experiments : —

{11.) Biuret Reaction. — Heat a crystal
in a hard tube ; the crystal melts, ^ ^^' ^frea fiom'i'rine"
ammonia is given off, and is recognised

by its smell and its action on htmus, while a white subHmate of
cyanuric acid (C3H3N3O3) is deposited on the upper cool part of
the tube. Heat the tube until there is no longer an odour of
ammonia. AIIom- the tube to cool, add a drop or two of water to
dissolve tlie residue, a few drops of caustic soda or potash, and a
little very dilute solution of cupric sulphate = a jiink colour (biuret
reaction). Two molecules of urea yield one of biuret.

{h.) Place a large crystal of urea in a watch-glass, cover it with a saturated
freshly jjrepared watery solution o\ fur/iirol, and at once add a drop ot strong
liydrochloric acid, when there occurs a rapid play of colours, beginning with
yellow "and passing through green, purple, to violet or brown. This test
requires care in its perlonnance.

9. Quantity. — An adult excretes 30 to 40 grams (450 to 600
grs.) daily : a woman less, and children relatively more. It varies,
however, with

(a.) Nature of the Food.— It increases when the nitrogenous matters are

120 PRACTICAL PHYSIOLOGY [xiX.

increased in the food, and is diminished by vegetable diet. It is increased
by copious draughts of water, salts. It is still excreted during starvation.

(h.) Muscular Exercise has little ettect on the amount.

(c.) In Disease. — In the acute stage of fevers and inflammation there is an
increased formation and discharge, also in saccharine diabetes (from the large
quantities ot food consumed). It is diminished in anremia. cholera, by the
use of morphia, in acute and chronic Bright's disease. If it is retained within
the body, it gives rise to untmia, when it may be excreted by tlie skin, or be
given oti by the bowel.

10. Occurrence. — Urea occurs in the blood, lymph, cliyle, liver, lympli
glands, spleen, lungs, brain, saliva, amniotic fluid. The chief seat of its
formation is very probably the liver. It also occurs in small quantity in
the urine of birds, reptiles, and herbivora, but it is most abundant in that
of carnivora.

LESSON XTX.
VOLUMETRIC ANALYSIS FOR UREA.

1. Before performing the volumetric analysis for urea, do the
following reactions, which form the basis of this process ; —

(".) To a solution of sodic carbonate add mercuric nitrate = a
yellow precipitate of mercuric hydrate,

(/'.) To urine add sodic carbonate, and then mercuric nitrate =
first of all a white cheesy precipitate ; on adding more mercuric
nitrate, a yellow is obtained, i.e., no yellow is obtained until the
mercuric nitrate has combined with the urea, and there is an excess
of the mercuric salt.

{(•.) To urine add hjDiohromite of soda. At once the urea is
decomposed, and bubbles of gas — IST — are given off.

2. Estimation of Urea by Hiifner's H5rpobromite Method.

The principle of tiiis method depends on tl)e fact that urea is
decomposed by alkaline solution of sodium hypobromite, yielding
water, CO., and N. The CO2 is absorbed by the caustic soda, the
N, which is disengaged in bubbles, is collected and measured in a
suitable apparatus.

Sodium Carbon Sodium

Urea. Hypobromite. Dioxide. Nitrogen. Water. Bromide.

COXgH^ + 3NaBrO = CO., + Ng + 2H2O + sNaBr

Every o.i gram of urea contains .046 gram N; this at the ordi-
nary temperature and pressure = 37.3 cc. of nitrogen. In practice
only 35.43 cc. are obtained. It is an accurate method, and the
one generally used for clinical purposes. Many different forms of
apparatus have been devised, including those of Knop and Hiifner,
Russel and West, Graham Steele, Simpson, Dupre, Charteris,
Gerrard, &c.

XIX.]

VOLUMETRIC ANALYSIS FOR UREA.

121

3. Apparatus and Solutions required.

( i. ) A 40 per cent, solution of caustic sodk.

( ii.) Tubes containing 2 ami 4 cc. of bromine. This is far more con-
venient than tlie (hiid bromine,
(iii.) A strong glass cylinder with a glass stopper,
(iv.) A 5 cc. pipette.
( V. ) Urea apj)aratus, e.g., of Dupre, or Gerrard,

4. Make th" hij »ohromite. solution: Place 23 cc. of the caustic soda solution
in the glass-stojipered cylinder, drop into it
gently a tube containing 2 cc. of bromine.
Shake the cylinder so as to break the
bromine tube ; the soda combines with the
bromine. These bromine tubes can be
purchased. The solution spoils by kee})ing,
so that it should be made fresh for each
estimation.

5. Dupr6's Apparatus.! — In this
apparatiLs (fig. 62) tlie graduation on
the collecting tube represents either
the percentage of urea or cc. of N.
The collecting tube, which is clamped
above, is placed in a tall vessel con-
taining water, and connected with a
small glass flask containing a short
test-tube.

(a.) Remove the short test-tube
from the flask, and in the latter
place 25 cc. of the hypobromite
solution.

{}).) With a pipette measure off" 5
cc. of the clear filtered urine, and
place it in the short test-tube attaclied
to the india-rubber stopper, and seen
on the left side of fig. 62. This
is preferable to the pipette shown
in the fig. Place the caoutchouc
stopper in the flask.

('•.) Test to see if all the connec-
tions are tight. Open the clamp at
tlie upper end of the collecting tube,
depress the tube in the water until
the water inside and outside the tube
is at zero of the graduation,
collecting tube. If the apparatus be tight, no air will pass in

Fig. 62. — Dupr^'s Urea Apparatus.

Close the clamp, and raise th

^ Made by George J. Smith, 73 Farringdon Street.

122

PRACTICAL PHYSIOLOGY.

[XIX.

and on lowering the coUpcting tube the water will stand at zero
inside and outside the tube.

(ff.) Mix the urine gradually with the hypobromite solution by
gently tilting over the flask. Gas is rapidly given off, the COg is
absorbed by the caustic soda, wlaile the N is collected in the
graduated measuring tube.

(e.) Place the flask in a jar of water at the same temperature as
that in the tall jar, and shghtly lower the measuring tube. After

Fig. 63.— Steele's Apparatus for Urea. A. Flask for hypobromite; B. Tube for
urine: C. Burette ; £>. Vessel with water ; E. Vessel with water to cool A.

all effervescence has ceased, and when the X collected in tlie col-
lecting tube has cooled to the temperature of the room - i.e., in five
to ten minutes— raise the collecting tube until the fluid inside and
outside stands at the same level. Eead olf the graduated tube ;
this gives the percentage of urea. Or if the burette be graduated
in cc. read off the number of cc. and calculate the amount of urea
from the amount of N evolved.

It is to be remembered that other bodies in the urine, such as
uric acid (urates) and kreatinin — but not hippuric acid — also yield

XIX.]

VOLUMETRIC ANALYSIS FOR UREA.

123

nitrogen by this process; further, that only about 92 per cent,
of the JN" of the urea is given oft in tlie above processes. These
sources of fallacy are. however, taken into account in graduating
the apparatus.

6. Steele's Apparatus (fig. 63). — Li this apparatus the collect-
ing tube is a graduated burette graduated in cc.

(a.) Use this apparatus in a similar manner. The tube B is
intioduced into the flask A by means of a
pair of forceps.

(b.) Read off the number of cc. of N
evolved, and from tliis calculate the
amount of urea. Every 35.4 cc. X = o.i
gram urea.

7. Ureameter of Doremus (fig. 64). —
It consists of a graduated bulb-tube, closed
at one end. Hypobromite of sodium
solution is poured into the tube up to a
certain mark, and diluted with water to
fill the long arm and bend. The urine
to be tested is drawn into the pipette to
the graduation. The pipette is then passed
into the lu'eameter. as far as the bend,
and the nipple is compressed slowly. The
urine will then rise through the hypo-
bromite solution, and the gas evolved will
collect m the upper part of the tube.

Each divi.sion indicates .001 gram of
urea in i cc. of urine. The percentage of urea present in the urine
is found by simply multiplying the result of the test by 100.

8. Study also Charteris's apparatus. The bromine ai.d caustic soda are
mixed in a marked measure, .so that the hj-pobromite is always IVesh, while
the collecting tube for the IS" is so graduated as to indicate a cerLaiii percentafe
of urea.

Fig. 6^.-

I're.an^eter of Dorennis
with Pipette.

9. Study Squibb's apparatus,
with the apparatus.

In all these cases directions are supplied

10. Liebig's Volumetric Process for Urea with Sodic Carbonate as Indi
cater. — I cc. of the SS. (mercuric nitrate) = .01 gram or 10 milligrams of urea.
This method has been largely supplanted by the hypobromite process.

11. Solutions Required.

Baryta Mixture. -I'lfjiared as in Lesson XIX. 12 (c).

Mercuric Nitrate Solution. — (i cc. = -oi gram urea). Dissolve with the
aid of gentle heat 77.2 grams of pure dry oxide of mercury in as small a
quantity as possible of HISO3, evaporate to a syrup, and then dilute with

124 PRACTICAL PHYSIOLOGY. [XIX.

water to i litre, A few dro])s of HNO3 will dissolve any of the basic salt left
undissolved. N.B. — The exact strength of this solution must he estimated
by titrating it with a standard 2 per cent, solution of urea.
Sodic Carbonate Solution. — 20 grains to the ounce of water.

12. Apparatus Required. — Burette fixed in a stand, funnels, beakers,
filter-paper, glass rod, plate of glass, and three pipettes, 10, 15, and 20 cc.

(a.) Collect the urine of the twenty-four hours, and measure the quantity.

(b.) If albumin be present, separate it by acidification (acetic acid , boiling,
and filtration.

{(■.) Mix 40 cc. of urine with 20 cc, i.e., half its volume, of a solution of
barium nitrate and bariura hydrate (composed of one volume of solution of
barium nitrate and two volumes of barium hydrate, both saturated in the cold).
This precipitates the phosphates, sulphates, and carbonates.

{d. ) Filter through a dry filter to get rid of the above salts. While filtra-
tion is going on, fill the burette with the standard solution (SS.) of mer-
curic nitrate up to the mark 0 on the burette. See that there are no air-
bubbles, and that the outflow tube is also filled.

(c.) With a pipette take 15 cc. of the clear filtrate and place it in a beaker.
N.B. — This corresj)ouds to 10 cc. of urine. Place a few drops of the sodic
carbonate solution (the indicator) on a piece of glass resting on a black back-
ground.

(/.) Note the height of the fluid in the burette. Run in the SS. of mer-
curic nitrate from the burette into the 15 ec. of the mixture, in small
quantities at a time, until the j)recipitate ceases. Stir and mix thoroughly
with a gla:.-s roil. After each addition, with the glass rod lift out a drop of
the mixture and ]'lace it on one of the drops of sodic carbonate until a })ale
yelloii) colour is obtained. This indicates that all the urea has been precipi-
tated, and that there is an excess of mercui'ic nitrate. Read off the number
of cc. of the SS. useil.

{g. ) Repeat the experiment with a fresh 15 cc. of the filtrate, but run in the
greater part of the requisite SS. at once before testing with sodic carbonate.

Read off the number of cc. of the SS. used, and deduct 2 cc. ; multiply by
.01, which gives the amount (in grams) of urea in 10 cc. of urine.

Example. — Sujipose 27 cc. of theSS. were used, and the patient jiassed 1200
cc. of urine in twenty-four hours: then 25 x .01 = .25 gram urea in 10 cc.

1200 X 2 '^
10 : 1200 : : .25 : a; . ' — = -jo grams o.*"urea in tweTity-four hours.

This method yields ajiproximately accurate results only when the amount
of urea is about 2 per cent. With a greater or less percentage of urea, certain
modifications have to be made.

Correction for Sodic Chloride. — Two cc, were deducted in the above pro-
cess. Why? On adding mercuric nitrate to a solution containing sodic
chloride, the mercuric nitrate is decom])Osed and mercuric chloride formed,
and as long as any sodic chloride is present, there is no fi'ee mercuric nitrate
to combine with the urea. Proofs of this : —

{(i.) To a solution of sodic chloride (normal saline) add mercuric nitrate =
no precipitate.

(/'.) To A solution of sodi'; chloride (normal saline) add a few crystals of urea,
then add mercuric nitrate At first there is no precijiitate, or, it there is,
it is i-edissolved ; 1)ut by-and-by a wliite preci{)itate is obtained.

('■.) To a solution of urea (acidj add mercuric chloride = precipitate.

XIX.]

VOLUMETRIC ANALYSIS FOR UREA.

125

ADDITIONAL EXERCISES.

13. Hiifner's Apparatus (fig. 65). — It consists of a stout fusiform glass
cylinder Bj capacity 100 cc. ), connected below by means of a glass tap with
a smaller tube (caiiicity 5 cc. 1. The capacity of A is important, as it contains
the urine, so that it must be previously calibrated. The remainder of the

Fig. 65.— Hiifner's Urea Apparatus.

apparatus consists of a glass bowl (C) fitted by means of a caoutchouc stopper

upon tlie ujiper end of B. Above this is a graduated gas-collecting tube ^D),

40 cm. long and 2 cm. wide, and graduated into 0.2 cm. in units of capacity.

By means of a long funnel fill the vessel A with urine, close the tap, and

126

PRACTICAL PHYSIOLOGY.

[xix.

wash every trace of urine out of B. Place C in position, fill B with a freshly-
I)repared solution of hypobromite, and place a concentrated solution of com-
mon salt in C to the depth of i cm. Fill D also with the salt solution,
avoiding the ])resence of air-bubbles. Insert D over B. Open the tap when
the hypobromite mixes with the urine and the gases are evolved. The quan-
tity of urea is calculated from the volume of N evolved.

14. Garrard's Apparatus (fig. 66\

Method of (Isi'ig. -Pour into the tube 5 cc. of the ui'ine to be examined, and
in the bottle («i 25 cc. or 6 liuid drachms of sodium hypobromite solution.
Place the tube carefully inside the bottle, as shown in the illustration, avoid-
ing spilling any of the contents. Fill tlie glass tubes (h, c) with water, so that

the level reaches the zero-line, tak-
ing care that when this is r'one the
tube (pt contains only a little water
by being placed high — it having to
receive what is displaced from (/); by
the nitrogen evolved. Now connect
tlie india-rubber tubing to the
bottle, and noting lastly that the
water is exactly at zero, upset the
contents of the tube into the hypo-
bromite solution. Nitrogen is
evolved, and de])resses the water in
(b). When this ceases, lower (c)
until the level of the water in both
tubes is equal. To be exact, dip
{a) into cold water to cool the gas
before taking a reading, and note
the result, which shows percentage
of urea.

The solution of hypobromite of
soda is made by dissolving 100
grams of caustic soda in 250 cc. of
water, then adding 22 cc. of
bromine.

To avoid the danger of the bro-
mine vapour, the bromine is sold in
hermetically sealed glass tubes, con-
taining 2.2 cc. ; one of these placed
Fig. 66.— Garrard's Urea Apparatus, as ma.Ie in the large bottle with 25 cc. of the
by Gibbs, Cuxson, & Co., Wednesbury. ^^^^ solu'tion gives, when broken

with a sharp shake, the exact
quantity of liypoliromite for one estimation of urea, and all bad odour is
avoided.

15. Synthetic Preparation o.*' Urea. — Heat coarsely-powdered ferro-
cyanide ot potassium (FeCy.^.4KCy + 3H^0, about 250 grams; over a fire in a
large porcelain vessel. Stir constantly, and heat until the whole assumes a
white colour, and the larger pieces when broken u{) show no trace of yellow.
If it be ovor-heated the powder becomes brown. The white mass is finely
powdered and mixed with half its volume of dry, finely-powdered, black oxide
of manganese. The whole is heated in a black metal pot in a draught
chamber until it begins to scintillate, and the mass becomes doughy. The
mass is heated until a small portion of it, when dissolved in water and after
acidulation with hydrochloric acid, is no longer rendered blue by ferric

XX.]

URIC ACID, ETC. 1 27

chloride. Cool and extract with cold water, and add to the solution dry
ammonium suli)hate to the extent of tliree fourths ot the weight of potassic
ferrocyanide used. Filter, evaporate on a water-bath at about 60^-70' C (at
which temperature ammonium cyanate passes into urea). At first potassic
sulphate crystallises out ; remove it from time to time. Lastly, evajwrate to
dryness, and extract the urea from the residue by absolute alcohol. The urea
crystallises from the alcoholic solution at a moderate temperature {Drechsel).

16. Estimation of Total Nitrogen {rfliKicr and Bohlnvd's Approyimnfive
M'thod. — fi.) Take 10 cc. of urine, add Liebig's mercuric nitrate until a
faint yellow is obtained with a drop of the mixture when the latter is tested
with sodic carbonate. The number of cc. of the SS. used multiplied by 0.04
gives the total N.

(ii.) KjfldahPs Mc/hod. —Thin m.ethod, when once the standardised solutions
are prepared, and the ajiparatus set up, can be carried out in about an liour,
and several estimations can be carried out simultaneously. In tliis method
the organic matter is destroyed by prolonged heating of the substance with
sulphuric acid until the originally blackish fluid becomes clear and yellow
coloured. After it cools, caustic soda is added, the flask is corked, and the
mixture is distilled, whereby the ammonia passes over into a standardised
solution of sulpliuric acid. The ammonia is calculated by titrating the
sidphuric acid with standard caustic soda. (See Sutton's Volutiictric Analysis,
p. 68, 5th edit., 18S6.)

LESSO^^ XX.

URIC ACID— URATES— HIPPURIC ACID —
KREATININ, &c.

1. Uric Acid (CjH^N^Og) contains 33.33 per cent, of X, and,
next to urea, is the constituent of the urine whereby the largest
quantity of X of the Ijody is excreted, whilst in birds, reptik^s,
and insects it forms the chief nitrogenous excretion. The propor-
tion of urea to uric acid is 45 : i.

The following structural formula show its relation to urea, and the results
ol its decomposition : —

KH— CO

CO

C -XH

1

« >C0

NH

C-XH

2. Quantity. — 0.5 gram (7-10 grs.) daily. It is dibasic, colourless, and
crystallises, chiefly in rhombic jilates, and when the obtuse angles are
rounded the "whetstone" form is obtained. It often cr^'stallises s])on-
taneously in rosettes from saccharine diabetic urine. It is tasteless, reddens
litmus, and is very insoluble in water (i!S,ooo parts of cold and 15,000 of
warm water), insoluble in alcohol and ether. In the urine it occurs chiefly in
the form oi OAiid urates of soda (C5H.2N4O3, HNa) aud potash.

128

PRACTICAL PHYSIOLOGY.

[xx.

(a.) In a conical glass, add 5 parts of HCl to 20 parts of urine,
put it in a cool place for twenty-four hours. Yellow or brownish-
coloured crystals of uric acid are deposited on the sides of the
glass, or form a pellicle on the surface of the fluid like fine grains
of cayenne-pepper. Both uric acid and its salts (urates), when
they occur as sediments in urine, are coloured, and the colour is
deeper the more coloured the urine. The slow separation of the
uric acid is probably due to the presence of phosphatic salts.

(h.) Collect some of the crystals and examine them microscopi-
cally. The crystals assume many forms, but are chiefly rhombic.
They may be whetstone, lozenge-shaped, in rosettes, quadrilateral

- d

Fig. 67.— Uric Acid. a. Rhombic tables (wlietstone form): b. Barrel f rin ;
c. Sheaves; d. Rosettes of whetstone crystals.

prisms, &c. They are yellounsh in colour, although their tint may
vary from yellow to red or reddish-brown, depending on the depth
of the colour of the urine (figs. 67, 68).

(c.) The crystals are soluble in caustic soda or potash. Observe
this under the microscope.

('/.) With the aid of heat dissolve some serpent's urine — which
is solid, and consists chiefly of ammonium urate — in a 10 per
cent, solution of caustic soda. Add water, and allow it to stand.
Pour off' the clear fluid, and precipitate the uric acid with dilute
hydrochloric acid. Collect the deposit and use it for testing.

3. Reactions and Tests.

{a.) Murexide Test. — Place uric acid in a porcelain capsule
add nitric acid, and heat gently, taking care that the temperature

XX.

URIC ACID, ETC.

129

is not too high — not above 40° C. Very disagreeable fumes are
given off, while a yellow or reddish stain remains. Allow it to
cool, and bring a rod dipped in ammonia near the stain, or moisten
it with strong ammonia, when a purple-red colour of vmrexidp,
C,H^(NH4)N50^, appears. It
turns violet on adding caustic
potash.

(6.) Repeat the experiment,
but act on the residue with
caustic soda or potash, when
a violet-blue colour — dis-
charged by heat— is obtained.
The latter distinguishes it
from guanin. When uric acid
is acted on by nitric acid,
alloxantin (CgH^N^O-) is
formed, which, on being
further heated, yields alloxan
(C4H2N.^O^) ; the latter strikes
a purple colour — murexide —
with ammonia.

{r.) Place uric acid on a
microscopic slide, and dissolve
it in liquor potassje. Heat,
if necessary ; add hydro-
chloric or nitric acid just to
excess, and examine with the

microscope the crystals of uric acid which form. They may
transparent rhombs with obtuse angles, dumb-bells, or in
rosettes.

('/.) Dissolve uric acid in caustic soda, add a drop or two of
Fehling's solution — or dilute cupric sulphate and caustic soda —
and boil = a white precipitate of cupric urate, which after a time
becomes greenish.

{e.) Schiff's Test. — Dissolve uric acid in a small quantity of
sodium carbonate. Place, by means of a glass rod, a drop of solu-
tion of silver nitrate on tilter-paper, and on this place a drop of the
uric acid solution. A dark brown or black spot of reduced silver
appears.

( /■,) Heat some uric acid in a test-tube. It blackens and gives
off the smell of burnt feathers.

Fig. 68. — Uric Acid. a. Rhoniboidal, truncated,
hexalieiiral. ami laniinated crystals ; b. Riioin-
bii; prism, horizontally truncated angles of
the rhombic prism ; c. Prism with a hexa-
hedral basic surface, barrel - shaped figure,
prism with a hexahedral basal surface ; d.
Cylindrical figure, stellate and superimposed
groups of crystals.

be

{g.) Garrod's Microscopic Tesf. — AiM 6 to 8 drops of glacial acetic acid to
5 cc. urine in a watch-glass, ])ut into it a few silk tliieads, and allow the
whole to stand for twenty-lour hours, taking care to prevent evaporation by

130 PRACriCAL PHYSIOLOGY. [XX.

covering it with another watch-glass or small beaker. Examine the threads
microscopically for the characteristic crystals of uric acid, which are soluble
in KHO. A similar reaction may be done on a microscopic slide.

4. Uric Acid Salts (Urates, " Lithates ").— Uric acid forms salts
(chiefly acid), with various bases, which are sohihle with ditficidty
in cold, but readily soluble in warm water. HCl and acetic acid
decompose urates, and then the uric acid crystallises.

Urates form one ot the commonest and least important deposits in urine.
There is usually a copious precipitate, varying in colour from a light pink or
brick-red to purple. They occur in catarrhal afifections of the intestinal canal,
after a debauch, in various diseases of the liver, in rheumatic and feverish
conditions. They frequently occur as the " milky " deposit in the urine of
children. Urates constitute tlie " lateritious " deposit or " critical " deposit
of the older writers. Urates ft-equently occur even in health, especially when
the skin is very active (in summer), or after severe muscular exercise ; when
much water is given off by the skin and a small quantity by the kidneys.
The following are the formul;^ of the more common urates : —

Acid sodic urate ..... C5H:(N40.;Na.

Neutral sodic urate .... C5H._,N403Na.,.

Acid ammonium urate .... C5H3N403(NH4).

Acid potassic urate .... CgHsN^O^K.

When the urine is passed it is quite clear, but on standing for
a time it becomes turbid, and a copious reddish-yellow — some-
times like pea-soup — or purplish precipitate occurs, because urates
are more soluble in warm water than in cold ; and when there
is only a small quantity of water to hold the urates in solution,
on the urine cooling they are precipitated. 'Jlieir occurrence is
favoured by an acid reaction, a concentrated condition of the urine,
and a low temperature.

The urates deposited in urine consist chiefly of sodic urate mixed
with a small amount of ammonium urate.

5. Tests for " Urates " or " Lithates " in urine.

(a.) Observe the naked-eye characters. The deposit is usually
copious = yellowish-pink, reddish, or even shading into purple.
The deposit moves freely on moving the vessel, and its upper
border is fairly well defined.

(h.) Place some in a test-tube. Heat gently the upper stratum.
It becomes clear, and on heating the whole mass of fluid, it als6
becomes clear, as the urates are dissolved by the warm liquid.

(c.) Place some of the deposit on a glass slide, add a drop of
hydrochloric acid, and uric acid is deposited in one or more of
its many crystalline forms. Examine the crystals microscopically.

if I.) Examine the depo.sit inicroscopically. The urates are
usually " amorphous," but the urate of soda may occur in the form

XX.] URIC ACID, KTC. I3I

of small spheres covered with spines, and the ammonium urate, of
spherules often united together (fig. 77).

(e.) Make a saturated solution of uric acid in caustic soda. Place a drop
of the mixture on a slide, allow it to evaporate. Examine it microscopically,
when the urate of soda in the form of spheres covered with spines will be
obtained.

(/. 1 The same result as in (c. ) is obtained by dissolving the ordinary deposit
of urates with caustic soda, and allowing some of it to evaporate on a slide.

6. TJric Acid from Serpent's Excrement. — Heat the powdered excrement
in a porcelain vessel with 15-20 vols, of water just to boiling, add careful]}'
small quantities of caustic potash or soda until the whole is dissolved and
there is no further odour of ammonia given oft'. Filter, and saturate the
filtrate with CfV,, which causes at first a gelatinous and then a tinely-granular
{irecipitate of acid alkaline urate. Separate the latter by syphoning off the
fluid, wash it with small quantities of iced water, place it in a boiling dilute
solution of hydrochloric acid, and boil the mixture for some time. After it
cools, uric acid crystallises out, the latter is washed with cold water and dried.

7. Hippuric Acid, Cj^H^XOg (benzoyl - amido - acetic acid or
benzoyl-glycin). — This substance is so called because it occurs in
large quantity in the urine of the horse and many herbivora,
cliiefly in the form of alkaline hippurates (sodium hippurate). It
belongs to the aromatic series. It dissolves readily in hot alcohol,
but is sparingly soluble in water.

Quantity in man .5 to i gram daily. It is a conjugate acid, which, when
boiled with alkalies and acids, takes up water and splits into benzoic acid and
glycin. It occurs in colourless four-sided prisms, usually with two or four
bevelled surfaces at their ends. It has a bitter taste. Benzoic acid, oil of
bitter almonds, benzamid, cinnamic acid, and toluol reappear in the urine as
hippuric acid. The benzoic acid unites with the elements of glycocoll (glycin),
and is excreted as hippuric acid in the urine.

Benzoic Acid. Glycocoll. Hippuric Acid. Water.

C;HA + C.HjNO., = CyHyNOa + HoO.

The amount is increased by eating pears, a])ples with their skins, cranberries,
and plums. Xothing is known of its clinical significance. It seems to be
formed chiefly from the husks or cuticular structures.

Tests and Reactions.

(a.) Heat some crystals in a dry tube. Oily red drops are
deposited in the tube, while a sublimate of benzoic acid and
ammonium benzoate are given off. The latter is decomposed,
giving the odour of ammonia, while there is an aromatic odour of
oil of bitter almonds.

(b.) Examine the colourless four-sided prisms with the micro-
scope (fig. 6g).

('-,) Boil with HNO3, and heat to dryness = odour of nitro-
benzene. Benzoic acid gives a similar reaction.

132

PRACTICAL PHYSIOLOGY.

[xx.

8. Preparation of Hippuric Acid. — (a.) Take loo cc. of cow's
or horse's urine, and evaporate it to one-sixth its bulk ; add hydro-
chloric acid, and set it aside. The brown mass is collected, dried

between folds of blotting-
paper, redissolved in a very
small quantity of water, and
mixed with charcoal, then
filtered and set aside to
crystallise. It is not quite
pure and contains a brownish
colouring-matter.

(b.) Boil horse's urine with milk
of lime = a copious precipitate.
Filter off the bulk of the precipi-
tate through flannel, and filter
again through paper. Concentrate
the filtrate to one-sixth of its volume and add hydrochloric acid = a copious
precipitate of prismatic crystals of hippuric acid. After twenty-four hours
decant the fluid from the crystals, redissolve the latter in hot water, and filter
through animal charcoal.

Fig. 69.— Hippuric Acid.

9. Kreatiniti (C4H-N3O) is related to the kreatin of muscle.

If kreatin be boiled with acids or with water for a long time,

it loses water, and becomes • converted into a strong base —
kraatinin.

Quantity, 0.5 to i gram (7 to 15 grs. ). It is easily soluble in water and
alcohol, and forms colourless oblique rhombic crystals. It unites with acids,
and also with salts, chiefly with ZnClo ; the kreatinin-zinc-chloride is used as
a microscoj)ic test for its presence. It rarely occurs as a deposit, and nothing
is known of its clinical significance.

10, Preparation of Kreatinin.— («.) Take 250 cc. of urine, precipitate it with
milk of lime, and filter. Evaporate the filtrate to a syrupy consistence, and
extract it with alcohol. Filter, and to the filtrate add a drop or two of a
neutral solution of zinc cliloride, and set the vessel aside. After a time
kreatinin-zinc-chloiide (C4H7N3O, ZnCU) is deposited on the sides of the vessel.

(b.) To half a litre of urine add baryta-mixture (p. 124) until no further
precij)itation takes place ; filter, and evaporate the filtrate to a thin syrup on
a water-bath, add to this an equal volume of alcohol, allow it to stand for
twenty-four hours in the cold, whereby the salts are separated, filter, and to
the filtrate add 1-2 cc. of a concentrated alcoholic solution of zinc chloride.
After a time kreatinin-zinc-chloride separates as a yellow crystalline powder.
After two to three days filter, wash with alcohol, and dissolve in M'arm water,
and decom])ose it by boiling for half an hour with hydrated lead oxide
or carbonate of lead. Filter while hot, decolorise the filtrate with animal
charcoal, filter again, eva})orate to dryness, and extract the kreatinin from the
residue with alcohol in tlie cold. A small quantity of kreatinin remains un-
dissolved.

XX.

URIC ACID, ETC.

133

11. Tests and Reactions of Kreatinin.

(a.) JafFe's Test. — Examine the deposit of the zinc compound
microscopically. It forms round brownish balls, with radiating
lines (fig. 70).

(b.) Weyl's Test. — Touriue add a very dilute solution of sodium
nitro-prusside, and very cautiously caustic soda = a ruby-red colour,
which lb evanescent, passing into a straw colour.

{(■.) A solution of kreatinin reduces an alkaline solution oi cupric oxide, cjj.,
Fehling's solution.

Fig. 70. — Kreatinin-Eioc-chloride. a. BaUs with radiating marks ; b. Crystallised
from water ; c. Rarer forms from an alcoh"iic extrait.

12. Colouring-Matters of the Urine. — (1.) Normal Urobilin,
which is the principal colouring matter in normal urine. Add to
urine neutral and basic lead acetate = a precipitate of lead salts,
which carry down with them the colouring matter, leaving the
solution nearly colourless. Filter. Extract tlie pigment from the
filtrate by alcohol acidulated with U.,SO^. Filter = alcoholic extract
of deep yellow colour, which can be extracted by chloroform. On
evaporation of the chloroform it is deposited as a yellow-brown
mass, which in an acid solution, shows with the spectroscope one
absorption band close to and inclosing F at the junction of the
blue and green. On adding an alkali the band disappears
{MarMunn). Its spectrum and composition are practically identical
with choletelin Cj^HjyN.,0.^, and it is regardcnl as an iron-free
derivative of hemoglobin on the supposition that it is modified

134 PRACTICAL PHYSIOLOGY. [XX.

bile-pigment absorbed from the intestinal canal and excreted by
the urine.

<2.) [Febrile Urobilin. — This gives the dark colour to urines in fever. It
seems to be a less oxidised form of urobilin, is isolated in the same way, its
specti'um shows the band near F, and two additional bands, one near D and
one between D and E.]

(3.) Indigo-forming Substance (Indican). — This is derived from iudol,
CjH^N", whicli is developed in the intestinal canal from the pancreatic diges-
tion of proteids, and also from the ]>utrefactiou of albuminous bodies. It may
also be formeil from bilirubin. In urine it is a yellow pigment, and is more
plentiful in the urine of the dog and horse. It exists in the urine as a
conjugated sulpho-acid salt of potassium, viz., as inJoxvl-sulphate of potas-
sium (CgHsNSOjK).

13. General Reactions for Urine Pigments.

{'I.) Add to normal urine a quarter of its volume of HCl, and
boil = a fine pink or yellow colour.

(b.) Add nitric acid = a yellowish-red colour, usually deeper than
the original colour.

(r.) To two volumes of sulphuric acid in a test-tube add one of
urine, but drop the latter from a height. The mixture becomes
more or less garnet-red if indican be present.

(d.) Add acetate of lead = a precipitate of chloride, sulpliate, and
phosphate of lead. Filter ; the filtrate is an almost colourless
solution. This substance is used to decolorise urine for the sac-
charimeter.

(e.) Filter urine through animal charcoal ; the urine will be
decolorised.

(/. ) If po.ssible, obtain a dark-yellow coloured urine, and perform the
following test :- Take 40 drops of urine +- 3 to 4 cc. of strong HCI and 2 to 3
drops of HXO,, ; on lieating, a violet red colour with the formation of true
rhombic crystals of indigo-blue indicates the presence of indican.

{g.) Test for Indican. — Mix equal volumes of urine and HCl, add, drop by
drop, a saturated solution of chloride of lime (/.''., bleaching powder, which
also contains hypochlorite of calcium) = a blue colour. Shake uj) with chloro-
form and the blue colour is absorbed by the latter.

14 Phenol (carbolic acid), C,|H,0. occurs in the urine as phenol-sulphate of
])otassium, C^H^O - SO.j — OK. There is a corresponding salt of Crasol, most
abundant in tlie urine of herbivora. Add sulphuric acid to urine until the
latter contains 5 per cent, of the acid. Distil as long as the distillate becomes
cloudy with bromine water. Test the distillate as follows : —

(a.) Bromine water = precipitate of tri-bromo-phenol (CeH^.Br^OH).

(/;.) Neutralise and add neutral ferric chloride = violet colour.

(c. ) Heated with Millon's reagent it gives a red colour. (See also p. 82. )

The patliolog'cal pigments — bile, blood, &c. — occurring in urine
will be referred to later.

XX.] URIC ACID, ETC. 1 35

15. Mucus, — A trace of nmcns occurs normally in urine. Col-
lect fresh uiine in a tall vessel, and allow it to stand for some
time, when fine clouds (" mucous clouds ") like delicate cotton-
wool appear. These consist of mucus entan<,ding a few epithelial
scales,

(a.) If the urine contain an excess of mucus, on adding a satu-
rated solution of citric acid to form a layer at the bottom of the
test-tube, a haziness at the line of junction of the urine and acid
indicates mucus. There is no deposit with healthy, freshly-passed
urine. Citric acid is used because it is heavier than acetic.

16, Feiments in Urine. — There is no doubt that urine contains
pepsin. Some observers state that it also contains trypsin and a
sugar-forming ferment ; but the latter statement is denied.

(a.) Select the morning urine, place in it for several hours fresh
well-washed and boiled fibrin. The latter absorbs the ferment,
and on placing it in .2 per cent. HCl at 40° C, the pepsin is
dissolved and peptones are formed. Test for the peptones by the
biuret reaction.

17, Reactions of Normal Urine towards Reagents.

(l.) Add 5 cc. of HCI to 100 of urine. After twenty-four hours crystals of
uric acid separate out.

(2.) Add caustic soda or ammonia = j)recij)itate of the phosphates of the
alkaline earths, partly in an amorphous state, partly in acicular crystals.

(3. ) Acidulate with nitric acid and heat with phospho-molybdic acid = blue
coloration due to urates.

(4.) Add mercuric nitrate == white cloudiness, which disappears on shaking.
This is a precipitate due to the formation of sodium nitrate and mercuric
chloride (Hg(N03)2-l-2XaCl =?NaX03 4- HgCl.,), soluble in acid urine. After
all the NaCl is decomposed — but not until then— a permanent precipitate, a
conijiound of urea and the mercury salt, forms.

(5.) Silver nitrate = white precijiitate of AgCl and Ag^PO^ ; the latter falls
first, and afterwards all the silver combines with the chlorine. The precipi-
late is insoluble in HXO3 but soluble in NH4HO.

(6.) Barium chloride = white jnecipitate of BaS04 and Ba.(P0j)2.

(7.) Lead acetate = whitish precipitate of PbS04. PbClo, Pb;,(Pd4).2, and the
pigments.

(S. ) Ferric chloride after acidulation with acetic acid = precii'itate of

(9.) An ammoniacal solution of cupric oxide is decomposed and decolorised
at the boiling-point by the urates.

(10.) Tannic acid = no precipitate (Znttoifte^-gr).

18. Estimation of TJrlc Acid. — This is sometimes doue by the method (2, n),
but it is not accurate, {a. ) Haycraf t s Method depends on the formation of urate
of silver, which is jiractically insoluble in water or acetic ■,>cid{Brihs/t Medical
Jo-urnal, 18^5). The urate of silver is of a slimy nature and must be washed
on an asbestos filter. The titriition of the silvei compound is by means of
Volhard's ammonium thio-cyanate method (Sutton's Volumetric Analysis, 5th
edit., 1886, pp. 116, 324).

136

PRACTICAL PHYSIOLOGY,

[XXL

(b.) Hopkin's Method.— Saturate the fluid with crystals of ammonium
chloride == ammonium urate. Collect the precipitate and dissolve it in weak
alkali. Reprecipitate by HC1 = precipitate of uric acid, which is dried and
weighed.

19. Average Amount of the Several Urinary Constituents Passed in Twenty-
four Hours by a Man Weighing 66 kilos.

Grams.

Water .

.

. 1500

Total solids .

72

Organic solids —

Grams.

fnorganir, solids —

Grams.

Urea

33-18

Sulphuric acid

2.01

Uric acid .

.

•55

Phosphoric acid

3.16

Hippuric acid

.

.40

Chlorine

7.00

Kreatinin

.91

Ammonia

0.77

Pigment and

other sub-

Potassium

2.50

stances .

• • •

10.00

Sodium .
Calcium
Magnesium .

11.09
0.26
0.21

— Farkes.

LESSON XXI.

ABNORMAL CONSTITUENTS OF THE URINE.

Some of the substances referred to in the subsequent lessons are
present in excessively minute traces in normal urine — e.fi , sugar ;
and in the urine of a certain percentage of persons appar-
ently enjoying perfect health, minute traces of albumin are some-
times present. When, however, these substances occur in con-
siderable quantity, then their presence is of the utmost practical and
diagnostic value, and is distinctly abnormal. It is quite certain
that serum-albumin is never found in any considerable amount in
normal urine.

1. Albumin in Urine. — When albumin occurs in notable quantity
in the urine, it gives rise to the condition known as albuminuria.
Albuminous urine is not unfrequently of low s.g., and froths
readily.

Various forms of proteid bodies may occur in the urine. 'J he
chief one is serum-albumin; but, in addition, serum-globulin,
albumose, peptone, acid-albumin, and fibrin may be found.

2, Tests. — In every case the urine must be clear before testing,
which can be secured by careful filtration,

(a.) Coagulation by Heat. — If the urine is acid place 10 cc.

XXI.]

ABNORMAL CONSTITUENTS OF THE URINE. 1 37

of urine in a test-tube and boil. Near the boiling-point, if albumin
be present in small amount, it will give a haziness; if in large
amount, a distinct coagulum. On standing, the coagulum is
deposited. Some prefer to boil the top of a long column of
urine in a test-tube. If the urine be acid, then any haziness
formed is readily seen against the clear .subnatant Huid.

Precautions. — (i. ) Always test the reaction of the urine, for albuniin is only
precijiitated by boiling in a neutral or acid medium. Hence if the urine be
alkaline, bailing will not jn-ecipitate any albumin that may be jn-esent. (ii.)
Boil the ujijier stratum ot the tiuid first of all. holding the tube obliquely,
taking care that the coagulum does not stick to the glass, else the tube is
liable to break, (iii.) Heat, by driving off tbe CO2, also jtrecipitates wo-^Ai/
p/wsp/ia/rs if the}' are jnesent in large amount, hence a tuibidity on boiling
is not sufficient pioof of the presence of albumin. The points of distinction
are, that albumin goes down before the boiling-point is reached (coagulated
at 75" C), while phosphates are ])recipitated at the boiling-point. Again,
the phosj)hatic deposit is soluble in an acid — ''.(f., acetic or nitric— while the
albuminous coagulum is insoluljle in these fluids. Some, therefore, advise
that the test be done in the following manner : —

(A.) Acidulate the urine with a few drops of dilute acetic or
nitric acid, and then boil. If nitric acid be used, add oue-tentli to
one-twentieth of the volume of urine.

Precautions. — If the urine contain only very minute traces of albumin, the
latter may not be ])recipitated if too much nitric acid be added, as the acid
albumin is kept in solution. If too little acid be added, the albumin may not
be precipitated, as only a ])art of the basic jjhosjjhates are changed into acid
phosjihates, and the albumin remains in solution as an albuminate (a com-
pound of the albumin with the basej. On heating the urine of a person who
is taking coj)ail)a, a deposit may be obtained, but its solubility in alcohol at
once distinguishes it from coagulated albumin. This test acts witli serum -
albumin and globulin, and if the deposit occurs only after cooling, also with
albumose, but not with peptone.

(c.) Heller's Cold Nitric Acid Test. — Take a conical test-glass,
and place in it 15 cc. of the urine. Incline it, and pour slowly
down its side strong nitric acid = a white cloud at the line of
junction of the fluids.

Precautions. — A crystfilline dej)Osit of ure;i nitrate is sometimes, though
very rarely, obtained with a very concentrated urine. If the urine contain a
large amount of urates, they may be deposited by the acid, but the deposit in
this case occurs above the line of junction, and disappears on heating. It is
not obtained if the urine be diluted beforehand.

(</.) Acidulate 10 cc. of urine with acetic acid, add one-fifth of its bulk of a
saturated solution of magnesium or sodium sulphate, and boil = a precipitate.

(e.) Acetic Acid and Potassium Ferrocyanide. — Acidify strongly with
acetic acid, and add a solution of pota.ssium ferrocj'anide = a white precipi-
tate, varying in amount with the albumin present. The reaction may be
done as follows : — Mix a few cc. of moderately strong acetic acid with some
solution of potassium ferrocyanide, and })our this over some urine in a test-tube

138 PRACTICAL PHYSIOLOGY. [xXL

by the contact method {(L). The presence of albumin is indicated by a white
deposit in the form of a ring at the line of junction of the Huids. A solution
of platino potassium cyanide may be used instead of the ferrocyanide. The
solution of the former is colourless. This test precipitates serum-albumin,
globulin, albumose, but not peptone.

( /'.) Picric Acid. — Use a saturated watery solution, and apply it
by the contact method of Heller {c). The urine is below, and the
picric acid on the top. A rapidly-formed deposit at the line of
junction of the fluids indicates the presence of a proteid ; the
deposit is not dissolved by heat.

N.B. — Picric acid precipitates all the forms of proteid which occur in urine.
It also precii)itates mucin, but in this case the deposit usually lorms slowly
and after a time. If a person be taking quinine, a haziness is obtained in the
urine on adding piciic acid, but it disappears on heating. Dr. Johnson and
Professor Grainger Stewart recommend it as one of the most reliable tests for
albumin we possess.

(f/. ) Metaphosphoric Acid completely preci])itates albumin, but it must be
fi'eshly prepared, and is difficult to keep. Hence it is not satisfactory.

{h.) Acidulated Brine, as suggested by Roberts, consisting of a saturated
solution of sodium chloride with 5 per cent, of dilute hydrochloric acid (B P. ),
may be used, but it sometimes gives a precipitate with normal urine. Nor is
potassio-mercuric-iodide ss-tisfactory (Taaret.). In cases of doubt, use several
tests, especially 2 {//.), (c), (e.), and (/. ).

(i.) Trichloracetic Acid precipitates albumin in urine.

(/.) Salicyl-Sulphonic Acid gives a white precipitate with proteids, which
is soluble on heating in the case of albumose and peptone {.W K'illiam).

3. Dry Tests.

{a.) Use the ferrocyaiiic pellets introduced by Dr. Pavy.
(/». ) Use the test-papers — citric acid and ferrocyanide of potassium — intro-
duced by Dr. Oliver.

4. Globulinurla. — Serum-globulin is present in nearly every
albuminous urine. It gives the reactions described under 2.

(a.) Fill a tall glass with water. Drop the urine into the water,
and observe if a milkiness is seen in the water, indicating the
presence of a globulin. This body is not soluble in pure water,
but in weak saline solutions (Lesson I. 6), hence on diluting the
urine it is precipitated.

(b.) Test the urine by the contact method with a saturated solu-
tion of magnesic sulphate.

(c.) '1 his body is completely precipitated on saturating the urine
with ammonium sulphate.

If globulin be present along with serum-albumin add an equal
volume of a saturated solution of ammonium sulphate. A white
flocculent precipitate indicates globulin.

XXI. ]

ABNORMAL CONSTITUENTS OF THE URINE.

139

5. Albiimosiir'a. — Hemi-albumose, wliicli, liowever, is really a mixture of
three dilleieiit proteids, has been found in cases of osteomalacia. If such a
urine can be procured, do test 2 {b.), using nitric acid ; tlie deposit only takes
I)lace after a long time or on cooling, and in fact the urine sometimes becomes
almost solid, but is dissolved by heat. If there is a deposit, filter and test the
filtrate for proteid reactions, e.(i., the biuret test. It will give a precipitate
with acetic acid and potassic ferrocyanide. Then saturate a })ortion of the
urine with sodium chloride, and acidify with acetic acid = a {jrecijiitate, which
dissolves on adding much acetic acid and heating, and reappears on cooling
(P- 73)-

6. Peptonuria.^ — Peptone is frequently present in albuminous urine. Pep-
tone is most frequently present in urine in cases where there is an accumula-
tion and breaking up of leucocytes or pus-corj)uscles, as in

the stage of resolution of j)neumonia, sup])urative processes,
and in other diseases. Procure such a urine. It is well to
get rid of the albumin by acidification with acetic acid and
boiling.

(a.) Put some urine in a test-tube, and by the contact
method pour on some Fehling's solution. At the line of
junction a phos{)hatic cloud is formed, and, if peptones be
present, above it a rose-pink colour. If albumin also be pre-
sent, a violet colour is obtained. Hemi-albumose gives the
same reaction.

7. Quantitative Estimation of Albumin. — This can only be
done accurately by precipitating the albumin, drying and
weighing it ; but as this is a tedious process, and requires
much time, it is not suitable for the physician.

8. Esbachs Albnminimeter (fig. 71).

A. The Reagent. — Dissolve 10 grams of picric acid
and 20 grams of citric acid in 800 cc. of boiling water,
and make up the solution to a litre.

Dr. Johnson finds that a solution of picric acid in
boiling water (5 grains to the ounce) gives the same
result.

B. Process. — Pour urine into the tube (6 inch x |
incli) up to the mark U, then the reagent up to the
mark K, mix thorouglily. Set the tube aside for
twenty-four hours, and then read off on the scale the
heiglit of the coagulum. The figures indicate tlie
grams of dried alljumin in a litre of urine — i.e., the
percentage is obtained by dividing by ten. If the

coagulum is above 4, or if the original s.g. of the urine is above
loio, dilute the urine first with one or two volumes of water, and
then multiply the resulting figure by 2 or 3 as the case may be. If
the urine be alkaline, it must first be acidulated by acetic acid.
If the amount of albumin be less than 0.5 grams per litre, it
cannot be accurately estimated by this method.

Fig. 71.

Esbauli's Tube.

140 PRACTICAL PHYSIOLOGY. [XXK.

LESSON XXII.
BLOOD, BILE, AND SUGAR IN URINE.

1. Blood in Urine (Haematuria).

The Blood may come from any part of the urinary apparatus.

If from L'idncij, it is usually small in amount and well mixed with the
mine, and the microscope may reveal the presence of " blood-casts," i.e.,
hlood-moulds of the renal tubules. Large coagula are never found, and the
mine not unfrequently is "smoky." From the lilmUlcr or urcihra, usually
the urine is bright red, and relatively laige coagula are frequently present.
In all forms, bloodcorj)Uscles are to be detected by the microscope, and
albumin by its tests.

(rt.) Examine the naked-eye characters of a specimen. It may
be any tint from red to brown, but if the blood is well mixed with
the urine, the latter usually has a " smoky " appearance.

{h.) Microscope. — Collect any deposit and examine it microscop-
ically for blood-corpuscles, which, however, are frequently dis-
coloured or misshapen.

(c) Spectrum. — Examine for the spectrum of oxy haemoglobin
or met-hfemoglobin (Lesson VI. 6, 1).

{(I.) Guaiacum Test. — Mix some freshly prepared tincture of
guaiacum with urine, and pour on :t some ozonic ether ; a blue
colour indicates the presence of haemoglobin. This reaction may
be done on filter-paper.

[c.) Heller's Blood Test. — Make the nrine strongly alkaline with caustic
soda, and boil. On standing, a deposit of earthy phosphates, coloured red or
brown by lui-niatin, occurs, the deposit carrying down the altered colouring-
matter of the blood with it. This is not a satisfactory test.

(/. ) The urine gives the reactions of albumin.

2. Hsemoglobinuria.

This term is applied to that condition where lisemoglobin is excreted
through the kidney as such, and is not contained within the blood-corpuscles.
Tiie urine contains hi^moglobin, but not the blood-corpuscles as such. It
occurs when blood-corj)Uscles are destroyed within the blood-vessels, as after
the transfusion of the blood of one s{iecies into the blood-vessels of another
species ; after the transfusion of warm water ; the injection of a solution of
li.X'moglobin into a vein ; and after extensive destruction of the skin by burn-
ing. It also occurs in purpura, scurvy, often in typhus or scarlet fever,
pernicious malaria, in "periodic hirmoglobinuria," and after the inhalation
of arseniuretted liydrogen.

('^) The urine gives the same reactions as in haematuria, but no
blood corpuscles are detected by the microscope.

XXII.] BLOOD, BILE, AND SUOAR IN URINF. I4I

3. Bile in Urine, — The biliary constituents appear in the urine
in cases of jaundice and in poisoning with phosphorus. One may
test for the bile-pif/menh; or the bile-acids, or both.

A. Bile-Pigments.

(rt.) Colour. — The urine has usually a yellow or yellowish- green
colour, and it froths very easily when shaken. Filter-paper dipped
into it gives a yellow stain on drying.

(Ij.) Gmelin's Test (Nitric acid containing Nitrous acid). — (i.)
Place a few drops of the suspected lu-ine on a white porcelain plate,
and near it a few drops of the impure nitric acid ; let the fluids run
together and the usual play of colours is observed (Lesson XL 6).
(2.) Take urine in a test-tube, pour in the impure HXO3 until it
forms a stratum at the l^ottom ; if bile-pigments be present, at the
line of junction of the fluids a play of colours takes place — from
above downwards — green, blue, violet or dirty red, and yellow.
Nearly all urines give a play of colours, but f/reen is the necessary
and characteristic coloiu- to prove the presence of bile-pigments.
(3.) Kosenbach's Modification.— Filter the urine several times
througli the same filter, dry the filter-paper, and to it apply the
impure nitric acid, when the same play of colours is observed.

(c.) A solution of methyl-violet poured on icteric urine by the contact
method gives a bright carmine ring at the point of contact.

((/. ) If much bile-pigment be jnesent, the following test succeeds : —Mix
the urine with caustic potash (i KHO to 3 water), and add hydrochloric acid.
The fluid becomes green, due to the formation of biliverdin.

B. Bile-Acids (Glycocholic and Taurocholic acids).

(a.) Pettenkofer's Test.— -Add to urine a few drops of syrup of
cane-sugar (8 per cent.), mix them, and pour strong sulphuric acid
down the side of the tube until it forms a layer at the bottom.
The temperature must not rise above 70° C, nor must the urine
contain albumin. At the line of junction a cherry-ren or jnirple-
violet colour indicates the presence of the bile-acids. Or proceed
as follows : — Shake the tube with the urine and the syrup to get a
froth, and when the sulphuric acid is added the froth shows the
colour. N.B. — The test in this simple form often fails with urine,
and in fact there is no satisfactory simple test for minute quantities
of these acids in urine.

(/). ) Strasburger's Modification. — Dissolve cane-sugar in the suspected
urine, dip into it filter-paper, and allow this to dry. Touch the pa])er with a
glass rod dipped in strong sulphuric acid, a purple-violet colour indicates the
presence of the bile-pigments.

(c.) Sulphur Test.— Try this (Lesson XI. 5).

4. Sugar in Urine (Glycosuria). — Briicke maintains that the
merest trace of (jlncose or r/rape-suyar is normally present in urine.

142 PRACTICAL PHYSIOLOGY. [XXIL

In diabetes mellitus, liowever, it occurs in considerable amount, and
is, of course, then quite abnormal.

Characters of Diabetic Urine.

(i.) The patient iisuallj'^ passes a very large quantity of urine,
even to 10,000 cc, and although the quantity of fluid is large

(2.) The specifii: gravity is high — 1030 to 1045 — due to the
presence of the grape-sugar. N.B. — AVhen the quantity of lU'ine
is above normal, and the specific gravity reaches 1030, suspect the
presence of grape-sugar.

(3.) The colour is usually a very pale straw, from the dilution —
not diminution — of the urine pigments. The urine is often some-
what turbid,

(4.) It has a heavy sweet smell, and usually froths when poured
from one vessel into another.

5. Tests for Grape Sugar.— In all cases remove any albumin
present, i.e., acidulate with acetic acid, boil, and filter,

{a. ) Moore's Test. — To urine add an equal volume of caustic soda or potash,
and boil the upj)er stratum of the fluid. If much sugar be present, a dark
sherry or bistre-luown colour is obtained. The colour may vary from a light
yellow to a dark brown (due to the formation of glucic and melassic acids),
according to the amount of sugar present. This is not a delicate test.

{h.) Trommer's Test. — Add to the urine one-third its bulk of
caustic soda solution, and then a feiv drops of a solution of cupric
sulphate, and a clear blue solution of the hydrated oxide is
obtained. Boil the upper stratum of the fluid. If sugar be
present, a yellow or yellowish-red ring of reduced cuprous oxide
is obtained

{r.) Fehling's Solution is alkaline potassio-tartrate of copper
(K^CuaC^H^Og). Place some Fehhng's solution in a test-tube and
boil it. If no discoloration (yellow) takes place, it is in good con-
ilition. Add a few drops of the suspected urine and boil, when
the mixture suddenly turns to an opaque yellow or red colour,
which indicates the presence of a reducing sugar.

{d.) Bottgrer's Test. — Mix the urine with an equal volume of sodium
carbonate solution, add a little basic bismuth nitrate, and boil for a short
time. A grey or black depo.sit indicates the i)reseiice of a reducing sugar.

(e.) Picric Acid. —To the urine add an equal volume of a saturated watery
solution of picric acid, and then caustic potash. Boil, an intensely deep red
or reddish-brown colour indicates the jiresence of a reducing sugar. The
larger the amount of sugar, the deeper the tint. The colouration is due to
the formation of })icramic acid.

(/.) Phenyl-Hydrazin, — Eepeat this as described in Lesson III.
This is a reliable test.

XXIII.] QUANTITATIVE ESTIMATIf)N OF SUGAR. 143

{(J.) Indigo-Carmine Test.— To the urine add sodium carbonate solution and
indigo-carmine solution until a blue colour apjiears. Boil, and a yellow colour
is obtained, if sugar be jiresent, owing to the reduction of indigo-blue to indigo-
wliite Pour the fluid into a cold te.st-tube, when the blue colour is restored,
a beautiful play of colours intervening between the yellow and the blue. This
is not a satisfactory test.

(/(.) Repeat Molisch's test (Lesson I.).

6. Preparation of Fehling's Solution. — Solution A. 34.64 grams of pure
crystalline cupric sulphate are powdered and dissolved in 500 cc. of distilled
water. 6olt'tioa B. In another vessel dissolve 173 grams of Rochelle salts
vsodio-potassium tartrate) in 100 cc. of pure caustic soda, sp. gr. 1.34, and add
water to make 500 cc. Keep the two solutions separate in stoppered bottles,
and mix them as re<|uired. On mixing equal quantities of A and B. a clear deep
blue fluid is obtained, the Rochelle salt holding the cupric hydrate in solution.

X.B.— Fehling's solution ouglit not to be ke[it too long ; it is apt to decom-
pose, and should therefore be kept away from the light, or protected with
opaque paper pasted on the bottle. Some other substances in urine — e.g., uric
and glycuronic acids— reduce cupric oxide. In all cases see l/icU there is an
excess of the test present.

LESSON XXIII.
QUANTITATIVE ESTIMATION OF SUGAR.

1. By the Saccharimeter,

Study the use of some form of saccharimeter. The portable form made by
Zeiss is very convenient A coloured urine must first be decolorised by acetate
of lead [Lesson XX. 13 ('^.)].

2. Diabetic Urine. Volumetric Analysis by Fehling's Solution.
— 10 cc. of Fehling's solution = .05 gram of sugar.

(a.) Ascertain the quantity passed in twenty-four hours.

{h.) Filter the urine, and remove any albumin present by boihng
and filtration.

(c.) Dilute 10 cc. of Fehhng's solution with about five to ten
times its volume of distiUed water, and place it in a white porcelain
capsule on a wire gauze support under a burette. [It is diluted
because any change of colour is more easily observed.]

{d.) Take 5 cc. of the diabetic urine, add 45 cc. of distilled
water, and place the diluteil urine in a burette. Diabetic urine
usually contains 4 p.c. or more of dextrose, and as the solution to
be tested should not contain more than 0.5 p c. of dextrose, hence
the necessity for diluting the urine.

(1".) Boil the diluted Fehling's solution, and whilst it is boiling
gradually add the diluted urine from the burette until all the
cuprous oxide is precipitated as a reddish powder, and the super-

144

PRACTtCAL PHYSIOLOGY.

[XXITT.

natant fluid lias a straw-yellow colour, not a trace of blue remain-
ing. This is best seen when the capsule is tilted. It is i\ot
advisable to sjDend too much time in determining when the blue
colour disappears, as it is apt to return on cooling. It is sometimes
difficult to determine when all the blue colour has disappeared.
Tlie following jirocess is useful. Filter a little
of the hot fluid, acidulate with acetic acid and
add potassic ferrocyanide. If copper is present
a brown colour or precipitation is produced. If
this be so, add more urine until no brown colour
is produced.

[Pavy's modification of Feliling's solution is sometimes
iised. In it ammonia holds the copper in solution, so
that there is no yellow or red jjrecipitate formed, as the
ammonia holds the oxide in solution. The reduction
is comj)lete when the blue colour disapj)ears. lo cc.
Pavy's Fehling=i cc. Pehling = 5 milligrams of dex-
trose. ]

(/.) Eead off the number of cc. of dilate
urine employed. If i8 cc. were used, this, of
course, would represent 1.8 cc. of the original
urine.

(f/.) Make a second determination, using the
data of the first, and in this case run in at once
a little less of the dilute urine than was required
at first.

Example.— Suppose the patient passes 8550
cc. of urine, then as 1.8 cc. of mine reduced all
the cupric oxide in the 10 cc. of Feliling's solu-
tion, it must contain 0.5 gram sugar; hence

8550 : : .05.-.

Ficj.

I'icro-Sac-
chaiiiiieter.

85.SOX-05 =
1.8

237-5 gi'anis of

sugar passed in twenty -four hours.

3. Picro-Saccharimeter of G. Johnson.

Solutions Required.

(i.) A solution of ferric acetate the colour of which is equal to that yielded
by a solution of sugar containing \ grain per lluid ounce.

(2.) Saturated solution of picric acid.

(3.) Liquor potassii' (B. P.).

{a.) Measure i fluid draclun of urine into the boiling tube, add 30 minims
of liquor potassre and 80 minims of the saturated .solution of picric acid.
Make up to the 4-drachm mark on the tube with distilled water. Boil for
one minute.

XXIII.] QUANTITATIVE ESTIMATION OF SUGAR.

U5

{b.) Dip the tube in cold water to cool it. The volume must be exactly 4
drachms. If it is less, add water ; if more, evajwrate it. If the colour of the
boiled liquid is the same as that of the ferric acetate ^-grain standard, or
paler, the urine contains i grain of sugar per Huid ounce, or less.

(f.) Should the colour be darker than the standard, place some of the boiled
liquid in the graduated stop])ered tube (fig. 72) to fill ten divisions of the
scale, while the stoppered tube affixed to the former is filled with the SS. of
ferric acetate. Fill up the graduated tube with distilled water until the dark
red liquid has the same colour as that of the SS. These tints are best compared
in the Hat-bottomed tubes supplied with the apj)aratus.

{d.) Read ofi' the level of tlie lluid in the saccharimeter, each division
above 10 = 0.1 grain per fluid oz. Thus, 13 divisions = .3 grains per fluid oz.

(e.) If more than S grains per oz. are present, further dilution is required.
Full instructions are supplied with the apparatus.

4. Fermentation Method. — Sir William Roberts has devised a method
depending on the diminution of the specific gravity which the fluid undergoes
during fermentation. Every degree lost in the sp. gr. corresponds to i
grain of sugar in a fluid ounce. Recently a modification of this method has
been introduced in Germany under the title of Einhorn's Fermentation
Saccharometer (fig. 73). Estimate the specific gravity of the urine, which is
diluted according to the specific gravity as follows. If the urine have a

Sp. gr. 1018-1022, dilute it with 2 vols, water.
„ 1022-1028, „ „ 5 „
1028-10^8 10 ,,

Measure 10 cc. of the urine, and, by means of a pipette, place it in the appa-
ratus. Add I gram of yeast to the urine in the tube, incline the latter until
the fluid flows into the limb of the latter. Let
the a})paratus stand at the ordinary temperature
for fifteen hours, and then the quantity of CO2
given off" is read off. The scale on the tube is
empirical, and indicates directly the percentage of
sugar in the urine.

5. Acme Sacchar-Ureameter (fig. 74). — This is
a simple apparatus for the direct estimation of sugar
and urea in urine ; the former by the fermentation
test, the latter by the hypobromite.

Estimation of Sugar.— Measure i volume of the
urine in the tube so marked, and pour it into the
bottle a. Wash out with water, and add to the
urine. Dilute further with water if the urine
contains much sugar. Acidify the urine with
tartaric acid until acid to test-paper (5-1 per cent.
of free acid). Add a few grains of yeast, and
connect up the apparatus. The measuring-tube b
is filled to zero with a saturated solution of common
salt (the CO^, is soluble in water). When b is
full, c must be empty. Place the whole in a

moderately warm place — the surrounding temperature should be such as to
enable it to rise to 92°-94° F. When the fermentation ceases — or from time
to time during the time of fermentation — lower c until the levels of brine are
equal. Allow it to cool, and read off the result.

Fig. 73. — Einhorn's Fermen-
tation Saccharometer.

146

PRACTICAL PHYSIOLOGY.

[XXIIL

6. Aceto-Acetic Acid is found in certain diabetic urines, but not in all.

(a.) To the urine add ferric chloride ; a red colour is obtained if this acid

be present. If there is a
deposit of phosphates, filter.
The colour disappears on
heating.

If a diabetic urine con-
taining aceto-acetic acid be
distilled, this acid is de-
composed, and aceton is
obtained,

7. Tests for Aceton
(CsHgO).— To obtain the
aceton, acidulate half a
litre of urine with HCl.
The distillate will give the
following reactions : —

(a.) Lieben's Test— To
a weak, watery solution of
aceton add solution of iodine
dissolved with the aid of
potassic iodide, and then
caustic soda. A yellow
precipitate of iodoform is
obtained. The precipitate
is generally described as
forniiiig hexagonal plates or
radiate stars, but I have
generally found it to be
amorphous or granular.
Other substances give the
iodoform reaction.

(b.) Smell the peculiar
ethereal odour of aceton.

(c.) Legal's Test.— Add
caustic soda solution, and
then a solution of freshly-
prepared sodium nitro-
^= prusside and acetic acid = a
' red colour.

In all cases employ both
tests, but they only give a
decided reaction in urine
when the aceton is in con-
siderable amount. To be
quite certain that aceton is present, a considerable amount of the urine
must be distilled, and the tests applied to the distillate.

8. Tests for Phenol. — The metliod of obtaining phenol from its compound
in the urine is given at p. 134. To a watery solution of phenol —

(a.) Add ferric chloride = a blui.sh-violet colour.

(b.) Add bromine water = a yellow (or rather white) precipitate of bromine
compounds.

(c.) Add Millon's reagent = a beautiful red colour or deposit. This reaction
is aided by heat.

Fig. 74. — Sacchar-T'reameter, made by Messrs. Gibbs,
Cu.\son & Co., Weduesbury.

XXIV.] URINARY DEPOSITS, ETC. 1 47

9. PjrrocatecMn is sometimes found in urine. The method of obtaining it
requires too much time to be done in this course.

Tests.

(a.) To a dilute solution add ferric chloride = a yrcen colour, which becomes
violet on the addition of sodic bicarbonate.

[h.) Add ammonia and silver nitrate, which give a black precipitate of
reduced silver.

LESSOR XXIV.

URINARY DEPOSITS— CALCULI AND GENERAL
EXAMINATION OF THE URINE.

1. Mode of Collecting Urinary Deposits. — (i.) Place the urine in
a conical glass, cover it, and allow it to stand for twelve hours.
Note the reaction before and after standing. With a pipette
remove some of the deposit and examine it microscopically.

(ii.) Dr. Harris has published the folloAving {Brit. Med. Jour.,
1894, vol, i. p. 1356) : — The urine is placed in a tube draAvn to a
fine point, and fixed in a vertical position in a clamp. The pointed
end is down, and after being filled it is corked tight. After the
deposit sul)sides and collects in the lower pointed end of the tube,
a small quantity of it may be obtained by clasping the tube with
the warm hand or by pushing in the cork slightly.

(iii.) Centrifuge.— By means of a small hand centrifuge (fig. 75,
reduced to i), as made by Muencke of Berlin, any deposit in urine
is readily collected at the bottom of a test-tube. The disc I, bear-
ing the tubes G, can be made to rotate 3000 to 5000 times per
minute. Fig. II. sliows the disc in full rotation, and III. the form
of glass vessel used.

There are two classes of deposits, orijanlned and imonianised.

ORGANISED DEPOSITS.

1. Pus fp. 147).

2. Blood (ji. 140).

3. Epithelium.

4. Renal tu])e casts.

5. Sjtermatozoa.

6. ^licro-organisms.

7. Elements ol' morbid growths

and entozoa.

2. Pus in Urine (Pyuria) produces a thick creamy yellowish-white sedi-
ment after standing, although its apjiearancc varies with the reaction ot the
urine. If the urine be acid, the precipitate is loose, and the ])Us-corpusclcs
discrete ; if alkaline,, and es])ecially from ammonia, it forms a thick, tough,
glairy mass. The urine is usually alkaline, and is always albuminous, and
rapidly undergoes dccomjiosition. Pus is found in the urine in Icucorrhaa
in the' female, gonorrhfta, gleet, cystitis, pyelitis, from bursting of an abscess
into any part of the urinary tract, &c.

148

PRACTICAL PHYSIOLOGY.

[XXIV.

(«.) Donne's Test. — Filter off the fluid, and add to the deposit a small
piece of caustic potash, or a few drops of strong solution of caustic potash ;
the deposit becomes ropy and gelatinous, and cannot be dropped from one
vessel into another — due to the formation of alkali-albumin ; the dejiosit is
pus. The same reagent with mw.ns causes the deposit to become more fluid
and limpid, to clear up, and look like unboiled white of egg,

X.

Fig. 75. — Hand Centrifuge made by Muencke, Luisen Stiasse, 58, IJeilin, N.W.
Cost, £^, 10/.

{h.) With the microscope numerous pus-corpuscles are seen, which, when
acted on by acetic acid, show a bi- or tri-partite nucleus. This test is not
absolutely conclusive.

('".) Urine containing pus gives the reactions for albumin, while, if mucus
iloue be present, it gives only those for mucin.

XXIV.]

URINARY DEPOSITS, ETC.

149

UNORGANISED DEPOSITS.

A. In Acid Urin'e.

1. Amorphous.

{a. ) Urates. — Soluble when heated,
redeposited in the cold ; when hydro-
chloric acid is added microscopic crys-
tals of uric acid are formed = urates.

{b.) Tiibasic Phosphate of Lime.
— Not dissolved by heat, but disap-
pears without effervescence on adding
acetic acid. It is probably tribasic
phosphate of lime (Ca32P04).

(c. ) Oil Globules. — Very small
highly refractive globules, soluble in
ether (very rare).

2. Crystalline.

{a. ) Uric Acid. — Recognised by the
shape and colour of the crystals and
their solubility in KHO.

{h.) Oxalate of Lime.— Octahedral
crystals, insoluble in acetic acid (fig.
76).

(f. ) Cystin (very rare). — Hexagonal
crystals, soluble in NH^HO (fig. 78).

(rf.) Leticin and
rare). (Fig. 79.)

(c.) Cholesterin (very rare)
40.)

Tyrosin (very
(Fig.

3. Urinary Calculi.

B. In Alkalink Urine.
I. Amorphous,
(a.) Tribasic Phosphate of Lime
dissolves in acids without eHerves-

(?>.) Carbonate of Lime,
below.)

(See (<:.)

2. Crystalline.

(a.) Triple Phosphate. — Shape of
the crystals (knife-rest or coffin-lid),
soluble in acids.

{b. ) Acid Ammonium Urate. —
Small dark balls, often covered with
si)ines. and also amorphous granules
(lig. 77).

(c. ) Carbonate of Lime. — Small
colourless balls, often joined to each
other ; etiervescence on adding acids
(microscope).

{d.) Crystalline Phosphate of
L^me.

(e.) Leucin and Tyrosin (very rare).

(Fig. 79-)

They are composed of urinary constituents which form urinary deposits,
and may consist of one substance or of several, which are usually deposited in

0

^

FlO. 76— Oxalate of Lime. Octa-
hedra and Hour-glass forms.

Fig. 77. —Acid Urate of Ammonium.

layers, in which case the most central part is spoken of as the "nucleus."
The nucleus not unfrequently consists of some colloid substance— mucus, a

ISO

PRACTICAL PHYSIOLOGY.

[XXIV.

^A

©

v-y

C:

portion of blood-clot, or some albuminoid matter— in wbich crystals of oxalate
of lime or globular urates become entangled. Layer after layer is then de-
posited. In certain cases the nucleus may con-
sist of a foreign body introduced from without.
Calculi are sometimes classified as primary and
srrjindary ; the former are due to some general
alteration in the composition of the urine, whilst
the latter are due to ammoniacal decomposition
of the urine, resulting in the precipitation of
Q phosphates on stones already formed. This of
course has an important bearing on the treat-
ment of calculous disorders. Calculi occur in
acid and alkaline urine. A highly acid urine
favours the formation of uric acid calculi, because
that substance is most insoluble in very acid
urine. A highly alkaline urine favours the for-
mation of calculi consisting of calcinm phosphate or triple phosphide, as these
substances are insoluble in alkaline urine.

0
0

0

Fig. 78.— Cystin.

4. Method of Examining a Calculus.

{a.) Make a section in order to see if it consists of one or more
substances ; examine it with the naked eye, and a portion micro-
scopically.

(/>.) Scrape off a httle, and heat it to redness on platinum foil
over a Bunsen- burner.

Fig. 79. — a.a. Leucin balls ; 6.6. Tyrosin sheaves ; «. Double balls of
ammunium urate.

(A.) If it be entirely combustible, or almost so, it may consist of
uric acid or urate of ammonium, xanthin, cystin, coagulated fibrin
or blood, or ureostealith.

XXIV.] URINARY DEPOSITS, ETC. 15I

(B.) If incombustible, or if it leaves viuch ash, it may consist of
urates with a fixed base (Na, Mg, Ca), oxalate, carbonate, or
phosphate of lime, or triple phosphate.

5, A. Combustible. — Of this group, uric acid and urate of
ammonium give the vmrfxide test.

(i.) Uric Acid is by far the most common form, and constitutes
five-sixths of all renal concretions. Concretions the size of a
split-pea, or smaller, may be discharged as (jrnvel. "When retained
in the bladder, they are usually spheroidal, elliptical, and some-
Avhat flattened ; are tolerably hard ; the surface may be smooth
or studded with line tubercules ; the colour may be yellowish,
reddish, reddish-brown, or very nearly white. AYhen cut and
polished, they usually exhibit a concentric arrangement of layers.
Not unfrequently a uric acid calculus is covered with a layer of
phosphates, and some calculi consist of alternate layers of uric
acid and oxalate of lime. Its chemical relatione : nearly insoluble
in boiling water ; soluble in KHO, from which acetic acid preci-
pitates uric acid crystals (microscopic) ; gives the murexide test
(Lesson XX. 3).

(ii.) Urate of Ammonium Calculi are very rare, and occur
chiefly in the kidneys of children ; they form small irregular, soft,
fawn-coloured masses, easily soluble in hot water.

(iii.) If the calculus is combustible and gives no murexide test,
it may consist of xanthin, which is very rare, and of no practical
importance.

(iv.) Cystin is very rare, has a smooth surface, dull yellow
colour, w^hich becomes greenish on exposure to the air ; and a
glistening fracture with a peculiar soapy feeling to the fingers ;
soft, and can be scratched with the nail. It occurs sometimes in
several members of the same family. It is soluble in ammonia
and after evaporation it forms regular microscopic hexagonal
plates (fig. 78).

The other calculi of this group are very rare.

6. (A.) Group. — A2^ply the Murexide Test.

It is f Treat the original powder with \ No odour = Uric acid.
obtained \ potash. J Odour of !N H;j = Ammonium urate.

The residue is not coloured, hut becomes yellowish-red | x- ,1. •

on adding caustic potash . . . . . }
The residue is not coloured either by KHO or KH4HO ; 1

the original substance is soluble in ammonia, and > = Cj/stin.

on evaporation yields hexagonal crystals . . )
On heating, it gives an odour of burned feathers ; the \

substance is soluble in KHO, and is precipitated ^-^Proteid.

therefrom by excess of HNOa . . . .J

152 PRACTICAL PHYSIOLOGY. [XXIV.

7. B. Incombustible.

(i.) Urates (Na, Ca, Mg), are rarely met with as the sole con-
stituent. They give the murexide test.

(ii.) Oxalate of Lime or mulberry calculi, so called because
their surface is usually tuberculated or Avarty ; they are hard,
dark-brown, or black. These calculi, from their shape, cause
great irritation of the urinary mucous membrane. "When in the
form of gravel, the concretions are usually smooth, variable in
size, pale-grey in colour. Layers of oxalate of lime frequently
alternate with uric acid. When heated it blackens, but does not
fuse, and then becomes white, being converted into the carbonate
and oxide. The white mass is alkaline to test-paper, and when
treated with HCl, it effervesces (COg). Oxalate of lime is not
dissolved by acetic acid.

(iii.) Carbonate of Lime. — Rare in man; when met with, they
usually occur in large numbers. Dissolve with effervescence in
HCI. Sometimes crystals occur as a deposit. They are common
in the horse's urine.

(iv.) Basic Phosphate of Lime Calculi are very rare, and are
white and chalky.

(v.) Mixed Phosphates (Fusible Calculus) consist of triple-
phosphate and basic phosphate of lime. They indicate that the
urine has been ammoniacal for some time, owing to decomposi-
tion of the lu'ea. They are usually of considerable size, and
whitish ; the consistence varies. When triple-phosphate is most
abundant, they are soft and porous, but when the phosphate of
hme is in excess, they are harder. A ichitish deposit of phos-
phates is frequently found coating other calculi. This occurs
when the urine becomes ammoniacal, hence in such cases regard
must always be had to the condition of the urinary mucous
membrane. Such calculi are incombustible, but, when exposed to
a strong heat, fuse into a white enamel-like mass, hence the name,
fusible calculi,

8. (B.) Group.

(i.) 27ie substance gives the murexide reaction, indicates urates.

The residue is treated with water.

It is soluble, and ( Neutralise ; add platinic chloride, a yel- \ _ t> , „ •

the solution is ^ low precipitate J

alkaline . .( The residue yields a yellow flame . = Sodium.

( Ammonium oxalate gives a white crys- \ _p j ■

Scarcely soluble ; I talline precipitate . . . . f "
tlie solution is Ammonium oxalate gives no precipitate, '
scarcely alka- < but on adding ammonium chloride,
line ; soluble in sodic phosphate, and ammonia, there ^ == Magnesium.
acetic acid . is a crystalline precipitate of triple-
L phosphate

XXIV.] URINARY DEPOSITS, ETC. 153

(ii.) The original substance does not give the murexide test.

Treat tlic original substance with hydrochloric acid.

^, ,. , .^, „ ( Caldum carbonate.

It dissolves with effervescence .... ^ \ Magnesium carb.

,. J. 1 cit dissolves with effervescence . . = Calciuin oxalate.

It dissolves ,Tj. _„„i4.„ \

without ef-
fervescence.
Heat the
original sub-
stance, and
treat it with
HCl .

f It melts. \i7'„.i ^oc~k

j The origi- I NH. 1 = Triple phosphate.

There is no jf^^'J^^ T 1°/^'' ''''X ^Ncut.calc.phosp.
effervsce. ^i^j, kHO j ^^^ ' " -'
Heat ma

capsule

It does not^
m e 1 1 o n J- . . . = Acid calc. pihosp.
heating . j

9. General Examination of the Urine,

(i.) Quantity in twenty-four hours (normal 50 oz., or 1500 cc).

(ii.) Colour, Odour, and Transparency (if bile or blood be sus-
pected, test for them).

(iii.) Specific Gravity of the mixed urine (if above 1030, test for
sugar).

(iv.) Reaction (normally slightly acid ; if alkaline, is the alkali
volatile or fixed 1).

(v.) Heat.

(a.) If a turbid urine becomes clear = urates.

(h.) If it becomes turbid = earthy phosphates or alhwnin.
Albumin is precipitated before the boiling-point is reached (73°
C), whilst phosphates are thrown down about the boiling-point.
It is necessary, however, to add HNO^, which Avill dissolve the
phosphates, but not the albumin. A case may occur where both
urates and albumin are present ; on carefully heating, the urine
will first become clear (urates), and then turbid, which turbidity
will not disappear on adding HNO3 (albumin). Estimate approxi-
mately the amount of albumin present.

(vi.) Test for Chlorides, with HNO3 and AgNOg (if albumin be
present, it must be removed by boiling and filtration).

(vii.) If sugar be suspected, test for sugar (Moore's, Trommer's,
or Fehling's test), and if albumin be present, remove it.

(vih.) Make naked-eye, microscopic, and chemical examinations
of the sediment.

154 PRACTICAL PHYSIOLOGY. [XXIV.

APPENDIX.

Exercises on the Foregoing.

A. The student must practise the analysis of fluids containing
one or more of the substances referred to in the foregoing
Lessons,

No hard and fast rule can be laid down for the examination of
the fluids met with in physiological work at all comparable with the
method employed in inorganic chemistry. To begin with, the
student must be largely guided by the physical characters, — colour,
smell, taste, etc. — of the fluid he is dealing with, and these will
usually give him a satisfactory clue as to the chemical tests he
should employ.

N.B. — In all cases concentrate some of the fluid for subsequent
use if required, and complete the concentration on a water-bath to
avoid overheating or charring.

A colourless solution should be examined for proteids and carbo-
hydrates by the method described in Lesson IV., p. 32. Marked
opalescence will indicate milk or glycogen, less distinct opalescence
may suggest the presence of starch or certain proteids. Colourless
solutions may also contain urea, bile-salts, leucin, tyrosin or fer-
ments.

Colour :— A red colour will suggest blood, a r/reen tint bile, a
yellow urine, a hroivn methaemoglobin or hsematin. If blood-
pigment or one of its derivatives is suspected, use the spectroscope
at once, and observe the spectrum of (a) the original solution, {b)
the same shaken with air, and (c) after the addition of (NH4).,S.

The smell may give an indication as to the presence of bile or
urine. Do chemical tests accordingly.

Taste .-—If salt, examine for globulins or urea, if hitter for bile-
salts, if sweet for sugars.

Following the indications obtained from the physical characters,
select from the following chemical tests those applicable to the
fluid which is being examined.

1. Test for proteids by xanthoproteic and Millon's tests, and for
carbohydrates by iodine and Trommer's test. The tests for special
proteids and carbohydrates have been already described (p. 32).

2. Blood : — Test chemically for proteid constituents.

3. Bile : — Do Gmelin's test for bile-pigments, and, if proteids
are absent, Pettenkofer's test for bile-acids. If proteids (not pro-
teoses and peptones) are present, neutralise, boil, filter, and test
filtrate for bile-salts. Remove proteoses and peptones, if present,
by precipitation with alcohol, filter and test filtrate for bile-salts.

XXIV.] URINARY DEPOSITS, ETC. 155

4. Tyrosin : — Add ]\Iillon's reagent and boil. A red colour in
the solution indicates the presence of tyrosin,

5. 67va.-— (i.) Add sodium hypobromite or impure nitric acid
(containing HJN'02). If no bubbles of gas, no urea is present. Jf
gas given off (2.) remove phosphates and sulphates by addition of
baryta mixture and filtration, and remove proteids (see 3.), concen-
trate the filtrate if necessary, place a drop on each of two slides,
allow one to evaporate slowly under a cover-glass, and to the other
add a drop of strong pure HXO3 and cover. Examine the former
for crystals of urea, and the latter for crystals of urea nitrate. For
other tests see Lesson XVIII., p. 119).

6. Uric arid : — If in solution, is in the condition of a urate,
(i.) Add a drop of HCl and allow to stand for 24 hours. Examine
deposit for crystals of uric acid. (2.) Concentrate original solution
(after removal of any proteids present), and apply the murexide
test to a small quantitj6»

7. Kreatinin : — Add a drop of dilute solution of nitroprusside
of sodium and excess of caustic soda. A burgundy-red colour
indicates kreatinin.

8. Ferments :-^{a.) Dif/efitice ferments. — Place 5 cc. of the sus-
pected fluid in each of four test-tubes. Label these A, B, C, and D.
Neutralise the fluid in C and D, if necessary. To A add 5 cc.
.4 per cent. HCl and a thread of boiled fibrin, to B 5 cc. of 2 per
cent, sodium carbonate solution and a thread of boiled fibrin, to C
5 cc. starcli solution, and to D 5 or 10 cc. milk. Place the four
tubes, along with four control tubes A', B', C, D' (the contents of
which are the same as those of A, B, C, and D, but without the
suspected solution) on a water-bath at 40° C. After a time (10 to
30 mins.) examine the tubes. Digestion in A, B, or C, or coagula-
tion of the milk in D, indicates, if there is no corresponding change
in the control tube, the presence, of pe^isiii, trtjpdn, umylolytic
ferment or rennin respectively.

(/'.) Blood ferment. — If the solution is suspected to be salted
plasma, or if it be oxalate plasma, in the former case dilute Avith
water and place in a water-bath. (Lesson V. 21.) In the latter
add calcium chloride (Lesson V. 14), and observe if coagulation
occurs. This will also shoAv presence of fibrinogen.

N.B. — In all cases make a note of what you do, the result
thereof, and your inferences. The following form is convenient : —

Experiment. \ Observation. \ Infei'ence.

156 PRACTICAL PHYSIOLOGY. [XXIV.

B. Examination of Solid substances.
Physical characters.

1. Tho colour may suggest blood-pigment, or one of its deriva-
tives, or bile-pigment.

2. Taste may indicate bile-salts, urea, or sugar.

3. Examine microscopically to see whether amorphous or
crystalline. If the latter, the substance may be recognised by its
crystalline form, e.g., urea, uric acid, urates, leucin, tyrosin, clioles-
terin, &c.

4. Burn some in a tube ; smell it to detect any odour. Observe
if it leaves an ash.

5. Examine its solubility in cold and warm water, caustic soda,
dilute acid, saline solutions, alcohol and ether. Test the solution
in the first four reagents as directed under examination of fluids.
Examine the ethereal solution for fats and cholesterin.

Cholesterin : — (i.) Evaporate a little of the ethereal solution in
a watch-glass, and add a drop of strong HgSO^. A red colour
indicates cholesterin. (2.) Examine microscopically. Cholesterin
crystallises from ethereal solution in colourless needles, from solu-
tion in boiling alcohol in its characteristic plates.

C. Analysis of Urine. — The student must also practise the
analysis of urines containing one or more abnormal constituents,
and he must alwo practise the estimation of the quantity of the
more important substances present. Both sets of processes must be
done over and over again, in order that he may perfect himself in
the methods in common use.

PART II.— EXPERIMENTAL PHYSIOLOGY.

Instruments, &c., to be provided by each Student. — Before
beginning the experimental part of the course, each student
must 2)rovide himself i nth the following : — A large arul a small
pair of scissors ; a large and a fine pointed pair of forceps ;
a small scalpel ; a blunt needle or " seeker " in a handle ;
pins ; fine silk thread ; ivatch-glasses ; narroio glass rod drawn
out at one end to act as a " seeker " ; two camel' s-hair brushes
of medium size. It is convenient to ham them all arranged in
a small case.

PHYSIOLOGY OF MUSCLE AND NERVE.

LESSON XXV.

GALVANIC BATTERIES AND GALVANOSCOPE.

— ^UUUUUU

1. Darnell's Cell consi.sts of a glazed eartliemvare pot with a
liandle (tig. 80), and containing a saturated
solution of copper sulpliate. Crystals of copp(!r
sulphate are placed in it to keep the solution
saturated. The pot is about 18 cm. high, and
9 cm. in diameter. In the copper solution is
placed a roll of sheet-co])per, provided with a
binding screw. "Within is a porous unglazed
cylindrical cell containing 10 p.c. solution of
sulphuric acid. A well amalgamated rod of
zinc, provided at its free end with a bind-
ing screw, is immersed in the acid. The zinc
is the negative pole or Cathode ( - ), and the copper the positive
pole or Anode ( + ).

158

PRACTICAL PHYSIOLOGY,

[xxv.

2. Wilke's Pole-Reagent Paper. — This is a convenient method for deter-
mining the ( - ) pole in any combination. Moisten one of the papers, place it
on a clean piece of glass, and touch the surface with the two wires coming
from the battery ; a red spot indicates the negative pole.

3. Amalgamation of the Zinc. — (a.) The zinc should always
be well amalgamated. When a cell hisses the zinc requires to
be amalgamated. Dip the zinc in lo p.c. sulphuric acid until
effervescence commences. Lift it out and place it on a shallow
porcelain plate. Pour some mercury on the zinc, and with a
piece of cloth rub the mercury well over the zinc. Dip the zinc
in the acid again, and then scrub the surface with a rag under a
stream of water from the tap. Collect all the surplus mercury
and place it in the bottle labelled "Amalgamation Mixture."
Take care that none of the mercury gets into the soil-pipe. A

very convenient method is to
"^ dip the zinc into a thick-walled

glass tube containing mercury
and sulphuric acid. For con-
venience the tube is fixed in a
block of wood.

(b.) The following is another con-
venient "Amalgamation Mixture":
— Witli the aid of gentle heat dissolve
4 ])arts of mercury in 5 parts of
nitric acid and 15 parts of hydro-
chloric acid, and then add 20 parts
of hydrochloric acid. The zincs, after
being well cleaned, as directed above,
are dipped into this mixture, or the
mixture may be applied to the clean
zinc by means of a brush.

N.B. — After vising a battery
tlie zincs must be washed and
(hied, the porous cells must
be carefully washed, and com-
pletely immersed in a large
quantity of Avater, frequently
renewed.

Fig. 81. — Large Grove's Element.

4. Grove's Cell (fig. 8r) consists of an outer glazed earthenware,
glass, or ebonite jar, containing amalgamated zinc and 10 p.c.
sulphin-ic acid. In the inner porous cell is placed platinum foil
with strong nitric acid. The platinum is the + positive pole or
anode, the zinc the - negative ])ol(' or cathode. For physiological
purposes, the small Grove's cells, about 7 cm. in diameter and 5 cm.
in height, are very convenient. When in use the battery ought to

XXV.] GALVANIC BATTERIES AND GALVANOSCOPE.

159

he placed in a draught cliaml er to prevent the nitrous fumes
from affecting the experimenti'i'.

5. Bichromate Cell (fig. 82).— This
consists of a glass bottle containing
one zinc and two carbon plates im-
mersed in the following mixture : —
Dissolve I part of potassic bichromate
in 8 parts of water, and add i part of
sulphuric acid. The zinc is attached
to a rod, which can be raised when it
is desired to stop the action of the
battery. This cell is convenient
enough when it is not necessary to
use a current of perfectly constant in-
tensity.

6. Leclanche Cell. — The positive
plate is zinc in ammonium chloride
solution (Zinc - pole). The negative
plate is carbon with manganese
dioxide in the same solution i^Car-
bon + pole).

Other forms of batteries are
used, but the foregoing are suffi-
cient for the purposes of these
exercises.

7. The Galvanoscope or De-
tector.

(a.) Charge a Daniell's cell
and attach a copper wire to
the negative pole (zinc), and

another to the positive pole (copper). On bringing the free ends
of the two wires together the circuit is made, and a current of
continuous, galvanic, or voltaic electricity
circulates outside the battery from the +
to the - pole. Prove the existence of this
current by its effect on a magnetic needle.

(b.) Use a vertical galvanoscope or de-
tector (fig. 83), in which the magnetic need e
is so loaded as to rest in a vertical position.
A needle attached to this moves over a
semicircle graduated into degrees. Con-
nect the wives from the + and - poles of the
Daniell's battery with the binding screws of
this instrument, and note that when the
circuit is made the needle is deflected from
its vertical into a more or less horizontal position, but the angle

fio. 82. — Bichromate Cell. A. The glass
vessel ; K, K. Carbon ; Z. Zinc ; I), E.
Biniling screws for the wires; B. Kod to
raise or depress the zinc in the fluid ; C.
Screw to fix B.

Fig. S3. — Detector.

l6o PRACTICAL PHYSIOLOGY. [XXVI.

of deflection is not directly proportional to the current passing in the
instrument. Break the circuit by removing one wire, and notice
that the needle travels to zero and resumes its vertical position.
The detector made by Stohrer, of Leipzig, is a convenient form.

8. Effect of Constant or Voltaic Current on the Tongue. —

Apply the free ends of the wires to the top of the tongue and note
the effect of the current ; or a key may be placed in the circuit.
The physiological effects of a moderate constant current are but
slight on the sensory nerves of the tongue, there being perhaps a
slight metallic taste.

Electrical Units are : — The unit of current is an ampere, the
unit of resistance an ohm, and the imit of pressure a volt. The
pressure or potential of a Daniell's cell is about i volt. One
ampere current is obtained by i volt pressure through i ohm
resistancp, through 20 ohms -^-^ ampere. The internal resistance
of an ordinary cell varies from i to 10 ohms.

LESSON XXVL

ELECTRICAL KEYS— RHEOCHORD.

It is convenient to make or break — i.e., close or open — a current
by means of keys, of which there are various forms.

1. Du Bois Key (fig. 84). — It consists of a plate of vulcanite,

attached to a wooden or metallic framework which can be screwed
to a table. Two oblong brass bars (II. and III.), each provided
with two binding screws, are fixed to the ebonite, while a movable
brass bar (IV.) with an ebonite handle is fixed to one of the bars,
and can be depressed so as to touch the other brass bar.

Two Ways of Using the Du Bois Key.

2. (i.) Wlien the key is chsed tJie current is made, and when it is
opened the current is broken (fig. 85). Apparatus. — Daniell's cell
and detector, three wires, and a Du Bois key screwed to a table,

(a.) As in the scheme (fig. 85) connect one wire from - pole of
the battery to one brass bar of the key. Connect the other brass
bar with one binding screw of the detector. Connect by means of
the third Avire the other binding screw of the detector with the +
pole of the cell.

{b.) On depressing the key {i.e., making the circuit) the needle
is deflected, on raising it {i.e., breaking the circuit) the needle

XXVI.]

ELECTRICAL KEYS — RHEOCHORD.

l6t

passes to zero. This method of using tlie key we may call that for
" making and breaking a current."

3. (2.) IVhen tlie keij is closed the
current is said to he '' short-circuited."
Apparatus. — Daniell's cell, detector,
four wires, and a Du Bois key.

(a.) As in sclieme (tig. 86) connect
the + pole of the battery to the outer
binding screw of one brass bar of the
key, and the - pole to the outer binding
screw of the other brass bar. Then
connect the inner binding screws of
both brass bars Avitli the detector.

{h.) Observe when the key is de-
pressed or closed, there is no deflection
of the needle, i.e., when the current is
exit off from the circuit beyond the key
or bridge ; when the key is raised, the
needle is deflected. When the key is
depressed, the current is said to be
*' short-circuited," for the key acts like
a bridge, and so a large part of the
current passes through it back to the
battery, while only an excessively feeble
current passes through the wires beyond
the key ; so feeble is it that it does not
affect a nerve. On raising the key, the whole of the current passes

Fig. 84.— Du Eois-Reymoml's Key.

Fig. 85.— Siliemc of Da l!<.i.s Key.
B. Battery ; K. Key ; N. Keive ;
M. Muscle.

Fig. 86.— Scheme of Du Bois Key
for Short-Circuiting. N. Nerve ;
-W. Muscle ; B. Battery ; /T'.Key

tlirough the detector or nerve, as the case may be. This method
of using the key is called the method of " short-circuiting."

l62

PRACTICAL PHYSIOLOGY.

[xxvi.

(c.) Test the effect of a galvanic current by applying the
electrodes to the tip of the tongue.

N.B. — In using the key to apply an induction current to excite
a nerve or muscle, always use this key by the second method, i.e.,
always place a short-circuiting key in the secondary circuit.

4. Mercurial Key. — Where st, fluid contact is required the wires
dip into mercury. Study the use of this key. It is used in the
same way as a Du Bois key.

5. Morse Key (fig. 87).— If it is desired to make or break a
current rapidly, this key is very convenient. If this key be used
to make and break the primary circuit, connect the wires to B

and C ; when the style of
the lever, I, is in contact
with c, the current does
not pass in the primary
circuit. On depressing the
handle, K, the primary
circuit is made. If, how-
ever, the wires be con-
nected to A and B, the
current passes and is
broken on depressing K.
To use this key as a short-
circuiting key, connect the wires from the battery to A and B, and
those of the electrodes to A and C. The current is short-circuited
until K is depressed, when the current passes from C to A through
the electrode wires.

6. The Contact- or Spring-Key (fig. 88) is also very useful for

Fig. 87.— Morse Key. The connections are con-
cealed below, but are Biol, A to c, C to C.

Fig. 88.— Spring-Key.

Fig. 89.— Plug-Key.

rapidly making and breaking a circuit, or for giving a single shock,
as in estimating the work done during the contraction of a muscle.
The current can only pass between the binding screws when the
metallic spring is pressed down. The left end of the spring is in
metallic contact with the upper binding screw, while the second

XXVI.J

ELECTRICAL KEYS — IIHEOCHORD.

163

binding screw is similarly connected with the little metaUic peg
at the right-hand end of the fig.

7. Phig-Key (fig. 89). — Two brass bars are fixed to a ])icce of vulcanite.
The circuit is made or broken by inserting a brass plug between the bars.
Each brass bar is ])rovided with two binding screws, to which one or two
wires may be attached, so that it can be used like a Du Bois key, either by
the first or second method.

8. The " Trigger or Turn-Over Key" is referred to in Lesson XXXV.

9. For Brodie's " Rotating Key," see Lesson XXYIIL

Means of Graduating a Galvanic Current. — Besides altering
the number, arrangement, or size of the cells themselves, we can
use a simple rheochord to divide the current itself, the battery
remaining constant, so that weak constant currents of varying
strength can thus be easily obtained.

with its ends connected to

10. The Simple Rheochord consists of a brass or German-silver
wire, about 20 ohms resistance and i metre in length, stretched
longitudinally along a board, and
binding screws and
insulated (fig. 90), On
the wire there is a
" slider " which can
be pushed along as
desired. Apparatus.
— Simple rheochord,
Daniell's cell, detector,
Du Bois key, five
wires.

(a.) Arrange the ex-
periment as in fig. 90.
When the slider S is

^<^y--^^^

Fig. 90.— Scheme of Simple Rheochord. B. Battery ;
A. Key ; W, R. Wire ; S. Slider ; D. Detector.

hard up to W, practically all the electricity passes along the wire
(W, R) back to the battery.

(6.) Pull the slider away from "W, and in doing so, the resist-
ance in the detector circuit is diminished, and some of the elec-
tricity passes along the detector circuit or the " deriving circuit "
and deflects the needle. The deflection is greater — but not pro-
portionally so — the further the slider is removed from "\V. The
deflection is nearly proportional to the distance of the slider from
W, when the resistance in the detector circuit is great compared
with that of the rheochord, which is, of course, the case when a
tissue occupies the place of the detector.

164

PRACTICAL PHYSIOLOGF.

[xxvi.

(c.) Make a table showing the extent of deflection of the needle
of the detector according to the distance of S from W.

11. The wire of the rheochord may be arranged as in fig. 91 ;
a shder, S, S, consisting of an ebonite cup filled with mercury,
can be moved along the wires. IMake connections as in fig. 91.
Observe as the mercury cup is pulled away from the binding

Fig. 91.— Rheochord with Hg-Slider, S. S. B. Battery ; K. Contact Spring-Key ;
E. Eleutrodes ; N. Nerve or Detector.

screws there is a greater deflection of the needle, but the deflection
is not in proportion to the distance of the cup. Make a table of
your results.

Distance of Hg-

Deflection of Gal-

Bridge in cm.

vanometer.

I

I

2

2-5

3

4

4

6

ID

9-5

15

II

20

12-5

30

14

The resistance in the rheochord circuit is low as compared with
that in the principal circuit. By means of the slider the resistance
in the deriving circuit can be increased or diminished, and, con-
sequently, the magnitude of the current diverted into the principal
circuit. The rheochord also affords a means of dividing a current
into two parts, according to the respective resistances in the
two circuits. A rheochord is also used to compensate any current
of injury in nerve and muscle in rheotonic experiments.

12, Simple Rheochord. — The most convenient form is that
shown in fig. 92, and is that used in the Physiological Laboratory

XXVI.]

ELECTRICAL KEYS — IlHEOCHORD.

165

of Oxford. It consists of a German-silver Avire about 20 ohms
resistance, wound round ebonite pegs fixed at equal distances at
the opposite ends of a wooden board. The board is divided into
oblongs, so that each division represents y^^ part of the whole
length of the wire, which ends in two block terminals, A, B, each
provided with two binding screws. One of the terminals of the
electrodes is attached to one terminal of the wire (A), and the other
to the movable block S, which represents a slider, and which can
be applied to any part of the Avire, at any distance from A. Owing
to the great resistance of the nerve as compared with that of the
wire, the current through the nerve or muscle is in proportion
to the length of wire between the slider S and the block.

(a.) Connect a Daniell's cell as in fig. 92 with the two block
terminals (A, B) interposing a spring-key (K). Of the electrode
wires one is connected to A, an 1 the other to the slider S,

KiG. 92.— Simple Elieocliord as used in Oxford. FiG. 93.— Thomson's Reverser.

B. Battery ; K. Spiiiig-Key ; A. B. Terminals
of Rheocfiord Wiie ; S. Slider ; i\'. Neive.

Expose the sciatic nerve of a frog, and place the electrodes
under it, or make a nerve-muscle preparation and stimulate the
nerve. Place the slider close to A, there is no response either at
make or break. Place the slider at different distances from A,
and note when contraction occurs at make.

13. Pohl's Commutator. — Sometimes it is desired to send a current
through either of two pairs of wires. This is done by means of Pohl's
commutator without the cross-bars (Lesson XXXIIL, tig. 112). At other
times it is desired to reverse the direction of a current. This is done by
Pohl's commutator with cross-bars.

t66

Practical physiology.

[xxvii.

14. Thomson's Eeverser (fig. 93) may be used to reverse the direction of a
constant current. The wires from the battery are connected to the two lower,
and those from the electrodes to the upper binding screws. The binding
screws are four in number, and placed behind the circular disc seen in the
figure. When the handle is horizontal the current is shut off from the
electrodes, while the direction of the current is reversed by raising or
lowering the handle. This instrument is used solely for reversing the
direction of a current.

LESSON XXVII.

INDUCTION MACHINE— ELECTRODES.

1. Induced or Faradic Electricity is most frequently employed
for physiological purposes. Induction shocks are of short dura-
tion, while they are physiologically very active, and they may be
employed as single shocks, or a succession of shocks may be applied.
Indeed, the fact that the application of successive induction shocks

Fig. 94— Induction Apparatus of Du Bois-Reymond. R'. Primary, R". Secondary spiral ;
B. Board on which R" moves; /. Scale; + -. Wires from battery; P', /'".Pillars;
£■. Neef's hammer ; B'. Electro-magnet ; S. Binding screw touching the steel spring
(H); S', and S". Binding screws to which are attached wires when Neef's hammer
is not required.

but slightly impairs the physiological activity of the tissues, and
that the intensity of these shocks can be accurately graduated, make
induced electricity so valuable as a stimulus in physiological
experiments.

2. Induction Apparatus of Du Bois-Reyniond. — In fig. 94 the
primary coil (R') consists of about 150 coils of thick insulated
copper wire, the wire being thick to offer slight resistance to the

XXVII.] INDUCTION MACHINE — ELECTRODES. 167

galvanic current. The secondary coil (R") consists of 6000 turns
of thin insulated copper wire arranged on a wooden bobbin ; the
whole spiral can be moved along the board (B) to which a milli-
metre scale (1) is attached, so that the distance of the secondary
from the primary spiral may be ascertained. At one end of the
apparatus is a Wagner's hammer as adapted by Neef, which
is an automatic arrangement for making and breaking the primary
circuit. When Xeef's hammer is used to obtain what is called an
interrupted cm-rent, or "repeated shocks," the wires from the
battery are connected as in the figure, but when single shocks are
required, the wires from the battery are connected Avith a key, and
this again with the two terminals of the primary spiral, S"
and S'".

Suppose M-e place the secondary coil hard up over the primary,
and consider this as zero, then an index on the side of the slot will
give the distance in millimetres of the secondary from the primary
coil, the current being strongest when the secondary coil is com-
pletely over the primary, and diminishing as the secondary is
removed from the primary.

3. New Form of Inductorium. — Fig. 96 shows an inductorium where the
secondary spiral moves vertically in a slot, and is compensated by means of a
counterpoise, so that it moves easily. It is used in the same way as the
other form.

4. Graduated Induction Apparatus. — In the ordinary apparatus the dis-
tance between the secondary and primary spirals is indicated by a millimetre
scale attached to the instrument. When the secondary spiral is moved along
equal distances, there is not a corresponding increase or decrease in the in-
duced current ; on the contrary, the strength of the induced currents under-
goes a very unequal change. Fick and Kronecker use a graduated induction
apparatus ; one side of the slot is provided with a millimetre scale, and the
other is divided into units.

5. Bowditch's Rotating Secondary Spiral. —The secondary spiral is with-
drawn from the primary to the unit mark 30 on the scale. The secondary
spiral rotates on a vertical axis, so that it can be placed at varying angles with
the primary. In proportion as it is rotated from its conaxial position the
current is diminished. The student may test this by removing the secondary
spiral from the slot and placing it at variable angles to the primary spiral.

6. Ewald's Sledge Coil. — This coil is, with the exception of the interrupting
arrangement, in every respect similar to the ordinary Du Bois-Reymond coil ;
the iron core (fig. 95, K) is arranged movable, and the secondary coil slides
over the primary and can be adjusted in any j)Osition by means of a rack and
pinion arrangement. The interrupter consists of an upright electro-magnet,
over the poles of which swings a small steel bar-magnet ; this magnet forms
the bottom end of a pendulum which swings with very little friction, aau is
counterbalanced on its upper end by a small weight.

The electro-magnet, when traversed by the current, becomes magnetised in
such a way that its poles are the same as those of the little bar-magnet above
it, thus repelling the latter, the swing of which is limited by the stop
spring B.

i68

PRACTICAL PHYSIOLOGY.

[xxViL

The magnetic circuit now being broken, the pendulum swings back until
it again touches the contact D, when it is repelled again, and so on.

According to the position which is given to the spring by means of the
milled head A, the amplitude and speed of the interrupter swings can be
varied between the limits of i and 200 per second.

Z, Z are the battery, terminals j P and S the terminals for primary and
secondary current (iig. 95),

7. Hand-Electrodes (fig. 97). — {a. ) Take a piece of double or twin wire (No.
16) enclosed in gutta-percha (that used for electric bells), about 6-7 cm. long
(2I-3 inches). Remove the gutta-percha from the ends. By means of a file
taper one pair of ends to blunt points, to the other ends solder pieces 60-90
cm. long (2-3 feet) of thin copper wire. Coil the thin wires round a glass or
wooden rod to make them into a spiral, and to their free unattached ends
solder thicker co{iper wire i inch long.

(b.) Take two pieces of flexible gutta-percha coated wire (No. 20) 60 cm.
long, and two iiieces of thick glass tubing 8 cm. long, having a bore
sufficient to admit the wire. Push a wire through each tube, and allow

Via. 95.— Ewald's Sletlgre Inductorium. S". Secondary coil moved by milled head R: K.
Core of primary coil; A. Milled head to alter position of stop D\ C. Magnet; Z, Z.
Battery terminals; P and S. Those for primary and secondary current. (It is made
by A. Hurst and Co., 66 Fenchurch Street, London, and costs £4, 10s.)

the end of the wire to project 2 cm. beyond the tube ; scrape the gutta-
percha off the free ends of both wires. Fix the wires in the glass tubes
with sealing-wax, and with a well-waxed thread bind the two tubes together.
Or use two jueces of No. 20 guttapercha coated wire, each 10 cm. in
length, fix them in glass tubes, as shown in the figure, by means of gutta-
percha cement. To the ends of the co})per wires solder thin silk-covered wires,
and to the free ends of the latter solder a short length (2 cm.) of thick un-
coated copper wire. A very handy holder is made by thrusting two fine
insulated wires (No. 36) through the bone handle of a crotchet-needle.

8. Shielded Electrodes.— For some purposes, e.g., stimulation of the vagus,
these electrodes are used, i.e., the i)latinum terminals are exposed only on one
side, the other being sunk in a piece of vulcanite (figs. 197, 226). A pair

XXVII.] INDUCTION MACHINE — ELECTRODES.

169

of shielded electrodes is easily made by fixing the ends of two fine wires —
arranged parallel to each other and about one-eighth of an inch apart — in a
thin layer of gutta-percha cement. A little of the cement is scraped off to
expose a small piece of both wires.

9. Du BoiB-Eeymond Electrodes (fig. 98).— The two wires end in triangu-
lar pieces of platinum (P) which rest on a glass plate. The whole is sup-
ported on a stand (V), and can be moved in any direction by the universal
joint (B).

Fia. 96.— Inductorium with Secoiidaiy
doil Moving in a Vertical Slut.

Fia. 07. — Hand-Elec-
trodes, such as a Stu-
dent is required to
make for himself.

10. Polarisation of Electrodes. — When a constant current is
led througli a nerve for some time it causes electrolysis where the
metalUc wires come into contact Avith the Uquids of the nerve.
The excitability of the nerve is altered by tlie secondary electro-
motive changes thus produced, so that the nerve is thereby excited,
and the muscle is thrown into contraction. Apparatus, — Elec-
trodes (fig. 97), two wires, Du Bois key, Daniell's cell, frog.

(a.) Pith a frog (Lesson XXIX 1), lay it belly downwards on
a frog-plate, and expose one sciatic nerve.

I/O

PRACTICAL PHYSIOLOGY.

[XXVII.

(b.) Screw the Du Bois key to the table, place the copper elec-
trodes under the sciatic nerve, and connect their other ends each
with the outer binding screw of the brass bars of the Du Bois key.
Close the key, and observe that no contraction of the leg muscles
occurs.

(c.) Connect a Daniell's cell with the Du Bois key. Open the^
key to allow the constant current to pass through the nerve for

Via. 98.— Du Bois ■Reymoml's Platinum Electrodes. The nerve is placed over the two
pieces of platinum, P, which rest on glass; B. Universal joint; V. Support.

three or four minutes, and observe that there is no contraction as
long as the constant current is passing. Close the key, i.e., short-
circuit the battery, and at once a contraction occurs. Remove the
battery, close and open the key. Contractions occur, but they
gradually get feebler as the polarisation ceases. The contractions
are due to polarisation of the electrodes.

(d.) If non-polarisable electrodes are used, this does not happen.

11. Non-Polarisable Electrodes. See Lesson XLI.

XXVIII.]

SHOCKS AND CURRENTS.

171

LESSON XXVITI.

SINGLE INDUCTION SHOCKS — INTERRUPTED
CURRENT -BREAK EXTRA-CURRENT — HELM-
HOLTZ'S MODIFICATION.

1. Single Induction Shocks. — Apparatus. — Danioll's cell, in-
duction macliine, wires, two Uu Bois keys (or one l)u Boi.s and
one spring or mercury key), and electrodes.

(a.) Make connections as in fig. 99. The key in the primary
circuit — preferahl}'' a mercury key — is used to make or break the
primary current. To the binding screws of the secondary coil
attach two wires, and connect them to the short-circuiting Du
Bois key, and to the latter the electrodes.

Via. 99.— Scheme for Single Induction Shocks. B. Battery; E, K'. Keys; P. Primary,
aucl S. Secondary coil of the induction nmchine ; N. Nerve ; M. Muscle.

{I I.) Effect on Tongue of Single Induction Shocks. — Open the
short-circuiting key, push the secondary coil pretty near to the
primary, and place the points of the electrodes on the tip of the
tongue, or hold them between the forefinger and tlunnb moistened
with water. Close the key in the primary circuit, i.e., make the
circuit, and instantaneously at the moment of making, a shock or
prick — the closing or make induction shock — is induced in the
secondary coil, S, and is felt on the tip of the tongue or finger.
All the time the key is closed the galvanic current is circulating in
tlie primary coil, but it is only when the primary current is made
or broken that a shock is induced in the secondary coil.

{<:.) Break the primary current by raising the key, and instan-
taneously a shock— the opening or break induction shock — is felt.

{d) The hrfCth- is- strotufer than tlie rtmhe xhork. Pu.sh the
secondary coil a long distance from the primary, and, while the
electrodes are on the tongue, make and break the primary circuit.
Gradually move the secondary near the primary coil. The break
shock is felt first, and on pushing the secondary nearer the primary

1/2 PRACTICAL PHYSIOLOGY. [XXVIIL

coil both shocks are felt, but the break is stronger than the make
shock.

Note that : —

(i.) The break shock is the stronger.

(ii.) On approximating the secondary to the primary coil, a
shock is felt at make also, i.e., when the primary
circuit is made,
(iii.) If the primary circuit be kept closed, i.e., made, no

shock is felt,
(iv.) The shocks increase in intensity the nearer the
secondary coil is to the primary.
N.B. — Make a table of the results showing the distance of the
secondary coil from the primary when testing the relative effects
of M. and B. shocks.

Single M. and B. Induction Shocks (i Daniell).

Distance of Secondary Coil Etfect on Tongue.

from Primary in cm. M. B.

19 O O

18 o Slight shock.

1 7 o Stronger shock.

9 Slight shock. Maximum shock.

8 Stronger shock. ,, ,,

7 Maximum shock. ,, ,,

(c.) Remove the secondary spiral from its slot, and place it in line with
and about 15 cm. from the primary. Rotate the secondary coil so as to jilace
it at variable angles with the primary. Make and break the primary circuit,
and test how the strength of the induced current varies with the extent of
rotation of the secondary spiral.

2. Interrupted Current, i.e., Repeated Shocks, by using Neef s
Hammer^ — (Alternating Currents) — Faradisation.

(ii.) Connect the battery Avires (fig. 100) to P' ( + ) and P"( - ).
Introduce a Du Bois key as for the make and break arrangement.
The automatic vibrating spring, or Keef's hammer, is now included
in the primary circuit. Set the spring vibrating. Close tlie
key in the primary circuit. The spring, H, is attracted by the
temporary magnet, B', thus breaking the contact between the
spring, H, and the screw, S', and causing a break shock in
the secondary coil. B' is instantly demagnetised, the spring
recoils and makes connection with S', and causes a make shock.
Thus a series of make and break induction shocks following each
other with great rapidity is obtained, but the make and break
shocks are in alternately opposite directions.

XXVIII.]

SHOCKS AND CURRENTS.

173

(b.) Effect on Tongiie. — While Neef's hammer is vibrating,
apply the electrodes to the tongue as before, noting the effect pro-
duced and how it varies on altering the distance between the
secondary and ])rimary coils.

Fig. 100. Induction Coil arninj^ed for interrupted or repeated shocks, with
Neefs Hammer in tlie Primary Circuit.

(c. ) Note also how the strength of the induced shocks varies with the
angular deviation of the secondary spiral, the distance between the two
spirals being kept constant (p. 172).

3. The Break Extra-Current of Faraday. — When a galvanic
current traversing the primary coil of an induction machine is
made or broken, each turn of the wire exerts an inductive influence
on the others. When the current is nvvle, the direction of the
extra-current is arinijid that of the battery current, but at hreali it
is in the same direction as the
battery current. Apparatus. —
Daniell's cell, two Du Bois keys,
five wires, primary coil of in-
duction coil, electrodes (or nerve-
muscle preparation).

(rt.) Arrange the apparatus
according to the scheme (fig.
loi). Notice that both keys
and the primary coil of the

induction maclline are in the FiOioi-—Schenieof the Break Extm Current
„ •„ • 4. ii 1 1 • li- liatterv; A', and A". Keys; P. Primar>

primary circuit, the keys being coil ; N. Nerve ; M. Muscle.

so arranged that either the

primary coil, P, or the electrodes attached to key K', can be

short-circuited.

174

PRACTICAL PHYSIOLOGY.

[xxvni.

(h.) Test (a) either by electrodes applied to the tongue, or {/3)
by means of a nerve-muscle preparation (/3 to be done after the
student has learned how to make a nerve-muscle preparation).

{(•.) Close the key K, thus short-circuiting the coil. Open and
close key K'. There is very little effect.

(d.) Open K, the current passes continuously through the
primary coil. Open key K' ; a marked sensation is felt, due to
the break extra-current.

4. Helmholtz's Modification. — The break shock is stronger
than the make, and to equalise them Helmholtz devised the
following modification : —

(a.) Connect the battery wires as before to the two pillars (fig.

loo), P

and P", or to a and e (fig. 102). In fig. 102 connect a
wire — " Helmholtz's side wire "
— from a to /', thus bridging or
" short - circuiting " the inter-
ru]iter. Elevate the screw (/)
out of reach of the spring (c),
1)ut raise the screw (d) until it
touches the spring at every
vibration. By this means the
make and break shocks are nearly
wiualised. Test this on the
tongue. Both shocks, however,
are weaker, so that it is necessary
to use a stronger battery. The
primary circuit is never entirely
broken, it is merely weakened.

It is ahvays advantageous,
Avhen using faradic shocks for
physiological purposes, to use
make and break shocks of
nearly equal intensity, i.e., use
Helmholtz's side wire. "Why?
Because any " polarisation " produced by the one current is
neiitralised by the other. This is not the case with the ordinary
arrangement, where the break shock is stronger than the make,
wliereby there is a progressive summation of the polarisation
effects of the break shocks.

1. 102. — Helmholtz's Modification of
Neet's Hammer. As long as c is not in
contact with d, g h remains magnetic ;
thus c is attracted to d, and a secondary
circuit, a, b, c, d, e, is formed ; c then
springs back again, and thus the process
goes on. A new wire is introduced to
connect a with/. K. Battery.

5, To Approximately Equalise Single Make and Break
Induction Shocks.

A.s we have seen, the extra-current is the cause of the greater
intensity of the break shock. If, however, the intensity of the

XXVIII.]

SHOCKS AND CURRENTS.

175

extra-current be the same at make and break, tins inequality will
disapjiear.

(a.) Connect the terminals of a Daniell's cell with the top
binding screws of an induction coil, as in fig. 103, and to the

Fio. 103. — Airangement to approximately equalise M. and B. shocks
5. Secoudaiy coil ; K. Key in deriving circuit, D. D.

P. Primary,

same induction coil terminals connect two other wires with a
make and break key (K) in their circuit (" deri\dng circuit," D, D).
Thus the primary current is never broken.

(b.) Arrange the secondary coil with short-circuiting key and
electrodes.

(r.) On closing the key in the deriving circuit the current in
the primary coil is diminished, and on opening it the primary
current is increased. Induced currents of opposite directions
are thereby produced, which, though weaker than the make
induction shock, are approximately equal to each other.

6. To Eliminate either M. or B. Shocks. — For this purjwse the " Rotating

Key " devised by Gregor Biodie is most useful. It consists of a horizontal
axis supported on two ebonite uprights fixed to an ebonite base (fig. 104).

Fig. 104. — Brodie's " Kotating Key " to eliminate the if. or E. shock.

This axis consists of two metal rods, A B and C D, united together by an
insulating piece of ebonite, K. A B passes through a cup, E, cut in the upright
and filled with mercury. The other rod, C D, is similarly connected to the

176 PRACTICAL PHYSIOLOGY. [XXIX.

second upright. Two stout wires, S, T, lead from the two mercury cups, E, F,
to two binding screws, 1 and 4 resjiectively. Attached to the two rods are
two metal arms, ]\1 and N, which can be rotated round the rods and clamped
in any position. These dip into two mercury troughs, P and Q, which are
respectively attaclied by stout wire to two binding screws, 2 and 3.

The action for wliich the key was devised is as follows : —

The primary ciicuit is connected with the two screws 3 and 4 ; the
secondary and a pair of electrodes with the screws 1 and 2. Then, as the
axis, A D, is rotated, the arm, M, first dips into the trough, P, and the
secondary circuit is thereby short-circuited, and remains so during the whole
time the arm, M, is in the mercury. While this is still in the mercury the
second arm, N, enters the mercury, Q, and the primary circuit is thus closed,
but, as the secondary is short-circuited, the make induced current does not
reach the electrodes. On rotating a little further, the arm, M, leaves the
mercury, and shortly after the arm, N, leaves the mercury, Q, and the current
is broken. The break induced current can now pass through the electrodes
since the secondary circuit is not now short-circuited.

By reversing the rotation only make shocks can pass through the electrodes,
the break shocks being short circuited.

The key may also be used in other ways. By placing the two arms, M and
N, parallel to one another, the key may be used to close two circuits simul-
taneously, eg:, a primary current, and a current working a signal.

Further, by altering the angular distance between M and N, and having the
axis driven at a constant rate, the key may be used for sending in two succes-
sive stimuli at different intervals of time.

LESSON XXIX.

PITHING— CILIARY MOTION— NERVE-MUSCLE
PREPARATION— NORMAL SALINE.

1. Pith a Frog. —Wrap tlie body, fore and hind legs, in a towel,
leaving the head projecting. Grasp the towel enclosing the frog
with the little, ring, and middle fingers and thumb of the left hand,
leaving the index-finger free. "With the index-finger bend down
the frog's head over the radial surface of the second finger until
the skin over the back of the neck is put on the stretch. "With
the nail of the right index-finger feel for a depression where the
occiput joins the atlas, marking the position of the occipito-
atlantoid membrane. With a sharp, narrow knife held in the
right hand, divide the skin, membrane, aijd the medulla oblongata.
Withdraw the knife, thrust a " seeker " into the brain cavity-
through the opening just made, and destroy the brain. To prevent
oozing of blood, a piece of a wooden match may be thrust into the
brain cavity. If it is desired, destroy also the spinal cord with
the seeker or a wire. The knife used must not have too broad a

XXIX.] PITHING CILIARY MOTION, ETC. 177

blade, else two large blood-vessels will be injured. The operation
should be performed without losing any blood.

2. Ciliary Motion.

(a.) Destroy the brain and spinal cord of a frog. Place the
frog on its back on a frog-plate covered with cork well- waxed or
coated with paraffin. Divide the lower jaw longitudinally, and
carry the incision backwards through the pharynx and oesophagus.
Pin back the flaps. Moisten tlie mucous membrane, if necessary,
with normal saline.

(b.) Make a small cork flag, and rest it on the mucous mem-
brane covering the hard palate between the eyes. It will be
rapidly carried backwards by ciliary motion towards the stomach.
Eepeat the experiment, and determine the time the flag takes to
travel a given distance.

(c.) Apply heat to the preparation, and observe that the cork
travels much faster.

{(l.) Grains of charcoal or Berlin blue are carried backwards in a similar
manner.

(c. ) With a hot wire cauterise superficially a small area of the mucous
membrane in a preparation bestrewn with grains of charcoal. The ciliary
movement stops not only at the cauterised area, but also in a triangular
area whose apex is at the burned point, and whose base is directed towards
the oesophagus. It would seem, therefore, that the movements of the cilia
in individual cells are not independent of the movements in neighbouring
cells.

3. Anatomy of the Nerve-Muscle Preparation.— Before mak-
ing this preparation, the student must familiarise himself with
the anatomy of the hind limb of the frog. On a dead frog study
the arrangement of the muscles, as shown in fig. 105, The skin of
the frog is removed, the frog placed on its belly, and the muscles
viewed from behind. On the outside of the thigh, the tricepx
feworis (tr), composed of the rectus anferiar (ra), the vastus
ezferriHS (ve), and the va-^tus intermis, not seen from behind. On
the median side, the semi-membranosus (*7?i), and between the two
the small narrow biceps (b). The biceps is readily observed, at
the lateral margin of the large semi-membranosus, by its shining
tendon in the middle of the lower half of the thigh. Notice, also,
the coccygeo-il iacus (ci), the tjluteus (gl), the pgri/ormis (p), and
the 7-ectus internns minor (ri). In the leg, the rjas/rornfmius (g),
"with its tendo Achillis, the tibialis anticus (ta), and the peroneus
(pe).

4. Make a Dissection.

(a.) Remove the skin from the leg of a dead frog ; with a blunt
needle, called a " seeker " or a " finder," or a glass rod drawn out to

178

PRACTICAL PHYSIOLOGY.

[xxix.

a point, gently tear through tlie fascia covering the thigh muscles,
and with the blunt point of the finder separate the semi-mem-
branosus from the biceps, and in the interval between them observe
the sciatic nerve and the fe^noral vessels. Carefully isolate both,
beginning at the knee, where the nerve divides into two branches
— the tibial and peroneal — and work upwards (fig. io6).

Fig. 105.— The Muscles of the Left Leg
of a Frog from behind, ci. Ooccy-
geo-iliacus ; gl. Gluteus ; p. Pyri-
forniis; ra. Rectus anterior; ve.
Vastus externus; tr. Triceps; ri.
Kect. int. minor ; sm. Semimem-
branosus; b. Biceps; g. Gastro-
cnemius ; ta. Tibialis auticus ; pe.
Peroneus.

FiS. 106. — Disti iliution of the Sciatic
Nerve (L) of tlie Frog (see also fig.
105). St. Seinitendinosus; ad'".
Adductor magnus ; (II.) its tibial,
and (III.) peroneal divisions.

The tibial branch passes over the knee-joint towards the middle line, and
enters the under surface of the gastrocnemius ; the j)eroneal branch j)asses
between the lateral tendinous origin of the gastrocnemius and the tendon of the
biceps, and then under the latter,

(h.) Follow the nerve right upwards to its connection with the
vertebral column, and observe that it is necessary to divide the

XXX.]

NERVE-MUSCLE PREPARATION, ETC. 1^9

pyriformis (^9), and also the ilio-coccygeal muscle, when the three
spinal nerves — the 7th, 8th, and 9th — which form the sciatic nerve,
come into view. It can be seen from the abdominal side after
opening the belly and removing the viscera, including the kidneys.
On its way from the sacral plexus to the thigh, it gives off cutan-
eous and muscular branches for the pelvis and thigh.

5. Double Semi-Membranosiis and Gracilis [Fick's Method). — I am indebted
to Prof. Fick and Dr Sclienk of Wiirzburg, for showing me the method of pre-
paring this— one of the most convenient of preparations.

{a.) After jiithing a frog, and removing its skin to expose the muscles of the
hind limbs, remove the few fibres of the rectus internus minor which are torn
across when tlie skin is torn otf. Divide the fascia at the outer margins of the
semi-membranosus and gracilis, until the insertion of these two muscles into
the knee is reached, then, with strong scissors, divide the leg bone just un^ler
the knee-joint, so that the osseous insertion of both muscles is retained.
Divide the femur just above the knee-joint, and separate all the muscles in-
serted into it, save the two muscles one is isolating. Se})arate the two muscles
from the other muscles of the thigh up to the symphysis. Leave the two
muscles in connection with the symphysis, divide the other muscles, disar-
ticulate the femur at the acetabulum. In preparing the muscles in this way
the semi-tendinosus, which lies between the two on the side towards the bone,
is usually left. It is easy to separate it by dividing its insertion into the
femur, and then its two heads at the pelvis.

{b. ) Make a similar dissection on the opposite side. Bore a hole with an awl
through both acetabula. Through this a hook can be placed.

Thus we have two muscles with nearly straight fibres which can be placed
" side by side," thus giving a short muscle with great sectional area, or they
can be placed "one behind the other," a piece of bone, the symjihysis inter-
vening, thus giving a long muscle with half the sectional area. This prepara-
tion is extensively used by Prof. Fick, and has many advantages.

6. Indifferent Fluids — Normal Saline. — Dissolve 6 grams of dried sodic
chloride in 1000 cc. of water. This is the best fluid to use to moisten tissues
when a large quantity is required. For nerve the aqueous humor of the frog's
eye is the best. It can readily be obtained by perforating the cornea with a
fine glass pipette.

LESSON XXX.

NERVE - MUSCLE PREPARATION — STIMULATION
OF NERVE— MECHANICAL, CHEMICAL, AND
THERMAL STIMULL

1. Nerve-Muscle Preparation. — Apparatus. — Frog, seeker,
narrow-bladed scalpel, a small and a large pair of scissors, forceps,
towel, and a porcelain plate.

(A.) {a.) Pith a frog, destroyhig tlie brain and spinal cord, and
place the frog on its belly on a frog-plate. With scissors make an

i8o

PRACTICAL PHYSIOLOGY.

[xxx.

incision through the skin along the back of one thigh — say the left
— from the knee to the lower end of the coccyx, and prolong the
incision along the back a little to the left of the nrostyle. Reflect
the skin, and expose the muscles shown in fig. 105.

(b.) Gently separate the semi-membranosus and biceps with the
" seeker," and bring into view the sciatic nerve and femoral vessels.
Some use a glass rod drawn to a tliin prolonged point, instead of a
"seeker." tStill working with the seeker and beginning near the
knee, clear the sciatic nerve, but do not scratch or stretch the nerve,
or touch it with forceps. Divide the pyriformis and ilio-coccygeus,
and trace the nerve up to the vertebral column.

(r.) Divide the spinal column above the seventh lumbar vertebra ;
seize the tip of the urostyle with forceps, raise it, and with the strong
scissors cut it clear from all its connections as far as the last lumbar
vertebra, and then divide the urostyle itself. Divide the left ihac
bone above and below, and remove it with the muscles attached to
it. The lumbar plexus now comes into view. Bisect lengtliways
the three lower vertebrse, and use the quadrilateral piece of bone
by which to manipulate the nerve. With forceps lift the fragment
of bone, and with it the sciatic nerve ; trace the latter downwards
to the knee, dividing any branches with
fine scissors. Keep the parts moist with
normal saline.

(d.) Divide the skin over the gastroc-
nemius, and expose this muscle. Divide
the tendo A chillis below its fibro-cartilage,
lift the tendon with forceps and detach the
gastrocnemius from its connections as far up
as the lower end of the femur. Cut across
the knee-joint, and remove the tibia and
fibula with their attached muscles. Taking
^. .™ care to preserve the sciatic nerve from

ly IJ injury, clear the muscles away from the

li\ ^I lower end of the femur, and then divide the

Fig. 107. — Nerve - Muscle femur itself about its middle. This prepara-
Prepaiation. s. Sciatic tion (fig. lo?) consists of the gastrocnemius,

nerve — the fragment of t li 11 1 ,i r ^i • i.-

the spinal column is and tlie wholc length 01 the sciatic nerve,
i.otshrMvn;F Femur; to which is attached a fragment of bone,

and /. Tendo Aclullis. , • 1 , 1 , • i -1^1

by wlucn the preparation can be manipulated
without injuring the nerve. N.B. — The nerve must not be touched
with instruments, neither stretched nor scratched, nor allowed to
come into contact with the skin, and it must be kept moist with
normal saline.

(B) (a.) Another metliod is sometimes adojjted. Destroy a frog's brain
and spinal cord. With the left hand seize the hind limbs and hold the frog

XXX.]

NERVE-MUSCLE PREPARATION, ETC.

i8r

with its belly downwards. With one blade of a sharp-pointed pair of scissors
transfix the body immediately behind the shoulder-blades, and divide the
spinal column. The head now hangs down, and by its weight it pulls the
ventral from the dorsal parts.

{b.) With the scissors divide the wall of the abdomen on both sides parallel
to the vertebral column, and remove the abdominal viscera. With the left
hand seize the upper end of the divided spinal column, and with the right the
skin covering it, and pull. The lower end of the trunk and the lower limbs
are denuded of skin.

(c.) Take the thigh muscles between the thumb and forefinger of the left
hand, and with the point of one blade of a pair of scissors tear through the
fascia between the biceps and semi-membranosus to expose the sciatic nerve,
and then proceed as directed in 1.

2. Stimuli may be classified as follows : —

(i.) Mechanical, e.g., cutting or pinching a nerve or muscle.
(2.) Chemical, e.g., by dipping the end of a nerve in a saturated
solution of comniou salt or glycerin.

(3.) Thenual, e.g., applying the end of a heated wire to the
nerve.

[ (a.) Continuous current.
(4.) Electrical — < [b.) Single induction shocks.

\ (c. ) InteiTupted current or repeated shocks.

3. Stimulation of Muscle and Nerve. — It is convenient to
modify somewhat the physiological limb, in order to render the
muscular contraction more visible. Apparatus. — Seeker, scalpel,
scissors, forceps, straw flag, pins, muscle-forceps, camel's-hair brush,
saturated solution of common salt in a glass tliimble, ammonia,
copper wire, spirit lamp or gas-flame.

4. Mechanical Stimulation.

{■!.) Destroy tlie brain and spinal cord of a frog (Lesson XXX. 1).
Prepare a nerve-muscle preparation, isolat-
ing the sciatic nerve, but modify tlie sub-
sequent details as follows : —

\h.) After the nerve is cleared as far
as the spine, clear the muscles away from
the femur, and divide the latter about
its middle. Divide the sciatic nerve as
high up as possible. Pin a straw flag to
the toes by means of two pins. Fix the
femur in a clamp 01 pair of muscle-forceps,
supported on a stand (tig. 108), taking care
that the gastrocnemius is upwards. The
nerve hangs down, and must be manipu-
lated with a camels-hair brush dipped in normal saline, or by
means of a hooked glass rod.

Fig. 108.— Straw Hag attached
to a Frog's Leg tlxed in a
Clamp. A'. Nerve; 7-'. Flag.

1 82 PRACTICAL PHYSIOLOGY. [XXX,

(c.) Pinch the free end of the nerve sharply with forceps; the
muscles contract and the straw flag is suddenly raised. Cut off
the dead part of the nerve, contraction also occurs.

(d.) Prick the muscle with a needle; it contracts.

For the purposes of the student it is sufficient to expose o le
sciatic nerve in situ, and observe the movements of the foot an 1
leg.

Mechanical stimulation is rarely emjjloyed, as tlie part stimulated is apt to
be injured by the stimuli. Heiilenhain in 1856 devised what he called a
Tetanomotor for this purpose. It consisted of a Wagner or Neef s hammer,
with one end prolonged and carrying a small ivory hammer, which beat the
nerve placed under it. Recently v. Uexkiill has devised apparatus for this
purpose {Zeits. f. Biol., Bd. xxxi.).

(c.) Mechanical Stimulation by removal of pressure. — Place the nerve of a
nerve-muscle preparation on a moist glass plate, press the nerve slowly and
steadily with a curved i mm. thick glass hook. If pressure be applied
steadily and uniformly the nerve is not excited, but on suddenly removing
the pressure the muscle contracts {v. Uexkiill).

5. Thermal Stimulation.

(a.) To the same preparation apply, either to muscle or nerve,
a wire or needle heated to a dull heat ; a contraction results in
either case. Cut off the dead part of the nerve.

6. Chemical Stimulation.

(a.) Place saturated solution of common salt in a glass thimble,
or on a glass shde, and allow the free end of the nerve to dip
into it. Owing to the high specific gravity of the saline solution,
the nerve floats on the surface, but sufficient salt diffuses into
the nerve to stimulate it. After a few moments, the joints of
the toes twitch, and by-and-by the whole limb is thrown into
irregular, flickering spasms, which terminate in a more or less
continuous contraction, constituting tetanus. Cut off the part
of the nerve affected by the salt ; the spasms cease. Some apply
finely powdered salt to the nerve, others glycerin.

{b.) Using a similar preparation, cover the leg with the skin of
the frog, or wrap it in blotting-paper saturated with normal saline.
Expose the fresh-cut end of the jierve to the vapour of strong
ammonia. The ammonia must not act directly on muscle, hence
the glass vessel must be placed above the nerve, and the nerve
raised to the ammonia. There is no contraction of the muscle, but
the ammonia kills the nerve.

Instead of doing this, the whole leg may be laid on a card, covered with
blotting-paper moistened with normal saline, with a hole in it just sufficient
to allow the sciatic nerve to jiass through it. The card is placed over a
test-tube containing a drop of ammonia ; the nerve hanging in the vapour
of the latter is speedily killed, but there is no contraction of the luuscle.
Apply ammonia to the muscle ; it contracts.

XXXI.]

ELECTRICAL STIMULATION.

183

Note that although ammonia aj)i)lied directly to a motor nerve does not
cause contraction of the corresponding muscle, yet when it is applied to
the central end of the divided vagus of a rabbit it causes marked rellex
movements of the respiratory muscles.

7. Drying. — If the nerve be allowed to hang freely in the air
for some time, it gradually dies, and the muscles twitch irregularly,
as when a nerve is stimulated chemically. Moisten the nerve
with normal saline and the twitching riiaij cease. It may be
that glycerin acts as a stimulus through absorbing water.

LESSON XXXI.

SINGLE AND INTERRUPTED INDUCTION SHOCKS

—TETANUS -CONSTANT CURRENT.

1. Electrical Stimulation — Single Induction Shocks. — Appa-
ratus.— Daniell's cell, induction machine, two Du Bois keys (or
one spring key or mercury key and one Du Bois key), five wires,
electrodes.

(a.) Arrange a cell and induction machine for single induction
shocks as in fig. 109. A spring contact-key or Ilg-key is more

Fig. 109.— Scheme for Single IiKhietion Shocks. B. Battery ; K, K'. Keys ; P. Primary,
and S. Secondary coil of the induction machine ; N. Nerve ; M. Muscle.

convenient in the primary circuit. Electrodes are fixed to the
short-circuiting key (K') in the secondary circuit, and over them
the nerve is to be placed.

(/'.) Expose the sciatic nerve in a pithed frog, place it on electrodes
— preferably a pair fixed in ebonite, and so shielded that only
one surface of their platinum terminals is exposed under it. Or
use the simple shielded electrodes described in Lesyon XXVIT. 6.
Pull the secondary coil (S) far away from the primary (P), raise
the short-circuiting key (K'), make and break the primary circuit

1 84

PRACTICAL PHYSIOLOGY.

[xxxi.

by means of the key (K). At first there may be no contraction,
but on approximathig the secondary to the primary coil a single
muscular contraction will be obtained, first with the break shock,
and on approaching the secondary nearer to the primary coil, also
with the make. The one is called a make and the other a break
contraction. Enter in a note-book the results obtained. N.B. —In
all cases the student should keep an account of the experiment,
and especially of all numerical data connected therewith, e.g. : —

Single make and break shocks — Du Buis indudorium with
I Daniell.

Distance of Primary from

Secondary Circuit

in cm.

Response at
Make (M).

Response at Break
(B).

45

O

O

44

o

Min. twitch.

43

o

Slight ,,

42

o

Stronger ,,

41

o

,, ,,

20

o

Max. ,,

19

Slight twitch.

,, ,,

i8

Max. ,,

>> >»

Compare Ordinary with Helmholtz Arrangement, and tabulate
the results as follows, to show the distance of the secondary coil
at which mechanical response first occurs.

Ordinary Du Bois-
Reyuioud Coil.

With Helmholtz's
Modification.

Nerve make, .
, , break,

The same may be done by applying the electrodes directly to the
gastrocnemius muscle, i.e., direct stimulation, that through the
nerve beinji indirect stimulation.

Ordinary Du Bois-
Reymond Coil.

With Helmholtz's
Modification.

Muscle make,
,, break.

XXXI.j ELECTRICAL STIMULATION. 1 8$

2. Interrupted Current or Repeated Shocks.

(a.) Arrange the induction machine so as to cause Neef s hammer
to vibrate as directed in Lesson XXVIII. 2. On applying the
electrodes to the sciatic nerve or gastrocnemius muscle, at once
the muscle is thrown into a state of rigid spasm or continuous
contraction, called tetanus, this condition lasting as long as the
nerve or muscle is stimulated, or until exhaustion occurs.

3. Constant Current. —Appai'atus. — DanielFs cells, Du Bois
key (or, preferably, a simple make and break key), four wires,
electrodes, forceps, and nerve-muscle preparation, or simply expose
the sciatic nerve in situ.

(a.) Use two Daniell's cells. If two or more Daniell's cells be
used, always conuect them in series, i.e., the -f pole of one cell
with the - pole of the next. Connect two wires, as in fig. no,
to the free + and - poles of the battery
B, and introduce a Du Bois key (K') to
short-circuit the battery circuit. Fix two
shielded electrodes in the other binding-
screws of the Du Bois key, and having
prepared a nerve-muscle preparation, lay
the divided sciatic nerve (N) across them,
as shown in fig. no. A simple key to
make or break the current is preferable
to the short-circuiting key, as the latter
allows polarisation currents to pass when it

is closed. Pj^ i,o.— scheme of Con-

(/>.) INIake and break the current, and a staut Current. £. Battery;

. 1 1 i i- X -i 1 • A". Short-circuiting key;

single muscular contraction or twitch is A'. I^erve; J/. Muscle.

obtained, either at making or breaking, or

both at making and breaking. Xotice that if the key be raised

to allow the current to flow continuously through the nerve, no

contraction occiu-s, provided there be no variation in the intensity

of the current. The electrodes may also be applied to the muscle

directly.

(c.) Rapidly make and break the current by opening and
closing the key ; a more or less perfect tetanus is produced.

('/.) If it be desired to test the effect of a constant current on
muscle alone, then the terminations of the motor nerves in the
muscle must have been paralysed previously by curare, so that
in this case the electrodes must be applied directly to the
muscle.

4. Muscle on Mercury. — Lay the muscle of a nerve-muscle
preparation on the surface of mercury. Stimulate the nerve, the

1 86 PRACTICAL PHYSIOLOGY. [xXXt

mxiscle contracts, but does not elongate : it shows little tendency
to elongate uidess it be weiglited.

5. Dead Muscle and Nerve. — Immerse a nerve-muscle preparation for a
few minutes in water at 40' C. Both are killed, and none of the above
stimuli cause contraction.

6. The Sartorius. — One gets a clear idea of the shortening and thickening
which occur whtn a muscle contracts by using the sartorius, as its fibres are
arranged in a parallel manner.

(n.) Pith a frog, lay it on its liack, and dissect off the long narrow sartorius
from the inner side of the thigh. The thin narrow sartorius (fig. iii)
stretching from the ilium to the tibia is best seen if it be moistened with
blood, which differentiates its edges. To isolate
the sartorius the best way is to cut the other
parts away from it. Raise its tibial tendon, and
round it tie a fine silk tiiread. Gradually raise
the muscle by means of the thread, and with fine
scissors cut it free from its fascial connections
right u[) to the ilium. Cut it out with the ilium
attached. Its nerve enters it on its under surface
about the middle of the muscle. Wlien it is
divided the muscle contracts. Stretch it on a
slip of glass or hang it up by its ilium bony
attachment in a claiu]).

(//.) Stimulate the muscle first at its ends and
afterwards at its centre or equator, as in Lesson
XXXI 1, 2, with (i.), a single induction shock,
and (ii.), afterwards with an interrupted current.
Oliserve the shortening and thickening, which
are much greater in (ii. ) than (i.). The muscle
may be extended again, and stimulated as
frequently as desired, if it be kept moist.

Fig. III.— Muscles of the Left 7. Unipolar stimulation. — Apparatus.
^IrrouJ'l^^v^:::^ -Danieirs cell, induction machine, Du
«. Sartorius ; «rf'. Adductor Bois keys, (muscle-chamber), wires, elec-

longus; d/. Vastus internus. j. 1 '

(See figs. 105 and 106.) trocles.

A. (a.) Expose the sciatic nerve of a
frog, and place the frog on a dry cork plate, or glass, or block of
j)aratfin. Arrange an induction apparatus for faradisation with the
electrodes short-circuited, and placed under the sciatic nerve clear
of all adjouiing muscles. Open the short-circuit key and find a
strength of cui'rent (secondary coil at 25-30 cm.) which on
faradisation gives feeble tetanus.

(b.) Disconnect one of the electrode wires from the preparation,
so that only one terminal is in connection with the nerve. There
is no contraction when the secondary key is open. Insulate tlie
preparation by placing it on a block of paraffin or on a dry
beaker,

(r.) Try to find the distance of the secondary coil (8-10 cm.)

XXXII.] STIMULATION OF MUSCLE. 1 8/

at which no response is obtained with unipolar stimulation, but a
response is obtained when the preparation is touched ^\■ith finger.
"Why is there a response ? Because l)y touching the preparation
one suddenly diminishes the resistance to the passage of the induc-
tion currents to earth.

Or B. (a.) Set up a cell and induction coil with electrodes for
single shocks. Disconnect one of the electrodes of the secondary
coil, the other one being under the sciatic nerve or the nerve of a
nerve-muscle preparation which is insulated on a glass plate. If
the frog is on a fiog-plate put the frog-plate on a dry beaker to
insulate it. Xo contraction occurs at make or break,

(/;.) Connect the disconnected electrode to a gas-pipe and so to
the earth. Contraction takes place at make or break. It is in order
to avoid unipolar stimulation that the Du Bois key is used to
short-circuit the secondary circuit.

Or C. (a.) Connect the Daniell to the primary coil of the induction machine
either for single shocks or tetanus, introducing a Du Bois key in the circuit.
Connect one wire with the secondary coil, and attach it to one of the bind-
ing screws on the platform of the muscle-chamber, to which the nerve electrodes
are attached. See that the battery and induction machine are perfectly insul-
ated by supporting them on blocks of paraffin.

(b.) Prejiare a nerve-muscle preparation, and arrange it in the muscle-
chamber in the usual way, laying the nerve over the electrodes. One of the
electrodes will therefore be connected with the secondary circuit.

(f.) Make and break the primary circuit ; there is no contraction.

(f:^. ) Destroy the insulation of the preparation by touching the muscle, or
what does better, allow the brass su})port of the muscle to touch a piece of
moist blotting-paper on the inner surface of the glass shade of the chamber.
Every time the brass binding of the shade is touched, or the brass support
itself, the mu.scle contracts. Touch the secondary coil and contraction
results.

LESSON XXXII.

RHB DNOME— TELEPHONE EXPERIMENT— DIRECT
AND INDIRECT STIMULATION OF MUSCLE-
RUPTURING STRAIN OF TENDON— MUSCLE
SOUND— DYNAMOMETERS.

1. Fleischl's Rheonome and Law of Excitation. — This instru-
ment (fig. 112) is useful for showing Du Bois-Reymond's law,
that it is not the absolute intensity of a galvanic current flowing
through a nerve which excites it, but the rapidity of the variations
in the intensity of the current wliich excite a motor nerve. It

1 88 PRACTICAL PHYSIOLOGY. [XXXII.

consists of a square ebonite base, with a grooved circular channel in
it, and two binding screws, with zinc attached, and bent over so as
to dip into the groove, which is filled with a saturated solution of
zinc sulphate. A vertical arm, with binding screws attached to two
bent strips of zinc, moves on a vertical
support. It is a kind of revolving rheo-
chord.

{a ) Connect two or three Daniell's cells
(copper to zinc) with the binding screws
A and B, introducing a Du Bois key in
one wire. Attach the electrodes, intro-
ducing a Du Bois key to short-circuit them,
to the binding screws, C and D. Fill the
^^^' Kheom)'ra^°''^^ groovB witii a saturated solution of zinc

sulpliate.
(b.) Arrange the nerve of a nerve-muscle preparation over the
electrodes, or simply expose the sciatic nerve of a frog in situ. Pass
a constant current through the nerve, observing the usual effects,
viz., contraction at make or break, or both, but none when the
current is passing. Tlien suddenly rotate the handle with its two
zinc arms ; this is equivalent to a sudden variation of the intensity
of the current ; the current, of course, continuing to pass all the
time. The muscle suddenly contracts.

When the two ends of the zinc arc stand as in the fig., i.e., o])posite C and
D, then, on closing the current, most of the current goes through the zinc arc
to the preparation, and only a small part through the zinc sulphate solution
from C to D. Thus the muscle contracts according to the direction and
intensity of tlie current, either on closing or opening the key, or at both.
Turn the handle so that the zinc arc is vertical to a line joining C and D.
There is no current, so that the prejiaration does not resjiond either on closing
or opening.

If, while the zinc arc is in this position, the circuit be closed, and the zinc arc
suddenly rotated into the })Osition of the line C, D, the muscle contracts,
provided in the first exjieriment a closing, i.e., make, contraction was obtained.
If it be rotated slowly then there is no response. Thus one can allow the
current to glide or slide into the nerve {" ei,nschle/chc7i") without causing
excitation,

2. Direct and Indirect Stimulation of Muscle. — When the
stimulus is applied directly to tlie muscle itself, we have direct
stimulation ; but when it is applied to the nerve, and the muscle
contracts, this is indirect stimulation of the muscle.

(i.) Induced Cnri-ent. — (a.) Arrange a nerve-muscle preparation,
and an induction machine for single or repeated shocks (Lesson
XXXI. 1).

(6.) Test first the strength of current- as measured by the
distance between the secondary and primary coils — which causes

XXXII.] STIMULATION OF MUSCLE. 1S9

the muscle to contract when the stimuhis is applied to the nerve,
i.e., for indirect stimulation.

(/;.) Then Avith the secondary still at the same distance from
the primary, try if a contraction is obtained on stimulating the
muscle dii'ectly. It will not contract ; but make the current
stronger, and it will do so. The excitability of muscle to direct
stimulation is best done after the nerve-terminations have been
paralysed by curare (Lesson XXXIII.).

(ii.) Constant Current. — Connect the electrodes Avith two Daniell's
cells, placing a Hg-key in the circuit. Place the electrodes under
the nerve. Contraction occurs at make only, and at break only
if the preparation is very excitable, but there is no contraction
when the current is passing through the nerve.

ADDITIONAL EXERCISES.

3. Muscle Sound.

(n.) Insert the tips of the index fingers into the auditory meatuses, forcibly
contracting the biceps muscles. A low rumbling sound is heard.

{b. ) When all is still at night, firmly close the jaws, and, especially if the
ears be stopped, the sound is heard.

4. Telephone Experiment.

(a.) Arrange a nerve muscle jjreparation with its nerve over a pair of
electrodes. Connect the latter with a short-circuiting Du Bois key. To the
key attach the two wires from a telephone.

(6.) Open the short-circuiting key ; shout into the telephone, and observe
that on doing so the muscle contracts vigorously.

5. Rupturing Strain of Muscle and Tendon.

(a.) Dissect out the femur and gastrocnemius with the tendo Achillis of a
frog. Fix the femur in a strong clamp on a stand, preferably one with a
heavy base. To the tendo Achillis tie a short stout thread, and hang a scale-
pan on to it.

(b.) Place weights in the scale-pan, and note the weight required to rupture
the tendon or muscle. Usually the muscle is broken. The weight added will
be- 1 kilo., more or less, according to the size of the frog.

(c.) Compare the rupturing strain of a frog's gastrocnemius which has been
dead for forty-eight hours. A much less weight is required.

6. Dynamometers.

(a.) Hand. — Test the force exerted first by the right hand and then by the
left, by means of Salter's dynamometer.

(fc.)Arm. — Using one of Salter's dynamometers, test the strength of the
arm when exerted in pulling, as an archer does when drawing a bow.

7^0 PRACTICAL PHYSIOLOGY. [XXXIII.

LESSON XXXIII.

INDEPENDENT MUSCULAR EXCITABILITY — AC-
TION OF CURARE— ROSENTHAL'S MODIFICA-
TION—POHL'S COMMUTATOR.

1. Independent Muscular Excitability and the Action of
Cui'are. — Curare paralyses the intramuscular terminations of the
motor nerves. — Apparatus. — Daniell's cell, induction machine,
two keys, five vs^ires, shielded electrodes, scissors, fine-pointed
forceps, fine aneurism-needle, or fine sewing-needle fixed in a
handle, with the eye free to serve as an aneurism-needle, fine
threads, pithing-needle, i per cent, watery solution of curare,
hypodermic syringe or glass pipette.

(a.) Arrange the battery and induction machine for an inter-
rupted current with a key in the primary circuit, and a Du Bois
key to short-circuit the secondary, as in Lesson XXXI. 2.

(h.) Destroy the brain of a frog, and by means of a hypodermic
syringe or a fine glass pipette inject into the ventral or dorsal
lymph-sac two drops of a i p.c. watery solution of curare. [The
curare of commerce is only partly soluble in water, but its active
constituent curarin is. Rub up i gram curare in loo cc. water
and filter]. The poison is rapidly absorbed. At first the frog
draws up its legs, in a few minutes it ceases to do so, and will lie
in any position in which it is put, while the legs are not drawn up
on being pinched, and the animal lies flaccid and paralysed.

(c.) Expose the heart, and observe that it is still beating.

{(L) Expose one sciatic nerve.

(i.) Stimulate the sciatic nerve with interrupted shocks (faradisa-
tion) ; there is no cmitradion.

(ii.) Apply the electrodes to the rmisde-f ; they contract.

Tlierefore curare has paralysed some part of the motor nerves, hut
not tlie muscles.

In curare poisoning the nerve-trunk itself is not inexcitable, but
the nerve-endings in the skeletal muscles are so aff"ected, i.e.,
paralysed, as to prevent the excitatory state of the nerve being
propagated from the nerve to the muscle. The following experi-
ment proves this : —

2. On what Part of the Motor Nerve does Curare Act?

(a.) Induction apparatus as in the previous experiment,
(b.) Destroy the brain of a frog. Expose the sciatic nerve and
the accompanying artery and vein on one side, e.g., the left, taking
great care not to injure the blood-vessels. Isolate the sciatic

XXXIII.] INDErENDENT MUSCULAR EXCITABILITY. I9I

nerve, and then tie a stout ligature round all the other structure.s
of the thigh. In this way none of the poison can pass by a col
lateral circulation into the parts helow the ligature.

(('.) Inject a few drops of a i p. c. solution of curare into the
ventral lymph-sac. The poison will be carried to every part of the
body except the left leg below the ligature. The animal is rapidly
paralysed (20-30 mins.), but if the non-poisoned leg (left) is
pinched, it is drawn up, while the poisoned leg (right) is not, i.e.,
there is a reflex movement of the non-poisoned limb, so that the
afferent (sensory) nerves, spinal centre and motor nerves are still-
unaffected.

(if.) "Wait until the animal is thoroughly under the influence of
the poison, i.e., when all reflexes cease, and then expose both sciatic
verves as far up as the vertebral column and as far down as the
knee.

(i.) Stimulate the ririht sciatic nerve. There is no contraction.
Therefore the poison has acted either on nerve or muscle.

(ii.) Stimulate the rigid gastrocnemius muscle ; it contracts.
Therefore the poison has acted on some part of the nervous path,
but not on the muscle.

(iii. ) Stimulate the Ifft sciatic aitore the liriature ; the left leg
contracts. The part of the nerve above the ligature was supplied
with poisoned blood, so that the nerve-trunk itself is not paralysed,
as may be proved by stimulating any part of the left sciatic as far
down as its entrance into the gastrocnemius. Stimulating any
part of the left nerve causes contraction. Therefore neither
nerve-trunk nor muscle is affected. The nerve-impulse is blocked
somewhere, in all probability by paralysis of the terminations of
the motor nerves within the muscle.

(p.) Apply several drops of a strong solution of curare to the left
gastrocnemius, and after a time stimulate the left sciatic nerve ;
there is no contraction, but on stimulating the muscle itself con-
traction takes place.

The independent excitabiUty of muscle is further proved by
other experiments, all of which we owe to W. Kiihne.

(i) The Sartorius experiment (p. 191).

(2) Kiihne's Curare experiment (p. 194).

(3) The Gracilis experiment (Lesson L.).

3. Kiihne's Sartorius Experiment.

(a.) Isolate the sartorius (flg. iii) by the method given at
p. 186. Suspend the muscle by the thread tied around its tibial
attachments, I.e., with its iliac end downwards.

{b.) Allow the iliac end to dip into a drop of pure glycerin
placed on a greasy surface. The muscle gives no response. Why ?

192

PRACTICAL PHYSIOLOGY.

[xxxiii.

Because it is devoid of nerve-fibres. Then cut across the muscle
about 4 mm. higher up and dip the fresh transverse section into
the glycerin. Soon the muscle twitches. Why? As glycerin
stimulates nerve and not muscle, there is no response until the
glycerin is eitlier directly applied to nerve-fibres, or is difi'used
so as to aft'ect them

Kiihne used this experiment to demonstrate the independent
excitability of muscle and nerve.

4. Comparative Excitability of Muscle and Nerve.

(a.) Prepare a frog as for the curare experiment, i.e., ligature
one leg all except the sciatic nerve on that side, then inject curare
into a lymph-sac. After tlie curare has acted, expose both sciatic
nerves and both gastrocnemius muscles.

{h.) Note the approximation of the secondary coil to the primary
required to obtain a mechanical response or contraction to —
(i.) Single make induction shocks,
(ii.) Single break induction shocks,
(iii.) Faradisation.

When the electrodes are applied to the sciatic nerve of the
ligatured limb, i.e., the protected side, tabulate the results.

(e.) Apply the electrodes directly to the gastrocnemius muscle
of the opposite side, i.e., the poisoned limb, which is practically
nerveless, as curare paralyses the terminations of the motor nerves.
It will be found that a stronger shock is required to cause the
muscle to contract than is necessary through the intervention of
tlie nerve, i.e., muscle is less excitable than nerve.

Direct Stimulation of
Nerveless Muscle.

Distance of Primary from
Secondary Coil iu cm.

Stimulation of Nerve of
Lijjatured Limb.

M.

B.

M.

B.

0
0

0

c

OOOO

22
21
20
19

30
29
2S
27

0 C

0 c
0 c
c c

Faradisation.

Nerveless Muscle.

Distance of P from S.

Ligatured Limb.

0

35

c

0

34

G

0

33

C

0

32

C

XXXIII.] INDEPENDENT MUSCULAR EXCITABILITT. 193

5. Pohl's Commutator (fig. 113) is used for sending a current
along two different pairs of wires, or for reversing the direction of
the current in a pair of wires. It consists of a round or square
wooden or ebonite block with six cups, each
in connection with a binding screw. Between
two of these stretches a bridge insulated in
the middle. The battery wires are always
attached to the cups connected with this
(i and 2). When it is used to pass a current
through different Avires, the crot-s-bars are ®,

*^ , , . A 1 1 i. 11 • I'lO- 113.— Pohl's Conmiu-

removed and wires are attached to all six cups, tutor with Cross-bars.
3 and 4, 5 and 6. On turning the bridge

to one side or other, the current is sent through one or other pair
of wires. To reverse the direction of a current, only one pair of
wires, besides the battery wires, is attached to the mercury cups,
e.g., to J and 4, or 5 and 6, the cross-bars remaining in.

ADDITIONAL EXERCISES.

6. Curare and Rosenthal's Modification.

(a.) Prepare a frog as in the previous experiment, ligature the left leg— all
except the sciatic nerve— and inject curare. After complete paralysis occurs,
dissect out both legs with the nerves attached. Attach straw flags ( NP and P)
of diflerent colours to the toes of Loth legs by pins, and fix both femora in
muscle-forceps (F) with the gastrocnemii uppermost (fig. 114). Place the
nerves (N) on the platinum points of Du Bois-Reymond's electrodes (fig. 98).

(6.) Arrange the induction apparatus as in fig. 114, connecting the
terminals of the secondary coil with the jiiers of a Pohl's commutator (fig. 113)
without crossbars 'H). Two other wires jiass from two other binding screws
of the commutator to the electrodes (N), while two thin wires pass from the
other two binding screws (C), and their other ends are pushed through the
gastrocnemii muscles. The commutator enables the tetanising currents to be
passed either through both nerves or both muscles. It is more convenient
if the secondary circuit have a key, so that it may be short-circuited when
desired.

(i.) Set Neef's hammer going, and turn the handle of the commutator so
that the current passes through both nerves ; only the non-poisoned leg (NPj
contracts.

(ii.) Reverse the handle and j)ass the current through both muscles; both
contract.

(iii. ) Rosenthal's Modification.— Push the secondary spiral faraway fiom
the primary, and pass the current through both muscles. At first, if the coils
be sufliciently far apart, there is no contraction in either muscle. Gradually
push up the secondary coil, and notice on doing so that the non-poisuned
liwb contracts first, and that, on continuing to push up the secondary coil,
both muscles ultimately contract.

7. Action of Curare — Bernard's Method. — Prepare two nerve-muscle pre-
parations, and dip the nerve of one (A) and the muscle of the other (B) into a

N

194

PRACTICAL PHYSIOLOGY.

[XXXlV.

soli-tion of curare in two watch-glasses. On stimulating the nerve of A, its
muscle contracts ; on sLimulatiiig the nerve of B, its muscle does not contract,

but the muscle contracts when it is
stimulated directly. In A, although
the poison is applied directly to the
nerve-trunk, the nerve is not para-
lysed.

8. Kiihne's Curare Experiment.

— (rt.) To the margin of a meat-plate
fix two copper slips, to serve as
attachments for the electrodes, and
between the copi)er terminals place
a strip of filter- paper moistened with
normal saline.

(6.) Excise the sartorius of a large

frog, and cut it transversely into

five pieces of nearly equal length.

Place them in their original order

on the filter-paper, inunbering them

I to 5, Pass a feeble tetanising

current through the muscle, and

note that the central parts, i.e., 2,

3, and 4, contract, while i and 5

remain quiescent. On making the

current stronger the terminal i)arts

also contract. Why ? Because

Fio. ii4-S^;liemeof the Curare Experiment. t],pj.e ^le no nerves at the end of

s1;iral?rkeiVesfK f^'amp ; ^^"^0^.^ the sartorius and in the first instance

poisoned leg; P. Poisoned leg; C. Com- the muscular fibres are really excited

mutator ; K. Key. The shore-circuiting \)j stimulation of the intramuscular

the to'^am """''^""^ "''''"*'' *' """"^"^ '" terminations of the nerves, while in

the case of the end parts of the
divided muscle the muscle was stimulated directly.

(c.) If a curarised sartorius be experimented on in the same way all the
parts contract at once, because all the motor nerves in the muscle are para-
lysed.

LESSON XXXIV.

THE GRAPHIC METHOD -MOIST CHAMBER-
SINGLE CONTRACTION.

1. Recording Apparatus. — L'^se a revolving brass cylinder or
other moving surface covered with smoked glazed paper. The
velocity of the moving surface is usually determined by recording
simultaneously the vibrations of a tuning-fork of known rate of
vibration, or an electro-magnetic time-marker, or by a vibrating
veed (p. 211). It does not matter particularly what form of

XXXIV.]

THE GRAPHIC METHOD.

195

recording drum is used, provided it moves smoothly and evenly,
and is capable of being made to move at different speeds as required.
In Hawksley's form of drum this is accomplished by placing the
drum on different axles, moving at different velocities. In Ludwig's
form (fig. 115) this is done by moving a small wheel, n, on a large
brass disc, I). Where a number of men liave to be taught at
once, one must have recourse to an arrangement of shafting,
moved, say, by a water-motor or turbine, from which several
drums can be driven by cords. Or one may use a small gas-
engine as the motive power, and cords passing over pulleys to

Fio. 115. — Ludwig's Revolving Cylinder, R, moved by the clockwork in the box A, and
remilate(i liy a Foucault's regulator on the top of the l)ox. The disc D, moved liy
the clockwork, presses upon tlie wheel n, wliich can be raised or lowered by the
screw L, thus altering the position of n on D. so as to cause tlie cylinder to rotate
at different rates The cylinder itself can be raised by tlie handle U. On the left
side of tlie fl:.;ure is a mercurial manometer.

move the drums. This is the arrangement adopted in the Physio-
logical Department of Owens College, so that a number of men
can work at the same time, each being provided with recording
apparatus for himself. The Thirlemere water-motor may also
be used for actuating a number of recording cylinders.

2. Fixing and Smoking the Paper. — The paper is glazed on
one surface, and is cut to the necessary size to suit the drum.
The drum can be removed from the clockwork or other motor

196 PRACTICAL PHYSIOLOGY. [XXXIV.

which moves it, and is then covered with a strip of paper, the
latter being laid on evenly to avoid folds, glazed side outermost.
One edge of tlie paper is gummed, and slightly overlaps the
other edge. Leave it for a few minutes until the gum dries. The
paper has then to be blackened, by holding the drum and keeping
it moving over a fan-tailed or bat's wing gas-burner, or paraffin
lamp — the former is preferable. Take care that the soot from
the flame is deposited evenly and lightly, and see that it is not
burned into the paper. The drum is then placed in position in
connection with its motor. (See Appendix.)

To obtain a very fine film of soot, Hiirthle has invented a "smoke-spray."
The soot from the flame of a turpentine lamp is blown by means of an
elastic ball-bellows against the paper.

3. General Rules for Graphic Experiments.

(i.) Arrange the apparatus completely, cover the drum with
paper, and smoke it, before beginning the dissection.

(2.) Test all the connections stage by stage as they are made.

(3.) Each tracing is to be inscribed with the name of the
individual who made it, the date, what it shows, and then it
is varnished.

4. Myographs. — Various forms are in use, but most of them
consist of a light lever which is raised by the contracting muscle,
and so arranged as to record its movement on a smoked surface of
paper or glass. Such curves are called " isotonic " by Fick. The
movements of the muscle are thereby magnified and rendered
visible to the eye. Or the lever may record its movements on a
moving surface. Taking advantage of the fact that a muscle wdien
it contracts becomes both shorter and thicker, myographs have
been constructed on three principles : —

(a) Shortening of muscle attached to a lever.
(/3) Thickening of muscle on which the lever rests.
But suppose a muscle to be so fixed that during activity it cannot
contract, then we have changes in tension, so that we can record
cliangesof tension by the so-called "isometric " method introduced
by Fick (Lesson XXX VL).

(y) Changes in tension.
The recording surface on which the style of the lever writes may
be—

(i.) Stationary (Pjlu//er's).
(2.) Rotatory (Hehnholt ■:'.■<).
(3.) Swinging pendulum (F/rk'>>).

(4.) Moved from side to side by a spring, either vertically (Du
Buia-ReymoHd) or horizontally.

XXXTV.]

T.RE CPAPHTC MTTHOB.

197

5. Muscle-Lever (change in length of muscle). — It is customary
to use such a muscle-lever as is shown in fig, 116, with the weight
attached directly under the point of attachment of the muscle to
the lever. This has its disadvantages, as it is set into vibration by
the rapid rise of the lever. Fick has shown that by using a light
straw lever, the muscle itself being made tense not by a weight
applied directly under the point of attachment of the muscle to
the lever, but by attacliing the weight over a small pulley fixed
to the steel axis to which the lever is attached, by this arrange-
ment the weight is raised but little, and even with a rapid con-
traction does not move quickly.

Fig. 116.— Moist Cliamber. N. Glass shade: E. Electrodes; L. Lever; W. Weight;
TM. Time-marker ; other letters as in previous figures.

6. Moist Chamber (fig. 116). — To prevent a preparation from
getting dry, enclose it in a moist chamber, which is merely a glass
shade placed over the preparation. To keep the air and the pre-
paration moist, cover the sides of the shade with blotting-paper
moistened with normal saline.

7. Varnish for Tracings. — The tracing is drawn through the varnish and
then hung uji to di y.

(a.) A good varnish consists of gum mastic or white shellac dissolved to
saturation in methylated s]>irit.

(6.) Where a large quantity is used, and economy is an object, gum juniper
may be used instead of mastic.

<c.) Dissolve 4 oz. of sandarac in 15 oz. of alcohol, and add half an oz. of
chloroform,'

8. Single Contraction or Twitch.— Apparatus. — Recording
drum, Daniell's cell, Hg-key, induction coil, Du Bois key, wires,

198 PRACTICAL PHYSIOLOGY. [XXXIV.

electrodes, moist chamber and lever (or crank-myograpli), moist
blotting-paper, stout ligatures, hook, pins, lead weight (20 grams).

(a.) Cover the drum with glazed paper, smoke it, and arrange it
to move slowly.

(h.) Arrange the apparatus: — Daniell's cell' and a mercury key
in the primary circuit, the secondary circuit short-circuited, and
with wires going to the binding screws on the platform of the
moist chamber on the myograph (fig. 116). [The muscle may be
caused to contract either by stimulating it directly, in which case
the electrodes are made of thin wires, and merely pushed through
the two ends of the gastrocnemius, or indirectly through the nerve.
It is convenient to use the latter method (Lesson XXXII.).]

(c.) Make a nerve-muscle preparation, leaving the lower end of
the femur in connection with the gastrocnemius, and cut away the
tibia and fibula. With the point of a sharp pair of small scissors
make a small hole in the tendo Achillis, and insert in it an S-shaped
hook, made by bending a pin. Arrange the preparation in the
moist chamber by fixing the femur in the muscle clamp, and by
means of a stout thread attach the hook in the tendo Achillis to
the writing-lever. See that the muscle or ligature goes clear
through the hole in the stage, and that the hook does not catch on
anything. Place the nerve over the electrodes, and cover the whole
preparation with the glass shade lined on three sides with moist
blotting-paper. Load the lever either directly or by means of a
scale pan near where the muscle is attached to it by a weight of
about 20 grams, and make the lever itself write horizontally on the
cylinder. The writing-style on the tip of the lever may be made
of very thin copper foil or parchment paper, fastened to the lever
with sealing-wax or telegraph composition.

As here arranged the primary circuit is made and broken by
hand.

According as the recording surface is stationary or moving
when the muscle contracts and raises the lever, either an upward
line or a curve will be made upon the paper. In the latter case
the form of the curve will vary with the velocity of the drum.

A. Simple twitch with the recording cylinder stationary.

By tliis arrangement one registers only the Kft or height of the
contraction, and its relation to the strength of the stimulus ;
yielding minimal and maximal contractions. A light (isotonic)
lever is chosen, such as will amplify the movement 6-8 times,
while the weight to be lifted is such that the tension of the
muscle is about 8-10 grams.

(a.) Push the secondary coil away from the primary, open the
key in the secondary circuit, and make and break the primary

XXXIV.] THE GRAPHIC METHOD. 199

circuit. There may be no contraction at either M. or B. Close
the secondary circuit key.

(b.) Open the short-circuiting key, gradually push up the secondary
coil, and break the primary circuit by means of the key in it.
Observe when the first feeble single contraction or twitch is
obtained = minimal contraction. Make the primary circuit, there
is no contraction. The break shock is drow/<'r tlian i/ie make.
Record under each contraction whether it is a make (M.) or break
(B.) shock, and the distance in centimetres of the secondary from
the primary coil. The minimal contraction may first be obtained
when the secondary coil is 35-40 cm. from the primary. jSIove
the drum a short distance with the hand ; the lever inscribes a base
line or abscissa.

(c.) Push up the secondary coil .5 cm. at a time. Test the effect
of the make and break shocks, after each test moving the cylinder
with the hand, and recording the result as to M. or B., and the
distance in centimetres of the secondary from the primary coil.
After a time a i^I. contraction appears, and on pushing up the
secondary coil the M. contraction becomes as high as the B.
(fig- 117)-

Fia. 117. — Contractions obtained with make (M.) and break (B.) induction shocks. The
numbers indicate the distance of the secondary from the primary coil. The cylinder
is stationary during each contraction and is then moved a little distance by band.

(rf.) Increase the stimulus by bringing the secondary nearer
the primary coil, and notice that the contractions do not become
higher = maximal contraction. In each case keep the M. and
B. contractions obtained with each strength of current close
together. Their relative heights can then be readily compared
(fig. 117).

B. Twitch with Cylinder revolving (fast speed). — Arrange
the experiment as in A, but allow the cylinder to revolve about
50 centimetres per second.

(a. ) Select a strength of stimulus (break shock only) which is
known to cause a contraction, and while the cylinder is revolving,
cause the muscle to contract.

200

PRACTICAL PHYSIOLOOy.

[xxxv.

(h.) Study the muscle-curve obtained, a so-called " isotonic "
curve (fig. i2i).

C. Vary the velocity of the cylinder, and observe how the
form of the curve varies with the variation in velocity of the
cylinder (fig, ii8). Use only the break shock, and record the

contractions either (i.)
all on one abscissa, or
(ii.) record each con-
traction on a different
abscissa, recording a
time-curve under each
(Lesson XXXV.).

D. Remove the trac-
ing's and varnish them.

FlO. ii3— Fi-og's Gastrocnemius Stinmlateil by ;i Single
Millie (il.) and Break (B.) Sliock, tlie distance between
the primary and secondary coil being the same for both
shocks. In the lower tigure the muscle was somewhat
fatigued. Slow rate of speed.

9. Relation of
" Lift " to Strength of
Stimulus. — Suppose
one uses only break shocks, and, beginning with the first effective
stimulus (" Minimal Contraction ") and gradually increasing the
strength of the stimulus, one obtains a gradual increase in the height
of the " hft " until a certain maximum of hft (" Maximal Con-
traction-") is reached, above which, even though the stimulus be in-
creased, there is no further shortening of the muscle. If a muscle
be stimulated directly (i.e., the electrodes applied to the muscle
direct), the difference between the first effective stimulus (minimal)
and the first effective maximal stimulus is considerably greater than
by indirect stimulation (i.e., when the stimulus is applied through
the nerve).

LESSON XXXV.

CRANK-MYOGRAPH— AUTOMATIC BREAK.

Instead of the muscle-lever shown in fig. 1 1 6, very frequently the
crank-myograph is used (fig. 1 1 9). The muscle placed on it can
be kept moist by a cover of blotting-paper moistened with normal
saline.

1. The Crank-Myograph (fig. 119) is fixed on a suitable sup-
port, so that it can be adjusted to any height desired.

After-Load. — In the crank-myograph, under the lever, is a
screw on which the horizontal arm of the bell-crank rests (fig. 119,

XXXV."!

CRANK-MYOGRAPH.

201

a), so that the muscle is loaded only during its contraction. Thus
a muscle may be " loaded '' or " after-loaded " ; in the former case,
the muscle is loaded with a weight, both when it is at rest and
when contracting, but in an " after-loaded " muscle the muscle
raises the weight only during contraction, and is not stretched by it
when at rest. The experiment is arranged in the same way as in
Lesson XXXIV. 8.

(a.) Make a preparation of the gastrocnemius with the lower end
of the femur attached. Pin the femur firmly to the cork plate of
the myograph covered with blotting-paper moistened by normal
saline. Tie a stout Ugature round the tendo Achillis, by a hook fix the
ligature to the short arm of the lever, add a weight of 10-20 grams
to the lever, and see that the lever itself is horizontal. Thrust two
fine wires — which act as electrodes — from the Du Bois key in
the secondary circuit througli the upper and lower end of the
gastrocnemius muscle.

FlO. iio.— Crank-Myograph. W, W. Block of wood ; 31. iluscle : F. Femur; P. Pin to
fix F; L. Lever ; WT. Weight ; a. Screw for after-load ; C. Cork ; B, B. Brass box.

{b.) Arrange the style of the lever so that it writes on the
cylinder, and repeat, if desired, the experiments of the previous
Lesson.

(c.) Use different weights — 5 — 20 — 50 grams — and observe how

the form of the curve
the lever.

varies on increasing the weight attached to

2, Automatic Break, i.e., Method of Excitation. — It is con-
venient to use a single break induction shock, i.e., the secondary
coil is at such a distance from the primary that only the break shocK
is effective. One may, of course, break the primary circuit by the
hand, as in the previous experiments, but this is not convenient
It is better to have an " automatic break" (fig. 120) done by the
drum itself as it revolves, the drum being introduced into the
primary circuit. Two binding screws are placed on the stand, but

202

PRACTICAL PHYSIOLOGY.

[xxxv.

one is insulated. The axis of the drum carries a horizontal (adjust-
able) arm or " striker " carrying a platinum wire which touches a
wire fixed on a support on the insulated binding screw. Thus every
time the drum revolves a shock is induced, and always at the same
moment, so that successive shocks can be recorded on the same
abscissa and the moment of stimulation can be found at once,

3. Simple Muscle-Cui-ve with Crank-Myograph and Automatic
Break. — Apparatus required.— (1) Eecording drum moving at a
fast rate (about 50 cm. per second) ; (2) crank-myograph ; (3)
chronograph vibrating 100 times per second ; coil ; keys.

Fig. 120. — Arrangement fur analysis of Muscle-Curve by means of Crank-Mj'ograph (3f)
with " Automatic Break " Arrangement in Primary Cii'cuit. S. Striker on axis of D
cylinder; P.C. Primary, and S.C. Secondary circuits; T.C. Time-circuit with E.M.
Electro-magnet ; I.S. Insulated support in P.C.

(a.) Arrange the apparatus as in fig. 120. The cylinder (D) is
placed in the primary circuit. When the horizontal arm or striker
(S) fixed to the vertical spindle touches the upright, the primary
circuit is made and broken and induction shocks are induced in the
secondary circuit. Select a break shock, i.e., when the make is not
yet effective. The vertical support (I.S) is insulated from the
base of the drum support.

(h.) Short-circuit the secondary current, arrange a nerve-muscle
preparation on a crank-myograph (M), place the nerve on the

XXXVI.] ISOTONIC AND ISOMETRIC CONTRACTIONS. 203

electrodes, arrange the weighted writing-lever to write on the
drum.

(c.) Arrange the lever of a chronograph (viliratijig loo times per
second and actuated by a Grove's cell in circuit with a tuning-fork,
T.C time-circuit) so that the one writing point records exactly
under the other.

Make base lines and ordinates — muscle-lever and time-lever —
on the cylinder to mark the relative positions of the two writing
points, or cause one to write exactly over the other.

(d.) Adjust the position of the break key in order to have the
tracing near the middle of the paper and not near where it is
gummed. Open the short-circuiting key, set the chronograph
vibrating, and the cyhnder in motion during one revolution. When
the striker (8) comes in contact with support (I.S) a break
induction shock is obtained, and the muscle records a simple muscle-
curve. Close the short-circuiting key.

(c.) Record the moment of stimulation by bringing S into contact
with the style on I.S. The distance between this point and the
beginning of the curve indicates the latent period.

(/.) Study the "muscle-curve" (fig. 121), noting particularly
the latent period, the ascent and descent. The latent period may
be represented by a distance of 4 or 5 millimetres, but this delay
does not represent the actual latent period, which is really much
shorter. The long latent period is really largely due to the
apparatus and therefore instrumental. Estimate, by means of the
tuiiing-fork vibrations, the duration of each of the phases.

LESSON XXXVL

ISOTONIC AND ISOMETRIC CONTRACTIONS-
WORK DONE— HEAT-RIGOR.

1. Isometric v. Isotonic Contraction (Eick). — In the ordinary
way of recording a simple muscular response or twitch, as just
described, a light lever (with a light weight attached) records its
movements, so that the muscle is constantly stretched by and con-
tracts against a small constant resistance during its contraction.
Such a curve is isotonic (fig. 121).

If, however, the muscle contracts by pulling on a strong spring of
great resistance, — such a spring, for example, as requires about 500
grams to bend it slightly, — then the curve obtained is isometric.
The curves obtained by cUnical dynamometers are of this class.

204

PRACTICAL PHYSTOLOGY.

fxxxvi

For isometric curves Fick attached a muscle to the short arm of a lever, the
other arm being prevented from moving much by the resistance of a strong
spring. In this way one obtains a curve, which shows little change of form,
but indicates the increase and decrease of tension during the contraction, the
length of the muscle remaining nearly constant, and for this reason Fick
called it " isometric." Of course an absolutely isometric curve cannot be
recorded.

Fig. 121.— Muscle-Curve of Frog s Gastrocnemius. The lower line indicates time,
and each double vibration (D. F.)=^H„ sec.

If one compares an isotonic and isometric curve from the same muscle, one
finds that the apex of the isometric curve lies nearer the beginning of the
contraction than that of the isotonic curve, i.e., the length remaining the
same, the isometric curve reaches the maximum of its tension sooner than it,

the tension being the same,
reaches the maximum of its
shortening. Moreover, the iso-
metric curve is Hat-topped, so
that it remains for some time in
contraction (fig. 122).

FiQ.

Diagram of isotooic, b, isometric
muscle-curves.

2. Registration of Ten-
sion of a Muscle (Fick). —
When the two ends of a
muscle are so fixed that
during activity they cannot
approximate towards each
other, then the muscle does
but only its tension. Fick calls this an

not change its length
" isometric " method.

One can record the change in tension by means of a

tension-

XXXVI.] ISOTONIC AND ISOMETRIC CONTRACTIONS. 205

recorder" devised by Fick (tig. 123). One end of the muscle is
fixed, the other is attached by means of an inextensible thread
wliich passes round a small pulley fixed on a steel axis (A). This
axis carries (i) a long light recording lever (Z), and (2) a hori-
zontally placed steel spring (F) whose free end rests on a support
(;<). When the muscle contracts, the spring (F) is pressed against
the support {u). In consequence of the opposing tension of the
spring the axis can only be turned slightly, but this movement is
greatly amplified by the recording lever.

Schonlein has devised a myograph {Pfluger's Arddv, Ed. 52, p.
112), which is so arranged that one can record either isotonic con-
tractions or isometric contractions. The isometric curves so
obtained have been called " tonograms." The apparatus Is made
by W. Siedentopf in Wiirzburg.

3. Work Done during a Single Contraction. — Arrange a gastroc-
nemius to record on a cylinder, but record only the " Hft," as in

F

T?

Fig. 123.— Scheme of Kick's Tension-recorder. A. Axis movement; F. Strong spring
resting on support v, : Z. Writing-lever.

Lesson XXXIV., the cylinder being stationary, moving the
cylinder with the hand as required. On the lever under the
muscle attachment place a scale-pan, and in this place weights of
known value. With each twitch the muscle lifts the weight, and
thus does a certain amount of work which is easily calculated

{11) Measure the height of the tracing from the base line or
abscissa. This is conveniently done by a paper millimetre scale
fixed to a microscopic shde. The work done (W) is equal to the
weight {iv) lifted multiplied by the height (//) to which it is lifted —

W = ich.

But, of course, a long lever being used, the tracing is much higher
than the actual shortening of the muscle.

{h.) To determine the exact amount of the lift, one must know the
length of the lever and the ratio between its arms. Suppose the
one to be ten times as long as the other, then the total work in
gram-millimetres must be divided by 10.

2o6

PRACTICAL PHYSIOLOGY.

[XXXVII

('•.) To determine the greatest amount of work obtainable,
various heights must be tried to get the largest product, care
being taken not to fatigue the muscle.

4. Curve of Heat-Rigor. — (n.)
Arrange a frog's gastrocnemius to
record by means of a crank-myo-
■^raph on a slow-revolving drum,
weighting it with 30-50 grams.
Inscribe the continuous change of
form of the muscle produced by
pouring water at 70' C. on the
muscle.

(b.) Or, use the following appa-
ratus devised by Ludwig, where,
however, the sartorius is used in
place of the gastrocnemius, as it
has parallel fibres (fig. 124).

5, Chordogram. — Engelmann
(Croonian Lecture, R. S. 1895) has
shown that, when a short length
(S cm.) of an E violin string, pre-
viously swollen in water, is fixed
so as to record any alteration in
its length, on suddenly heating the

¥iQ. 124. -Apparatus for obtaining the curve string the lever rises, and on cool-
of a sartorins in heat-rigor. ing the lever falls and a curve is

recorded just like a contraction
curve of muscle. Or a string may be made to swell by dijiping in hot water
and then soaking in concentrated glycerin. This can then be heated in air
and the movements recorded.

LESSON XXXV n.

PBNDULUM-MYOGRAPH— SPRING MYO GR A PH—
DESPRETZ SIGNAL.

1. Penduhim-Myograph Muscle-Curve.

(a.) Cover the oblong glass plate with glazed paper, smoke its
liurface, and fix it to the pendulum. The plate must be so adjusted
that the pendulum, on being set free from the "detent" (fig. 125,
C), shall be held by the " catch " (C). Test this.

{/).) Arrange the primary circuit for single shocks as in fig. 125,
interposing tlie triggor-key or knock-over key of the pendulum-
myograph (K'). Short-circuit the secondary coil.

(c.) Fix the femur of a nerve-muscle preparation in the clamp,
attach the tendo Achilhs to the writing-lever (S), and place the

XXXVII.]

PENDULUM-MYOGRAPH.

207

nerve over the electrodes in a moist chamber or use a crank-myo-
graph. Load the lever with 20 grams, and direct its point to the
side to which the pendulum swings. Fix the pendulum with the
detent, and adjust the writing-style of the lever on the smoked
surface. Connect the electrodes (or wires) from muscle or nerve to
the short circuiting key
in the secondary circuit
(omitted in fig. 125).

After opening the
secondary circuit, with the
hand break the primary
circuit to make certain
that the muscle responds
at break.

('/.) Close the trigger-
key (K') in the primary
circuit, and open the key
in the secondary circuit.
Allow the pendulum to
swing ; as it does so, it
knocks over the key in
the primary circuit and
breaks the current, thus
inducing a shock in the
secondary circuit, whereby
the muscle is stimulated and
caused to record its con-
traction or muscle-curve
on the smoked surface.

(e.) Abscissa, i.e., the base line. Rotate the stand supporting
the muscle to remove the writing point of the lever from the
recordhig surface. Bring the pendulum back to the detent, adjust
the writing-style, close the trigger-key, and keep the secondary cir-
cuit short-circuited. Allow the pendulum to swing. This records
the base Hne.

(/.) Latent period.— Bring the pendulum to the detent, short-
circuit the secondary circuit, and withdraw the writing-style as in
(e.). Close the trigger-key, with a finger of the left hand keep it
closed, allow the lever to touch the glass plate in its original posi-
tion, and with the right hand bring the knife-edge of the pendulum
in contact with the trigger-key, so as just to open it. A curved
line is inscribed on the stationary plate, which indicates the moment
of stimulation.

(g.) Time-Curve. — Remove the muscle-lever, place the pendulum
in the detent, close the trigger-key, take a tuning-fork, vibrating,

Fia. 125. — Sclieiiie of the Arrangement of the Pen-
dulum. £. Battery; /. Primary, //. Secondary
spiral of the induction machine; S. Tuoth ; K'.
Key ; C, C. Catches ; K' in the corner. Scheme of
K' : E. Key in primary circuit. It is well to have
a short circuiting key in the secondary circuit.

208

PRACTICAL PHYSIOLOGY.

[XXXVII.

say, 1 20 or 250 double vibrations per second, and adjust its
writing-style in the position formerly occupied by the style of the
muscle-lever. Set the fork vibrating, either electrically or by
striking it. Allow the pendulum to swing, when the vibrating

250 DV.

Fig. 126. — Pendulum-Myograph Curve. S. Point of stimulation ; A. Latent period ;
£. Period of shortening, and C. of relaxation.

tuning-fork will record the time-curve under the muscle-curve (fig.
126, 250 DV). All the conditions must be exactly the same as
when the muscle-curve was taken.

Pig. 127. -Spriug-Myograph.

(/).) Varnish the curve, and measure its phases. Bring ordinates
vertical, a, 0', c', to the abscissa, and measure the " latent period "
(fig. 126, A), the duration of the shortening (B), the phase of
relaxation (C), and the contraction remainder.

2. Spring-Myograph (fig. 127). — The arrangements are exactly

xxxvir]

PENDULtJM-MYOGRAPH.

209

fix it with the
tlie trigger key

the same as for tlie peiuIuUini myograph, the trigger-key of the
myograph being placed in the primary circuit.

(a.) Cover the glass with glazed paper, smoke it, and fix it in
the frame. Push the plate to
one side, and
catch. Close

(b.) ^lake a nerve-muscle
preparation, and arrange it to
write on the glass plate. Open
the secondary circuit.

(r.) Press on the thumb-
plate (a), thus lil)erating the
spring, when the glass plate
shoots to the other side, when
the tooth ((/) on its under
surface breaks the primary
circuit, and the muscle-curve
is recorded.

(d.) Short-circuit the second-
ary circuit, push back the
plate, and fix it Avith the
catch ; close the trigger-key,
and si loot the plate again to
record the abscissa.

(e.) Make a thue-ClU've. Push the plate back again, and fix it;
close the trigger-key — in order that the conditions may be exactly
the same as before — set a tuning-fork in vibration (120 double
vibrations per second), and adjust its writing-style under tlie
abscissa. Shoot the plate again, and recoi'd the time-curve.

Fig 123— -Anangeinent for Estimating the
Tiiiie-Kelatioiis of a Single Muscular Cnn-
tiaction. D. Battery ; A'. Key in primary
circuit ; /. Primary, //. Secondary coil,
without a sliort-circuitiiig key ; I. Muscle-
lever ; e. Electro-magnet in primary cir-
cuit; (. Electric signal ; St. Support; RC.
Revolving cylinder. Iiitrnduce a short-
circuiting key into the secondary circuit.

ADDITIONAL EXERCISES.

3. Study the iiu'ivoved form of this instnimeiit recently introduced by Du
Bois-Reyiuond in wliich the glass plate is set free, and the tuning-fork vibra-
tions ai'e recorded simultaneously when a handle is pressed. It has a simple
mechanism for adjusting the writing-styles for the muscle and abscissa.

4. Analysis of Twitch on a Kevolving Drum.

(«.) Arrange the drum to move at a fast speed (50 cm. per sec.)
(b.) Arrange an induction coil for single B. shocks, the secondar}' circuit
short-circuited, and arranged to stimulate a nerve attached to a muscle placed
in a moist chamber, or on a crank-myograjih, as directed for the foregoing
experiments. In the primarj' circuit introduce, besides the spring-key, an
electro-magnet with a marking lever (figs. 116, 128, e), and cause its point to

2IO

PRACTICAL PHYSIOLOGY.

[xxxvii.

■vi'vite exactly under the muscle-lever. Arrange, with its point exactly under
the other two, a Despretz chronograph or signal, in circuit with a tuning-fork
of known rate of vibration, and driven by means of a Grove's cell (fig. 129).
The three recording levers are all fixed on the same stand, which should

Fig. 129. — Signal and Vibrating Tuning-Fork in an Electric Circuit. D. Drum ;
C. Signal ; EM. Electric tuning-fork ; /"«. Platinum contact.

preferably be a tangent one, i.e., the rod bearing the recording styles can by
means of a handle be made to rotate so as to bring the writing-styles in con-
tact with the recording surface.

On opening the secondary circuit and breaking the primary one, the muscle
contracts, and at the same time the stjde of the electro-magnet is attracted
and records the exact moment of stimulation (fig. 116).

5. Despretz Signal (figs. 129, 130). — This small electro-magnet has so little
inertia that, if it be introduced into an electric circuit, its armature, which

Fig. 130.— dspretz Electric Signal or Chronograph, as made by the Cambridge
Scientific Instrument Company.

is provided with a very light writing ]ioint, vibrates simultaneously with
the vibrations of an electric tuning-fork introduced into tlie same circuit.
Arrange the signal and tuning-fork as in fig. 129. The drum must move
more rapidly, the more rapid the vibrations of the tuning- fork used. Use a

XXXVII.]

PENDULUM-MYOGRAPH.

211

Grove's cell. The analysis may also be done by means of the "automatic
break " arrangement attached to the revolving drum (Lesaou XXXV.).

J'lG. 131.- Clironograph arranged to "Write on * Hoi/^n'al Cylinder, as made by Verdln

Fig. 132.— Marey's Simple Myograph, as made by Verdin.
6. Vibrating Eeed as a Chronograph.— For measuring small intervals of
time this is very convenient. The arrangement was first adopted by Grun-

212

PRACTICAL PHYSIOLOGY.

[xxxvii.

mach, acting on the suggestion of Kronecker. A steel tongue, vibrating a
hundred times per second, covers an oblong aperture placed at the lower part
of a gradually-narrowing brass tube, closed at the narrow end. To the
tongue is attached a stylette, which records the movements of the former. To

'5 >,

5 5

OO

§■3

the open end of the brass tube of the instrument is attached a brass ball or
resonator, and to the latter a caoutchouc tube. When air is sucked through
the apj)aratus, the reed (and with it the stylette) is set vibrating. It may be
kept vibrating by means of an aspirator placed in connection with a water-
tap.

XXXVIir.] INFLUENCE OF TEMPERATURE, ETC. 213

7. Marey's MyogTapli(fig. 132).— The pithed frog is pinned on a cork plate,
the tendon of the gastrocnemius is dissected out and attached to a writing-
lever, wliich is weiglited with a counterpoise ; tlie sciatic nerve is dissected
out and stimulated in the ordinary way. The cylinder moves on a horizontal
axis. The muscle can be stimulated while it is still in silu, and is under
more normal conditions than in the case of an excised muscle. It is useful
for the study of the action of poisons on muscle.

8. Spring-Myograph of Fredericq (fig. 133V — Tliis is arranged in the same
way as the spring-myograph, but the glass plate is placed horizontally. The
glass plate is pulled along rapidly by a band of caoutchouc. A key in the
primary circuit is opened by means of a pin attached to the frame carrying
the glass plate when the j)late is discharged. In an improved form of the
instrument, a steel rod made to vibrate at tiie moment the plate is discharged
records a time-curve beside the muscle-curve.

LESSON XXXVIII.

INFLUENCE OF TEMPERATURE, LOAD, AND
VERATRIA ON MUSCULAR CONTRACTION.

1. Influence of Temperature on Muscular Contraction.

{a.) Arrange the nerve-muscle preparation on a crank-myograph
— after-loaded — as in Lesson XXXV., using the automatic key by
means of the drum. All tlie curves are thus taken on the same
abscissa. Take a tracing at the normal temperature of the room.
Mark the moment of stimulation.

Fig. 134.— Showing how the foim of a Muscle-Curve varies with tlie temperature of the
water flowing through the box, shown in fig. 119. i at 5° 0. ; 2 at 10°; -i at 15°;
4 at 20° ; 5 at 25° ; 6 at 30° ; 7 at 35° ; and 8 at 40° C. The lowest tracing indicates
time, 100 D.V. per second, x the moment of stiinulatiou, by automatic break.

(ft.) Place ice upon the skin over the gastrocnemius for some
time, or pour iced salt solution on the exposed gastrocnemius, and
then take another tracing on the same abscissa, noting the differences

214

PRACTICAL PHYSTOLOaV.

[XXXVIII.

in the result. The contraction is both much longer and lower, and
the latent period is also longer.

(f.) Pour on to the muscle warm salt solution and take another
tracing. Observe the result. Do not overheat the muscle or heat-
rigor results (fig. 134).

Other Methods. — [d.) Adjust a piece of wire gauze over the leg, and allow
it to project beyond the end of the jilate ot the myograph. Heat the gauze
with a spirit lamp. Take a tracing. The contraction is shorter than in 1
{h. ). Do not overheat the muscle.

(e. ) A piece of lead-piping of narrow diameter {^ inch) can be bent into the
form of a cylinder, and the muscle placed within it. 'W'ater of various
temperatures can then be passed through it.

(/. ) The muscle may be attached to an ordinary horizontal writing-lever.
Surround the muscle with a double-walled box, with an inflow and outHow
tube, through which water at ditfercut temperatures can be j)assed. A
delicate thermometer is ])laced in the chamber with the muscle.

{^g.) A convenient method is to allow the muscle to rest on a small circular
brass box, iitted into the wooden plate of the crank myograjih. The box (B,
B) is jirovided Avith an inflow and an outliow tube, througli which water of
the desired temperature can be passed.

leye£_only^

250 DV.

Fio.

-Pendulum Myograph Curves, showing the Influence of tlie Load on
the Form of tlie Curve.

2. Influence of Load on Form of Muscle-Curve.

(a.) Arrange an experiment with the pendulum-myograph as in
Lesson XXXVIL, using either a muscle-lever or a crank-myograph.
Or, arrange a crank-myograph (after-loaded) to write on a cylinder,
the cylinder being arranged to break automatically the primary
circuit as at p. 202. Take all the curves on the same base line.

{h.) Take a tracing with the muscle weighted with the lever
only.

(c.) Then load the lever successively with different weights (5, 20,
50, 70 . . . 100 grams), and in each case record a curve and observe
how the form of the curve varies (fig. 135).

{d.) In each case record the abscissa and time-curve.

3. Influence of Veratria on Contraction.

(a.) Destroy the brain of a frog, and inject into the ventral
lymph-sac a few drops of a i p.c. solution of sulphate of veratria.

XXXVITI.] INFLUENCE OP TEMPERATURE, ETC.

215

When the frog is under the influence of the drug, discharge a
reflex act by mechanically stimulating the skin of the leg. The
limbs are extended, and remain so for several seconds, due to the
prolonged contraction of the extensors overcoming the flexors
and thus causing extension of the legs.

(A.) Arrange the induction machine for single shocks to make
and break the primary circuit by the hand by means of a contact-

FiG. 136. — Muscle-Curve from a " Veratrised " Muscle, recorded on a Slow-moving
Drum. A. Abscissa ; T. Time in seconds.

key. Short-circuit the secondary. Do not stimulate the muscle
often, as the veratria eff"ect diminishes with acti^dty of the muscle.

(c.) Make a nerve-muscle preparation and fix it on a crank-
myograph. On dividing the spinal cord notice the prolonged
extension of the legs.

Arrange the muscle-lever to record its movements on a slow-
revolving drum (1-2 cm. per second). Take a tracing. Note that
the muscle contracts quickly enough, but the contraction is very
high compared with that of a non-poisoned muscle, while the

Fig. 137. — Veratria Curve (Upper). Normal Muscle-Curve (Lower). Quick-moving drum.

muscle relaxes very slowly indeed. The relaxation phase may
last several seconds, i.e., a kind of "contracture." Record half-
seconds or seconds under the tracing. The tracing may show an
uneven curve, due to irregular spasms of the muscular fibres, or an
initial contraction as in fig. 136.

(d.) Take a tracing with a quick-moving drum, and such a curve

2l6 PRACTICAL PHYSTOLOGY. [XXXIX.

as fig. 137 will be obtained, where the drum goes round several
times before the relaxation is complete.

(fi.) Note that, if the " veratrised " muscle be made to contract
several times, the effect passes off — only a simple twitch being
obtained — but is re-established after rest. A high temperature
also causes it to disappear.

(/'.) The direct action of veratria on muscular tissue may also be
stxidied by the apparatus described in Lesson XLIII., and by this
method it is easy to compare the form of the curve before and
after the action of the poison (fig. 137). The drum makes many
revolutions before the lever comes to the abscissa again.

(rj.) Investigate the effect of heat and cold in modifying the
curves obtained. Under heat the veratria influence passes off.

LESSON XXXIX.

ELASTICITY AND EXTENSIBILITY OP MUSCLE -
BLIX'S MYOGRAPH.

1. Extensibility and Elasticity of Muscle.

(a.) Dissect out the gastrocnemius of a frog with the femur
attached, fix the femur in a strong clamp, attach the tendon to a
muscle-lever with a scale-pan attached. Neglect the weight of the
pan, and see that the lever writes horizontally on a drum. It is
better to do the experiment with the sartorius (or with the semi-
membranosus and gracilis, Lesson XXIX.), as they have parallel
fibres.

(h.) Place in the scale-pan, successively, different weights (10,
20, 30, 40 . . . 100 grams). On adding 10 gram.s, the lever
descends ; remove the weight and the lever ascends. Move
the drum a certain distance (about 3°), and add 20 grams to the
scale-pan. This time the vertical line drawn is longer, indicating
greater extension of a muscle by a greater weight, but neveitheless
the muscle lever will rise to its original height on removing the
weight. Repeat this with other weights. With the heavier
\i eights see that everything is. securely clamped. If the apices of
all the lines obtained be joined, they form a liyperhola. The
muscle, therefore, has not a large amount of elasticity, i.e., it is
easily extended by light weights, and on removal of the weight it
regains its original length, so that its elasticity is said to be perfect.
The hi/jjerhola obtained shows further that the increase in length

XXXIX.] ELASTrCITY AND EXTK^TSIBTLTTY OF MUSCLE. 217

is not directly proportional to the weight, but diminislies as the

weights increase (fig. 138).

{'■.) Repeat the same experiment with a strip of india-ruhher.

In this case equal increments of weight give an equal elongation,
so tliat a line joining the apices
of the vertical lines drawn
after each weight is a slmiyhi
line (fig. 139).

2. The Extensibility cf
Muscle is Increased during
Contraction, its Elasticity is

Via. 133. — ciiive of Diminished. fig i^Q^curve of

Elasticity of a F.O.S ^^-^ j.^^ ^,^^ gastrocnemius- ^l^^'^''^'^-
or preferably semi-membranosus
and gracilis — in a strong clamp, connecting it to a lever to record
on a drum, and adjust an interrupted current to stimulate the
muscle, either directly or indirectly.

{h.) Load the lever with 50 grams, and in doing so allow the
drum to move slowly. Remove the load and observe the curve
obtained.

{n.) Tetanise the muscle, and, while it is contracted to its greatest
extent, again load the lever with 50 grams while the drum is in
motion, and remove the load. Observe the curve.

{d.) Compare the two curves. The second curve will, of course,
begin higher, but notice that its absolute descent is greater than
the first curve, and that it does not rise to the horizontal again.

(e.) It is better to begin the experiment Avith the drum stationary,
and then to record the tracing with the drum in motion, or it may
be done with a stationary drum.

3. Blix's Myograph. — Although this myograph was described
many years ago, it seems to be but little used in this country.
Personally, I am indebted to Prof. Pick of Wtirzburg for his
kindness in showing it to me. By means of it one can readily
record the curve of extensibility of a passive or an active muscle.
The following summary is based on the description given by
Schenk.

Ill the mj'ogra{)h (fig. 140) the miiscle-clanii) and the part to which the
steel lever is attached form a rectangular piece, S S, which glide-s in a slot
formed by the guides, R R and R' R'. Tlie slider, S S, carries at a the axis of
the lever a b, and also a lateral piece. A, placed at right angles for tlie attach-
ment of the muscle, and one end of which is fixed to the lever at 6. The
weight is represented by P, which b}' means of the collar, r, presses on the
lever. Tliis collar, r, moves to and fro -not fiom side to side — between two
pairs of lixed studs, 1 1 and t^ t^.

2l8

PRACTICAL PHYSIOLOGY.

[XXXIX.

Suppose the slider to be pushed as far to the left that the axis, a, just lies
opposite to the collar, r — a i)oiut which is adjusted on the apparatus — then
the tension of the muscle is nil. On moving the slider with the hand towards
the right, so that the weight, P, acts on points of the lever more and more
removed from n, then the tension of the muscle increases steadily, when the
writing point, p, records the curve of extension, p, on a horizontally ])laced
and stationary wooden board or glass plate covered with smoked glazed ])aper.
In using the apparatus, board, slot, and slider are ])laced horizontally, the
weiglit, P, is not applied directly to/, but to the latter the weight is attached
indirectly by means of a cord which })asses over a pulley.

Apparatus. — Blix's myograph, induction coil arranged for repeated shocks,
the electrodes lieing directly connected with the muscle. The best prei)ara-
tion to use is the double semi-membranosus and gracilis (Lesson XXIX. 5)
placed side by side and firmly attached to the lever. For these muscles taken
from a large Jkma esculcnin. a weight of 2 kilos is used, and ibr the corre-
Sfioiiding gastrocnemius i kilo.

FlO. 140.— Scheme of Blix's Msosraph. S, S. .Slider; iJiJ and R R'. Guides for slider; a, 6.
Lever; A fDrniuscle ; P. Weiglit ; r. Collar; t t and ^i ti- Guides for collar carrying
weight ; p. Recording point. '

(a.) Take a curve of a passive muscle from the jioint of greatest tension to
nil tension.

{b.) Take a similar c\irve from a tetanised muscle. Compare the two
curves, and it will be found that the curve of extensibility of the j)assive
muscle is less steep than tliat of the tetanised muscle, i.e., a contracted
muscle is more extensible than a passive one.

(c.) On a tetanised muscle, move the slider so that the tension is increased
from nil to the greatest jjossiblc, i.e., the muscle is more and more "loaded,"
and then reverse this, so that from the greatest tension there is gradually
"unloading." The two curves so obtained do not coincide: the latter lies
considerably below the former. It would therefore aj)pear, as far as the con-
traction is concerned, that it is not a matter of indifference whether the
muscle is being gradually "loaded " or " unloaded."

4. Elasticity of an Artery. -
same wav.

-Test the elasticity of a strip of aorta in the

XL.]

TWO SUCCESSIVE SHOCKS.

219

LESSON XL.

TWO SUCCESSIVE SHOCKS-
METRONOME.

-TETANUS—

1. Two Successive Shocks. — The primai-y current may be
broken by means of a revolving drum, i.e., using the automatic key
(fig. 120). Two strikers can easily be arranged on the same
support (IS), and their angular deviation can easily be adjusted to
give any required interval between the two successive shocks.

Fig. 141 shows several tracings indicating the effect of summa-
tion or superposition of one contraction on another, and how the
result varies with the particular period or phase of the contraction
at which the second shock or stimulus is applied.

Fio. 141.— Effects of two Successive Shocks on a Muscle, i. Second stimulus applied
at X ; 2. Second stimulus applied at the second x ; 3. Second stimulus applied at X ;
4. Second stimulus applied at the second x .

Make four successive experiments, using break shocks.

(i.) Arrange the two closures for stimulation so that tbey are a
full muscle-curve apart. The second is usually slightly higher than
the first (fig. 141, i).

(ii.) Arrange on a different part of the cylinder, but on the same
abscissa, so that the second stimulus comes in on the relaxation of
the foregoing contraction. As the second contraction occurs before
the first one has ended, it starts from a higher level (fig. 141, 2).

(iii.) If the second stimulus is so arranged as to be thrown in on
the ascent of the first curve, and before the apex is reached, the

220

PRACTICAL PHYSIOLOGY.

[XL.

second ciirve is superposed on tlie first, and the heiglit of the com-
pound is greater than the original muscle-curve (fig. 141, 3).

(iv.) Apply the second stimulus within the latent period of the
first contraction. There is practically no alteration in the height
of the curve (fig. 141, 3).

2. Tetanus. — A tetanising current may be obtained by N"eef's
hammer, or by means of a vibrating rod. Apparatus. — Daniell's

Fia. 142.— Scheme of arrangement for Tetanus. VS. Vibrating spring ; M. Cup for
mercury. Otlier letters as before.

cell, five wires, flat spring, cup of mercury in a wooden stand,
induction coil, i)u Bois key, drum moving at the rate of 5 cm.
per second, — ^ e., the cylinder moves once round in ten seconds, —
crank -myograph.

(a.) Arrange the experiment as in fig. 142 ; the induction coil
for single shocks, short-circuiting the secondary circuit. Place in
the primary circuit the flat metallic spring, held in a clamp. One end
of the spring has a needle fixed at right angles to it, Avhich dips into
a cup of mercury. The needle hangs just above the mercury cup

Fio. 143.— Curves of incomplete and almost complete Tetanus.

when the spring is at rest, but dips in and out of the mercury when
it vibrates. The clamped end of the spring is connected with the
battery, while the mercury cup is connected with the induction
coil. Cover the mercury with alcohol and water (i : 3), to prevent
oxidation, and to keep the resistance more uniform. Select a
.strength of shock which gives response only at break, thus eliminat-
ing the make shock.

XL.]

TWO SUCCESSIVE SHOCKS — TETANUS.

221

(6.) Arrange a nerve-mnscle preparation as in fig. 1 1 9 to record
on a slow-moving drum. Let the writing-lever be a short one.

('•.) Fix the flat spring firmly in the clamp, with ten inches
projecting. Allow the drum to revolve, set the spring vibrating,
and while it is doing so, open the key in the secondary circuit, and
before the spring ceases to vibrate short-circuit the secondary
current.

(d.) Shorten the vibrating spring and repeat the experiment,
making the tracing follow the previous one.

(e.) Make several more tracings on the same abscissa, and let
them follow eacli other at regular intervals, always shortening the
springs until the tracing no longer shows any undulations, i.e.,
until it has passed from the phase of "incomplete" to "complete
tetanus,"

FlO. 144.— Tetanus Interrupter. IT. Wood block; VS. Vibrating spring; BS, Bff. Bind-
ing screws ; C. Movable clamp ; C. Clamp to fix spring ; Af. Cup of Mercury.

(/".) Take a tetanus-curve by introducing Neef's hammer (Helm-
holtz's side wire) instead of the vibrating flat spring.

{(J.) Study the tracings. The first tracings are indented, but
gradually there is more and more fusion of the teeth, until a curve
unbroken by depressions is obtained. In the curve of complete
tetanus the ascent is at first steep, then slightly more gradual,
speedily reaching a maximum, when the lever practically records a
horizontal line parallel to the abscissa. AVhen the current is shut
off the descent is very steep at first, and towards the end very
slow.

3. Number of shocks required to produce tetanus depends on the animal,
the muscle, and the condition ot the latter ; the more fatigued a muscle is, the
slower it contracts, and. therefore, the more readily does fusion of contractions
take place. A fresh Iron's gastrocnemius requires about 27-30 sliocks per

222

PRACTICAL PHYSIOLOGY.

[XL.

second to j)roduce complete tetanus. The following table shows approximately
the number of shocks per second required to produce tetanus.

Shocks per second.

Tortoise,

2 {Marey).

Frog (hyoglossusl,

10-15

,, (gastrocnemius),

27-30

Lobster (claw), .

20 (Richet).

„ (tail), .

40 {Richet).

Rabbit (red muscle),

4-10 XlXronecker

f and Stirling)

,, (white ,, ),

Bird, .

100 {Richet).

Insects, .

300-400 {Marey).

If the muscle be fatigued, then more or less complete fusion takes place
with a smaller number of shocks per second.

4. Take a tracing with 10 or 15 vibrations per second, and then test the
effect of different temperatures on the form of the tracing. Pour on the
muscle normal saline at the re(iuired temperature. Notice how cold helps
the fusion, while heat makes the tetanus less complete.

5. If Ewald's coil be used (fig. 95) any number of shocks from i to 200 per
second can be obtained.

ADDITIONAL EXERCISES.

6. Interruption by a Metronome. — Instead of the vibrating rod or NeePs

hammer, introduce into the primary
circuit a metronome (fig. 145), pro-
vided with a wire which dips into a
mercury cup introduced into the
primary circuit. Vary the rate of
vibration of the metronome, and ob-
serve the effect on the muscle-curve.

7. Instead of using the spring held
in a clamp, a convenient form is shown
in fig. 144. The spring is kept vibrat-
ing by an electro-magnet actuated by
two Grove cells.

8. Magnetic Interrupting Tuning-
Fork. — Instead of a vibrating spring,
the primary current may be inter-
rupted by means of a tuning-fork of
known rate of vibration, and kept in
motion by means of an electro-magnet.
The instrument (fig. 146) is introduced
into the primary circuit, and every
time the style on one of the arms of the
tuning-fork dips into and comes out

of the mercury placed in a small cup, the primary current is made and broken.

FiO. 145 —Metronome.

XLI.] FATIGUE OF MUSCLE. 223

One of the most important points in connection with the use of this instrument
is to keep the suilace of the mercury clean and bright. This is necessary in

Fig. 146— Jilngnetic Interrupter with Tuniiur-Fork. as made by the Cambridge Scientitic
Iiistiument Company.

order to have the successive shocks of equal intensity. Kronecker has devised
such an apparatus. The vibrating rod is so adjusted that stimuli from i to
50 or 60 per second can be obtained therewith.

LESSON XLI.
FATIGUE OF MUSCLE.

1. Fatigue of Excised Muscle.

(a.) Arrange an induction coil for break shocks, hut interrupt
the primary circuit automatically by means of the drum key (fig,
120).

{/).) Fix a nerve-muscle preparation on a crank-myograph, with
a long levor and a weight of 40-50 grams, lay the nerve over the
electrodes from tlie short-circuited secondary coil, and let the lever
record on the dnnn. A break shock is obtained each time the
drum revolves. The myograph should be supported on a tangent
stand. If a tangent support be used for the muscledever, then,
although the muscle contracts at eacli revolution of the cylinder,
one may record every tenth or fifteenth contraction just as one
pleases (fig. 147).

(c.) Observe that the heiglit of the curves falls, while their
duration is longer. In nearly every case fatigue-curves from muscle
show a "staircase" character (fig. 148), the second curve being
higher than the first one, and the third than the second.

2. Fatigxie -Curve of Excised Muscle. — (a.) Use a slow-revolving drum on
which to record the muscle tracings, so slow that the ascent and descent of
the lever form merely one line. Let the primary current be broken at regular
intervals by means of a revolving drum with a platinum style attached to its
spindle, to make and break the primary current at every revolution (fig. 148).
In this way a curve such as fig. 148 is obtained.

224

PRACTICAL PHYSIOLOGY.

[XLI.

(h ) Note the " staircase" character of the curve, i e., the second contraction
is hilhe? than the first, the third than the second, and so on tor a certain
number of contLtions. After that the height of the contraction falls

second.

Steadily so that a line uniting the apices of all the contractions forms a

^'t?i"lgi:'rvt^^^^^^ "lift" is recorded, note that the rise of

thekver increases with the number of stimuli-the strength of ,«- stimulus
remaining constant, so that one gets the i.henomenon of the Trepie or
- sta rcase " After a time it falls steadily until the excitability is ex-
tinau shed (fig 48). Note also that in the phase of relaxation the lever does
not'reach the°absci sa, i.e., relaxation takes place so slowly as if one had to

f 10. i48.-Fatigue-Cuive of an Excised Frog's Muscle recorded on a Slow-moving Drum,

deal with a so-called " contracture." II che march of events be arrested, and
t'me given for repose, then, on stimulating, tne lift increases, but the effect
lasts only for a short time.

XLIl.]

FATIGUE OF NERVE. 225

LESSOX XLIL
FATIGUE OF NERVE -SEAT OF EXHAUSTION.

1. Can Nerve be Fatigued?— "We liave seen tliat a muscle
manifests fatigue, i.e., its store of material and energy are gradually
used up, so that it shows a diminished capacity to respond to
stimulation. Does a nerve manifest such phenomena ? Reasoning
a priori, from the fact that the only known sign obtainable during
the activity of a nerve is the " negative variation of the nerve-
current," one is led to suppose that very probably nerve-fibres
partake but little if at all in the phenomena of fatigue. In fact, we
shall find that nerve is practically inexhaustible.

Suppose one stimulated a nerve of a nerve-muscle preparation
with maximal induction shocks until tlie muscle ceased to respond
to indirect stimulation. This would afford no proof that the muscle
itself was fatigued. Why ? Stimulate the muscle directly, and it will
respond. Therefore the seat of fatigue in this case is not primarily
in the muscle, but must be sought for either in the nerve itself or
at tlie end-plates where the nerve comes into relation with the
muscular substance.

2. Seat of Exhaustion — is it in Muscle, Nerve or End-Platea ?

A. Not i/riinariJii in Muscle.— {a.) Arrange an induction coil for repeated
shocks. Connect the secondary coil with a Pohl's commutator without cross-
bars.

[h. 1 Prepare a nerve-muscle preparation, with a straw flag, or use a crank-
myograph, and place its nerve over Du Bois electrodes attached to the com-
mutator. Pass two fine wires tlirough the gastrocnemius and attach them to
the other two binding screws of the commutator.

('•. ) Tetanise the nerve until the tetanus ceases. Then reverse the commu-
tator and stimulate the muscle. It contracts. Therefore, ^/ie sca< of fatigue
is not in the muscle.

B. Not in the Nerve {Nrve is prnctically inexhaustible). — [a.) Arrange a
nerve-muscle preparation in connection with a coil for repeated shocks as
before. Place the nerve over the electrodes from the secondary coil.

{b.) Arrange a DaiiieH'scell connected toN.P. electrodes, and short-circuited
for a constant current— the " polarising current " (Lesson XLVIII ) — and place
the N. P. electrodes next the muscle, so tiiat the - pole is next the muscle, i.e.,
with the j)olarising current descending. The " polarising current" so lowers
the excitability of the nerve as to "block" the jjassage of a nerve impulse
through this part of the nerve. Tlie tetanising electrodes are placed near the
upper cut end of the nerve.

(c. ) See that the muscle responds when the stimulating current acts on the
nerve, then tlirow in the polarising current, when at once the muscle ceases
to respond, because the nerve imjiulse is blocked. Go on stimulating the
nerve for an hour or longer. We know that if there had been no " block " the
muscle would long ere this have ceased to respond to indirect stimulation.

P

226 PRACTICAL PHYSIOLOGY. [XLIII.

(d.) Close the key ol the polarising circuit, i.e., remove the block. The
muscle responds at once. Therefore the loss of excitability or scat of exhaus-
tion is not in the Jierve {Bernstein). Where is it, then 1 It must lie primarily
somewhere between the nerve and muscle, i.e., it is in the end-plates, or where
nerve joins muscle. Moreover, Bowditch has shown that the sciatic nerve of
a curarised cat may be stimulated for hours, there being no muscular
response, but as soon as the effect of curare, which is known to paralyse the
nerve-terminals in striped muscle, passes off, the muscles of the foot respond.

C. The two results of B and C may be combined thus : —

(a.) Dissect out two nerve-muscle preparations (A and B) from a frog,
clamp both femurs in one clamp, and attach straw flags of different colours
to both legs (fig. 114). Lay both nerves over a pair of Du Bois electrodes.
Cover them, keep them moist.

{b. ) Attach the electrode wires to two of the binding screws of the commu-
tator without cross-bars", turning the handle, so that the current can be passed
through both nerves when desired.

(0.) To the nerve of B, between the Du Bois electrodes and the muscle,
apply a "polarising current" with its - pole next the muscle.

{d. ) Pass an interrupted current through both nerves ; A will become tetanic
while B remains quiescent ; the impulse cannot pass because of the " block"
produced by the "jjolarising current."

(e. ) Continue to stimulate the nerves until A ceases to respond. Break
the polarising current, i.e., remove the block on B ; B becomes tetanic.

As both nerves have been equally stimulated, both are equally fatigued or
non-fatigued. As B becomes tetanic, the seat of the fatigue is not in the
nerve- trunk.

As in A the seat of fatigue was not in the muscle, and as B shows that
nerve-fibres practically do not manifest the signs of fatigue, it would seem
that its seat must be somewhere between muscle and nerve, in all probability
in the end -plates.

LESSOI^ XLIII.

MUSCLE WAVE— MUSCLE THICKENING— WILD'S
APPARATUS.

1. This is best done by the method originally used by v. Bezold,
and modified in a simple form by Biedermann. A muscle with
parallel fibres — preferably a sartorius— is fixed a little to one side of
the middle line in a cork clamp so tliat the direct transference of
the change of muscle form, but not the excitation process in the
muscle, is prevented from passing, ?>., one part of the muscle is
stimulated while the other part records.

(a.) Arrange an induction machine in connection with a com-
mutator witliout cross-bars and two paii.i of thin wires, so as to be
able to send a single maximum break shock through either pair of
wires as in the curare experiment (Lesson XXXIII.). Let the
primary current be broken by the automatic drum key. Arrange

XLIII.] MUSCLE WAVE. 227

a recording crank-myograph. Arrange time marking apparatus

(ttttt )•

{h.) Dissect off with great care the sartorius of a ciirariaed frog
(p. 1 86), and connect its tibial end with the myograph-lever.

(c.) Clamp the muscle a little to the tibial side of the middle
line in a cork clamp, made by pushing two pins parallel to each
other through two tliin pieces of cork ; the i)oints of tlie pins project
and serve to fix the preparation on the cork plate of the myograph
(fig. 149).

{(I.) Thrust two pins through the muscle close to the clamp
and two near its free end. These act as electrodes and are con-
nected with the thin wires from the commutator, so that the muscle
can be stimulated either near the clamp or far away from it.
Stimulate the muscle first near the clamp and record the contraction,
reverse the commutator, excite it away from the clamp and record.
Two curves, one rising later than the other. The distance between
the two indicates the time taken by the wave of contraction to pass

Fig. 149. — Arrangement for study of Muscle Wave. E, E'. Pin electrodes ; C. Cork
clamp ; L. Lever.

over the distance from the far to the near electrodes. Measure the
distance between the electrodes and calculate its velocity. It varies
from I to 2 metres per second.

(e.) Test the effect of cold normal saline in slowing its rate.

2. (a.) Arrange two long straw levers on a cork frog-plate so
that the two free ends of the levers record exactly over each other
on a revolving drum. Record time (y^").

(/'.) Remove the double semi-membranosus and gracilis (p. 179) of
the thigh from a curarUnI frog, together with their bony attachments,
and place them under the levers, the lovers lying across them, and
as far apart as possil)le. Let the muscles rest on paraffined paper.
Fix the muscles tlirough their bony attachments by means of pins.
Through one end of the muscles push two pins attached to wires to
act as electrodes. Some prefer the two sartorii muscles, fastened
together, the one lying on the other and fixed by means of pins.

(c.) Stimulate with a maximal break induction shock and note
that two curves ou different abscissae are obtained, the one a little

228

PRACTICAL PHYSIOLOGY.

[XLIIL

later than the other. The distance between the two indicates tlie
time taken by the contraction to pass from the one lever to the
other. Test the effect of cold normal saline.

Fio. 150. — Marey s Registering Tambour. Metallic capsule, T, covered with thin india-
rubber, and bearing an aluminium disc, wliich acts on the writing-lever, U.

3. Thickening of a Muscle during Contraction.

(re.) Arrange a Marey's tambour to write on a penduhim-myograph (fig.

150)-
(6.) Fix Marey's pincc myoqraphique (fig. 151) so as to compress the
adductor muscles between the thumb and the
metacarpal bone of the index-finger, keeping the
two arms together with an elastic band. Or use
a pair of toy bellows, to the arms of which ]>late-
like electrodes are fitted and connected with bind-
ing screws. Keep the handles of the bellows
pressed upon the adductor muscles by means of
an elastic band. Connect the receiving tambour
of the pince or the nozzle of the bellows with
the recording tambour, introducing a valve or
T-tube with a screw clamp into the connecting
elastic tube, to regulate tlie pressure of air within
the system of tubes.

('•. ) Arrange an induction machine with the
trigger-key of the penduhim-myograph in the
jirimary circuit, and the ])ince or bellows in the
secondarj'. Take a tracing. The time relations of the conti'action are de-
termined in the manner already stated (Lesson XXXVIL).

Fig. 151. — Marey's Pince Myo-
graphique, as made by
Verdin.

4. Wild's Apparatus consists of a glass cylinder made by inverting the
neck-end of a two-ounce phial. The neck is fitted with a cork, the ujjper end
is 0}>en (fig. 152, B). A wire connected with a key (K') siiort-circuiting the
secondary coil ot an induction machine ])erlorates the cork. Arranged above
is a light lever (L) provided with an after-load («/), and moving on an axis, the
short arm projecting over the mouth of the jar. Tiie whole arrangement is
fixed to a jjlatform i P), with an adju.stable stand (S) bearing the fulcrum of the
lever and the after-load. The cork must be renewed witii each new drug used.

(a.) Dissect out the gastrocnemius, divide the femur with the gastrocnemius

XLIV.]

MYOGRAPHIC EXPERIMENTS ON MAN.

229

attached just above the attacliment of the latter, and the tibia below the knee-
joint. Pass a fine metallic hook through the knee-joitit or its ligaments, and
attach it to the projecting hook of fine wire fixed to the short arm of the lever.
Fix the tendo Achillis to a hook connected with the wire passing through the
cork in the neck of the glass cylinder.

Fig. 152— WiWs Apparatus for Studyin;,' the Action of Poisons on Muscle. D. Drum ;
P. Platform ; S. Stand ; al. After-load ; L. Lever; B. Bottle with muscle ; K' . Key.

{It.) Fill the glass cylinder — which encloses the muscle — not quite full with
normal saline. Stimulate the muscle directly with a break shock, using a
mercury key in the primary circuit, and take a tracing.

[r.) Remove the noi-mal saline with a pipette, and replace it with a solution
of the drug whose action you wish to study, e.g., veratria 1 in 5000, or barium
chloride i in 1000. Study the veratria tracing (fig. 137).

5. Interference Phenomenon in Nerve-Muscle Preparation. — Arrange a
nerve-muscle preparation in a moist chamber, and weight the recording lever
with 20 grams. Place the central end of the nerve over platinum electrodes,
and allow a portion of the nerve nearer the muscle to hang in the form of
a loop in contact with strong glycerin, when the muscle becomes tetanic.
When tetanus occurs throw in an interrupted current, when the tetanus is
diminished. Is this interference-phenomenon an inhibitory one ? ^Kaiser,
Zeitsch. f. Biol., 1891, p. 417.)

LESSON XLIV.

MYOGRAPHIC EXPERIMENTS ON MAN-
ERGOGRAPH AND DYNAMOGRAPH.

1. Myographic Experiments on Man.

Pick has devised a simple apparatus for this purpose, using
isometric curves. The muscle investigated is the Abdurtor indicis
or inteivstfeus dovKalis primus of the hand. It arises by two heads
from the adjacent surfaces of the metacarpal bones of the thumb and
index-finger, and is inserted into the dorsal aponeurosis of the latter.

230

PRACTICAL PHYSIOLOGY.

[XLIV.

Apparatus. — In a prismatic piece of wood, H, firmly fixed to a base, a hole
is cut down to the level, K, through which one can conveniently place one's
hand (fig. 153) ; tlie ulnar surface of the hand rests on the rounded lower end

of the hole, while the thumb rests
against the lateral wall of the hole,
so that in this way the hand is
sufficiently fixed. Over the index-
finger is placed a collar made of
strong iron wire, and through this
collar ])roject the three other
fingers, which hang free, the collar
itself lying over the joint between
the second and third phalanges.
To the collar is attached a strip ot
iron with a notch in it, by means of
which it is attached to the axis of
the lever, which is one so arranged
as to give isometric contractions as

in fig- 153-

When one attempts to raise the
index-finger, the muscle records an
isometric curve. As the collar can
at most move only i mm., and as
the muscle itself acts on a lever
about five times shorter than the
distance of the point of attachment
of the collar from the axis of rota-
Seen from the tion of the index-finger, the muscle
can at most contract i mm. The
muscle records on a revolving
(From the description of Schenk. See Fick, Ffiiiyer^s ArcJiiv, Bd.

Fia. 153. — Pick's Apparatus for Studying Ten-
sion of Abductor Indicis. //. Wooden
rod with hole, K, for hand ; D. Iron-wire
collar, acting through JS on an axle, N, to
which a lever is attached
end.

surface.
41, p. 176.)

With this apparatus one can study (i) The force of contraction ; (2) The
effect of fatigue and recovery ; (3) One may excite the muscle by means of
electricity ; (4) One may compare the mechanical resj)onse elicited by electrical
(tetanic) and the normal physiological stimulus, and learn that during a
voluntary contraction there is a greater contraction, i.e., a greater liberation
of energy than during the strongest contraction elicited by electrical stimu-
lation.

2. Mosso's Ergograph for Fatigue and Work. — Tliis is a most useful
instrument (fig. 154), by means of which the student can study the process of
fatigue on himself, the conditions that predispose to it, and the process ot
recovery, as well as the effect of vari jus conditions on the fatigue-curve. By
means of this instrument also the amount of work done is recorded graphic-
ally, and can be estimated in terms of kilogrammetres, the contractions in
this case being isotonic. The forearm is fixed by means of clamps upon an
iron framework, while the hand also is firmly fixed, the index and ring
fingers being placed in brass hollow cylinders, while the middle finger is free.
The forearm is placed in a half-supinated position. To the middle finger is
attached a cord, passing to the writing-style, and to the latter is attached a
weight, which can be varied. The style writes upon a recording drum
moving horizontally. The forearm is fixed in the apparatus, and the middle
finger attached to the writing ap])aratus, and to the latter is added a load of
known weight, cf., 2-3 kilos. The experimenter flexes the middle finger,
lifts the load, and as soon as the contraction is over the load extends the

XLV.]

ELECTRO-MOTIVE PHENOMENA.

231

finger. The experimenter contracts the muscles, moving his middle finger
at a given rate, say once every two seconds, either by listening to the beat of
a metronome, or observing the motion of a pendulum vibrating a definite
number of times per minut-. (A. Mosso, "Fatigue of human muscle," Du
Bo'is-Reymnnd's Archiv, 1890, and Die Enniidung, Leipzig, 1892 ; Warren
P. Lombard, '"Some of the influences which affect the power of voluntary
muscular contraction," ./wa?vw^ o/'iVt(/Aio/o^(/, xiii. i.)

3. Dynamograph. — "Waller has devised a simple form of this.
To the vertical arm of a dynamometer of Salter (p. 1S9). a strong
,-teel spring with a long recording arm is attached, the record
being made on a very slow-moving drum, e.g., a cylinder placed
vertically on the hour-spindle of an American clock. The
dynamograph is so arranged that it can be clamped to a table. The observer,
by grasping the handles of the instrument, makes a series of maximal efforts,
say 30 per minute, —i.e. , each lasting two seconds, — then he takes one minute's
rest, and re])eats the experiment.

\n this way one can measure the muscular strength and how it declines
with each contraction or series of contractions, together with its recovery
during rest. We have a series of isometric contractions.

LESSON XLV.

DIFFERENTIAL ASTATIC GALVANOMETER— NON-
POLARISABLE ELECTRODES-SHUNT-DEMAR-
CATTON AND ACTION-CURRENTS IN MUSCLE.

ELECTR(J-,^IOTIVE PHENOMENA OF MUSCLE
AND NERVE.

1. Thomson's High-Resistance Diiferential Astatic Galvano-
meter.

{a.) l*lace the galvanometer (tig. 155) upon a stand uuaflected

PRACTICAL PHYSIOLOGY.

[XLV.

bv vibrations, e.g., on a slate slab fixed into the wall, or on a solid
stone pillar fixed in the eartli, taking care that no iron is near.

(Jb.) Let the galvanometer face tre-''t, i.e., with the plane of the
coils in the magnetic meridian, the magnetic meridian being ascer-
tained by means of a magnetic needle. As the galvanometer is a
differential one, to convert it into a single one, connect the two

Fig. 156.— Lamp and Scale for Ihontt-
son's Galvanometer

FI6. 155.— Sir William Thomson'^ Re-
flecting Galvanometer, u. I'pper,
/. Ixiwer coil: *, t. Levelling screws ;
»/». Magnet on a bra&s support, b.

FI6. 157. — Ifon-
Polarisable Elec-
trodes. Z. Zincs ;
E. Cork ; a. Zinc
sulphate solu-
tion : (, t Oay
points.

central binding screws on the ebonite base by means of a copper

wire.

(r.) By means of the three screws level the galvanometer.

('/.) Take off the glass cover and steadily raise the small milled
head on the top of tlie upjier coils, which frees the mirror, and
allows it to swing free. Replace the glass shade.

(e.) Place the scale (fig. 156) also in the magnetic meridian and

XLV.] ELECTRO-MOTIVE PHENOMENA. 233

I metre from the mirror, taking care that it is at the propar height.
Instead of a sUt in tlie scale, it is better to fix in it a thin wire, and
by means of a lens of short focal distance to bring the image of the
wire to a focus in the middle of the illuminated disc of light
reflected from the mirror upon the scale.

(/'.) Light the paraffin lamp, place the edge of the flame towards
the slit, darken the room, and see that the centre of the scale, its
zero, the slit in the scale, the flame of the lamp, and the centre of
the mirror, are all in the same vertical plane, so that a good liglit
is thrown on tlie mirror in order to obtain a good image on the
scale.

(g.) Make the needle all but astatic by means of the magnet
attached to the bar above the instrument. The needle is mod
sensitive tvJien it swings slowly.

(h.) Test the sensitiveness of the galvanometer by applying the
tips of two moist fingers to the two outer binding screws of the
instrument, when at once the beam of light passes olf the scale.

2, Non-Pol arisable Electrodes. — One may use the old form
of Du Bois-Reyraond, the simple tube electrodes, or the "brush
electrodes " of V. Fleischl (fig. 160).

(A.) (a.) Use glass tubes about 3 cm. long and 5 mm. in diameter,
tapering somewhat near one end, and see that they are perfectly
clean.

(h.) Plug the tapered end of the glass tube with a plug of china
clay, made by mixing kaolin into a paste with normal saline.
Push the clay into the lower third or thereby of the tube ; plug
the latter, using a fresh-cut piece of Avood or thin glass rod to do
so ; allow part of the clay to project beyond the tapered end of the

tube(fig._i57, ^, /).

(c.) "With a clean pipette half fill the remainder of the tube with
a saturated neutral solution of zinc sulphate. Make iivo such
electrodes.

{d.) Into each tube introduce a well-amalgamated piece of zinc
wire with a thin copper wire soldered to its upper end (Z, Z), fix
the electrodes in suitable holders in a moist chamber, and attach
the wires of the zincs to the binding screws on the stage of the
moist chamber. The zinc should not touch the clay.

(B.) Some prefer a U-''5lifipPfl glass tube held in a suitable
holder attached to a vulcanite rod in the moist chamber
(B. Sanderson's pattern). The tube contains a saturated solution of
zinc sulphate as before. Into one limb of the tube is placed the
rod of amalgamated zinc. In the other free limb is placed a
straight tube with a slight flange at its upper end filled witli kaolin
moistened with normal saline, the kaoUn projecting as a cap above

234

PRACTICAL PHYSIOLOGY.

[XLV.

the level of the U -shaped tube. The muscle is placed on the
two corresponding kaohn caps.

3. Shunt. — This is an arrangement by which a greater or less
proportion of a current can be sent through the galvanometer (fig.
158). The brass bars on the upper surface
are marked with the numbers ^, -^^, gy-^,
indicating the ratio between their resistance
and that of the galvanometer, so that when
the plug is inserted in the several positions,
tVj tW' ^^ ToW ^f ^^^^ whole current may be
sent through the galvanometer.

4. Muscle Demarcation-Current (Current
of Injury).

{a.) Arrange the apparatus according to the
scheme (fig. 159).

{/>.) Place a shunt between the N.P. elec-

FiG. 1 58.- The Shunt. trodes and the galvanometer. Connect two

wires from the electrodes to the binding

screws (A, B) of the shunt, and from the same binding screws

attach two wires to the galvanometer. Insert a plug (C) between

Fig. 159.— Arrangement of Apparatus for the Demarcation-Current of Muscle. M. Muscle
on a glass plate, P ; S. Shunt ; G. Ualvanometer ; Mg. Its magnet moved by the
milled head, m ; L. and Se. Lamp and scale.

A and B, thus short-circuiting the muscle-current. When work-
ing with muscle, keep a plug in the hole opposite ^ on the
shunt. Arrange the lamp and scale so as to have a good image of

XLV.] ELECTRO-MOTIVE PHENOMENA. 235

the mirror on the zero of the scale ; adjusting, if necessary, by
means of the magnet moved by the milled head on the top of the
glass shade (fig. 159, ?»).

(c.) Test the electrodes, either by bringing them together or by
joining them with a piece of silk thread covered with china-clay
paste. After removing ail the pings from the shunt, there ought to
be no deflection of the spot of light. If there is none, there is no
polarity, and the electrodes are perfect.

(ff.) Ascertain the Direction of Current in Galvanometer. —
!Make a small Smee's battery with a two-ounce bottle. Place in the
bottle dilute sulphuric acid (i : 20) and two wires of zinc ( - ) and
copper ( + ), with wires soldered to them. Connect them with
the galvanometer. Arrange the shunt so that ^^ or yoVtt P^^^
of the current thus generated goes through the galvanometer.
Note the deflection and its direction. Arrange the N.P. electrodes
in the same way, and observe which is the negative and which
the positive pole corresponding to the zinc and copper of the
battery.

(e.) Prepare a Muscle. — Dissect out either the sartorius or
semi-membranosus of a frog, which consist of parallel fibres, but
avoid touching the muscle with the acid skin of the frog. Lay
the muscle on a glass plate or block of paraffin under the moist
chamber.

(/.) Keep one plug in the shunt at C, to short-circuit the elec-
trodes, and the other plug at ~. Cut a fresh transverse section at
one end of the muscle, and adjust the point of one electrode exactly
over the centre (equator) of the longitudinal surface of the muscle.
Apply the other electrode exactly to the centre of the freshly
divided transverse surface (fig. 159).

{(J.) Current of Injury.— Remove the short-circuiting plug, C,
from the shunt, keep one plug in at i, so that ^ of the total
current from the muscle goes through the galvanometer. Note the
direction and extent of the deflection. By noting the direction, and
from tlie observation already made (d), one knows that the longi-
tudinal sm'face of the muscle is -f- , and the transverse section - .
Replace the plug-key (C), and allow the needle to come to rest at
zero. The deflection was caused by the current of injury, and it
flows from the equator or middle of the muscle towards the cut
ends. It is also called tlie demarcation-current. The injured part
of a muscle is negative to the uninjured part, and the current in the
galvanometer is from the longitudinal ( -i- ) surface to the injured
negative transverse surface.

(A.) Bring the N.P. electrode on the longitudinal surface nearer
to the end of the muscle, and note the duninution of the deflection
of the needle. Replace plug C.

236

PRACTICAL PHYSIOLOGY.

[xlv

(/) Vary the position of the
electrodes and note the variation
in the deflection. If they be equi-
distant from the equator, there
is no deflection. The greatest
deflection takes place when one
electrode is over the equator and
the other over the centre of the
transverse section of a muscle
composed of parallel fibres. The
deflection, i.e., the electro-motive
force, diminishes as the electrodes
are moved from the equator or the
centre of the transverse section.
In certain positions no deflection
is obtained.

5. Negative Variation of the

Muscle-Current.

(rt.) Use the same

muscle preparation,
or isolate the gas-
trocnemius with
the sciatic nerve
attached. Divide
the muscle trans-
versely, and lay the
artificial transverse
section on one elec-
trode, and the longi-
tudinal surface on
„ . the other. Ob-
' Eiectro;^r/"o' serve the extent of
v. Fieischi. ^j^g deflection.
{},.) Adjust an induction coil
for repeated shocks, placing it at
some distance from the galvano-
meter.

(<•.) Take the demarcation-
current, observing the deflection,
and allow the spot of light to
take up its new position on
the scale. Tetanise the muscle
through its nerve, and observe
that the spot of light travels

XL VI.]

JJERVE-CtTRRENTS. ^37

towards zero. This is the "negative variation of the muscle-
current." If the gastrocnemius be ii.sed, stimulate the sciatic nerve.
Care must be taken that the muscle does not shift its position on the
electrodes. According to Hermann's theory, it is brought about as
folloAvs : — An injured part of a muscle (or nerve) is negative to an
luiinjured part — - ' negativity of injury," and similarly an active
part of a muscle is negative to an inactive part— " negativity of
activity." The demarcation-current or injury-current passing in
the galvanometer from the longitudinal + to the transverse - surface
is diminished, because, when the muscle contracts, there is a current
set up — action-current — in the opposite direction, which diminishes
the total current acting on the galvanometer.

ADDITIONAL EXERCISES.

6. Brush Electrodes of V. Fleischl (tig. i6o) consist of glass tubes 5 mm.
ill diameter and 4 cm. long. Into one end is fitted a perfectly clean camel's-
hair pencil, and into the other dips a well-amalgamated rod of zinc with a
binding screw at its free end. Place some clay in the lower part of the tube,
and then fill it with a saturated solution of zinc sulphate. A piece of india-
rubber tubing fits as a cap over the upper end of the glass tube. The brushes
are moistened with a mixture of kaolin and normal saline.

7. D'Arsonval's Non-Polarisable Electrodes (fig. 161). — The electrodes
consist of a silver wire coated with fused silver chloride. The silver wire is
held in a suitable stand, while the silver chloride coated i)art is placed in a
tube tapering to a point below and filled with normal saline. At the lower
tapered end there is a small a})erture into which is introduced a thick thread.
The tube is closed above with a cork (C), through which passes the silvei
electrode (A). The tapered points are brought into contact with the tissues.
They should be kept in the dark.

Vertical Electrodes of Fick. — Into a vertical glass tube the amalgamated
zinc is introduced from below, the tube is filled with a saturated solution of
ZnS04, but the nerve rests on a hammer-shaped piece of baken porcelain,
such as is used for porous cells for batteries. It is soaked with salt solution,
and has a process which dips into the zinc sulphate. Several of these can be
arranged side by side in a suitable holder.

LESSON XLVL

NERVE - CURRENTS — ELECTRO - MOTIVE PHENO-
MENA OF THE HEART— CAPILLARY ELECTRO-
METER.

1. Demarcation-Current of Nerve.

(a.) Render the galvanometer as sensitive as possible by adjusting at a suit-
able height the north pole of the magnet over the north pole of the upper
needle.

238

PRACTICAL PHYSIOLOGY.

[XLVL

{b.) Prepare N.P. electrodes for a nerve. In this case the electrodes are
hook-shaped, and one is adjusted over tlie other. The upper hooked electrode
has a groove on its concavity communicating with the interior of the tube
(fig. Ib2). Place only one ])lug in the shunt between A and B.

(c. ) Dissect out a long stretch of the sciatic nerve, make a fresh transverse
section at both ends, hang it over the up])er N.P. electrode (N), and resting
with its two cut ends on the lower electrode (C), thus doubling the strength
of the current (fig. 162).

{d.) Remove t'ne plug h'om C in the shunt and pass the whole of the de-
marcation nerve-current through the galvanometer, noting the deflection.

(e.) Instead of adjusting tlie nerve as in (c. ), it may
be so placed on the ordinary tube N.P. electrodes that
the cut end rests on one electrode and the; longitudinal
surface on the other, thus leaving part of the nerve free.
Observe the deflection in this way.

2. Action-Current of Nerve.
[a.) Observe the amount of deflection as in (1. «.).

Stimulate with an interrupted current the free end of
the nerve, and observe that the sj>ot of light travels
towards zero. This was formerly called the " negative
variation " of the nerve-current.

3. Electro-Motive Phenomena of the Heart. — The

arrangement of the apparatus is the same as in Lesson
XLV.

(a.) Make a Stannius prejiaration of the heart, using
only the first ligature (Lesson LV. 1) to arrest the
heart's action. Lead oflf with brush N.P. electrodes
fi-om base and apex of the quiescent uninjured heart ;
there is no deflection.

{b.) Pinch tlie apex so as to injure it; it becomes
negative ; a diflereiice of potential is at once set up and
now the spot of light oscillates with each beat of the heart.

(c.) Excise a heart so as to get a spontaneously beating ventricle : lead ofl
fi'om the base and a]»ex of the latter ; observe the so-called " negative varia-
tion " with each contraction.

(d.) See also Lesson XLVII. 6 for secondary contraction excited by the
beating heart.

Fig. 162.— Nerve N.P.
Electrodes. N. Nerve ;
C. Clay of electrodes ;
Zn. Zincs.

4. Capillary Electrometer.

(a.) Lead off" a muscle to the two binding screws of a capillary electrometer.
The fine thread of mercury must be observed with a microscope.

By means of the capillary electrometer Waller has shown the diphasic
variation of the heart-current in man and in a living dog.

XLVII.]

GALVANIS EXPERIMENT.

239

LESSON XLVII.

GALVANI'S EXPERIMENT— SECONDARY CONTRAC-
TION AND TETANUS — PARADOXICAL CON-
TRACTION—KtJHNE'S EXPERIMENTS.

1. Galvani's Experiment.

(a.) Destroy the brain of a frog, divide the spine about the
middle of the dorsal region, cut away the upper part of the body,
and remove the viscera. Remove the skin from the hind-legs, divide
the iliac bones and urostyle, avoid injuring the lumbar plexus,
which will remain as the only tissue con-
necting the lower end of the vertebral
column with the legs. Thrust an S-shaped
copper hook througli the lower end of the
spine and spinal cord (tig. 163).

(b.) Hook the frog to an iron tripod.
Tilt the tripod so that the legs come in
contact with one of the legs of the tripod ;
vigorous contractions occur whenever the
frog's legs touch the tripod.

(c.) With the frog hanging perpendicu-
larly without touching the tripod, make a
U-shaped piece of wire composed of a
copper and zinc wire soldered together.
Touch the nerves above with the copper
(or zinc) end, and the muscles below with
the zinc (or copper), when contraction occurs at make, or break,
or both.

Fig. 163.— Galvani's
Experiment.

2. Contraction without Metals.

(a.) Make a fresh nerve-muscle preparation, leaving the leg
attached to the femur, and having the sciatic nerve as long as possible.
Hold the femur in one hand, lift the nerve on a camel's-hair pencil or
glass rod moistened with normal saline, and allow it to fall upon the
gastrocnemius, when the muscle will contract. Contraction occurs
because the nerve is suddenly stimulated, owing to the surface of
the muscle having different potentials.

(A.) Or remove the skin from the hind legs of a frog, and dissect
out the sciatic nerve in its whole extent. Divide it at its upper
end. If the nerve be lifted on a glass rod and allowed to fall
longitudinally on the triceps muscle there is no contraction.

240 PRACTICAL PHYSIOLOGY. [XLVIl.

Make a transverse cut across the triceps, and so arrange the
nerve that its cut end rests on the transverse section of the
muscle, and its longitudinal surface on the longitudinal surface of
the muscle. As soon as this interval is bridged over, the leg muscles
contract.

There is a large difference in potential between the transversely
cut muscle and its longitudinal surface — there is a " muscle-current "
in the muscle from tlie artificial transverse section to the longitudinal
surface, so when the nerve bridges over these surfaces, there is an
external derivation-current passing in the nerve, whereby the latter
is stimulated.

Thus the " physiological ^heoscope " is used to show the
presence of electrical currents in muscle under certain conditions.

3. Secondary Contraction or Twitch and Secondary Tetanus.

(a.) Arrange an induction coil for single make and break shocks.
Make two nerve-muscle preparations.

(b.) Place the left sciatic nerve (A) over the right gastrocnemius
(B) or thigh muscles, and the right sciatic nerve over the electrodes
(E) (fig. 164).

('•.) Stimulate the nerve of B with single induction shocks — the
muscles of both. B and A contract. The contraction in A is called

a secondary contraction. A is the
rheoscopic limb as by its contraction it
sliows the existence of an electrical
current in B. When B contracts,
there is a sudden diminution of its
muscle-current, which circulates in the
nerve of A. This sudden diminution
— negative variation — is tantamount
to a stimulus, and so the nerve of A
is stimulated.

((/.) Arrange the induction coil for
repeated shocks, and stimulate the
nerve of B. B is tetanised, and so is
A simultaneously. This is secondary
eio. i64.-secoiKiary Contraction, tctanus. The nerve of A is stimulated
by the sudden series of negative varia-
tions of the muscle-current during the contraction of B. So that
the electrical change during tetanus is interrupted and not con-
tinuous like the change in form of the muscle, and with 50 shocks
per second each electrica- chang? must reach its maximum and
subside in y^".

(e.) Ligature the nerve of Aiiear the muscle, stimulate the nerve
of B : there is no contraction of A although B contracts.

XLVII.}

SECONDARY CONTRACTION.

241

(/. ) Prepare another limb and adjust it in place of A, ligature the nerve of
B. On stimulating the nerve of 15, no contraction takes place either in A or
B.

4. Secondary Contraction from Nerve.

(a.) Make a nerve-muscle preparation and place it on a glass
plate (B). Dissect out the s(;iatic nerve of the opposite side (A).
Lay I cm. of the isolated sciatic nerve (A) on a similar length of
the nerve of the nerve-muscle preparatioji (B) (tig. 165)

(/'.) Stimulate A with a single induction shock ; the muscle of
B contracts. Stimulate A with an interrupted current ; the muscle
of B is thrown into tetanus.

('■.) Ligature A and stimulate again. B does not contract.
Therefore its contraction was not due to an escape of the stimulating
current. The " secondary contractions " in B are due to the sudden
vari.itions of the electro-motivity produced in A when it is stimu-
lated.

'^''^^>-.

^^nm —

Fig. 165.— Sclienie of .Secondary
C.mttiirtiiiii.

FlO. 166. — Scheme of Paradoxical
Contraction.

5. Paradoxical Contraction.

('^) Ari'angement. — Arrange a Daniell's cell and key for giving
a galvanic current, or use repeated induction shocks.

(/'.) Pith a frog, expose the sciatic nerve down to the knee (tig.
166, S). Trace the two hranches into which it divides. Divide
the outer or peroneal hranch as near as possible to the knee, and
stimulate its central end (P) by a faradic current. A certain
strength of current will be found whereby the muscles supplied by
the other division of the nerve are thrown into tetanus (T). The
tibial nerve to the gastrocnemius is stimulated by escape or spread
of " electrotonic " currents from the excited nerve.

242 PRACTICAL PHYSIOLOGY. [XLVIL

(c.) Instead of inductiou shocks, use a shook from a Daniell's
cell. There is a paradoxical twitch.

No paradoxical response is produced by stimulation other than
electrical stimuli, e.g., section of a nerve, salt. It is still produced
even if the peroneal nerve be ligatured on the central side of the
seat of stimulation.

6. Frog's Heart-Current (Secondary contraction).

(a.) Injured Heart. — A quiescent uninjured heart gives no
current, but an active heart does, and so does an injured one. The
action-current of an injured heart is easiiy shown when a nerve of
a nerve-muscle preparation is placed on a beating rabbit's heart
inside the thorax. In the frog, it requires some care to show this.
It is easy, however, to obtain a secondary contraction from a
beating injured frog's heart.

Prepare a nerve-muscle preparation or rheoscopic limb. Excise
the heart of a pithed frog, and place it on a dry glass plate, removing
the surplus blood. Cut off tlie apex of heart, and to it apply the
transverse section of the divided sciatic nerve, letting a part of
the longitudinal surface of the nerve rest on the uninjured ventricle.
"With each beat of the heart there is a twitch of the rheoscopic
limb or muscle.

(h.) Action-Current of Uninjured Frog's Heart. — On placing the
nerve of a nerve-muscle preparation along the exposed frog's heart
from apex to base, one sometimes gets a muscular response to each
beat of the heart, but the experiment does not always succeed.
It is easier to do it on a Stanniused heart ; with each contraction
of the heart excited artificially, there is a secondary contraction.

ADDITIONAL EXERCISES.

7. Kiihne's Nerve-Current Experiment.

(re.) Invert an earthenware bowl (B), and with wax fix to its base a piece of
glass lo cm. square (fig. 167, G).

(h.) Make two rolls of kaolin (moistened with normal saline), about i cm.
in diameter and 6 cm. in length (P, P'), bend them at a right angle, and
hang them over the glass plate about 6 mm. ai)art.

('■. ) Make a norve-muscle preparation, lay the muscle on the glass plate,
and the nerve (N) over the rolls of china clay.

{d.) Fill a small glass vessel (Cj with normal saline, and allow the two
free ends of tiie clay to dij) into it. With each dip the muscle contracts. In
this case the nerve is stimulated by the comj>Ietion of the ciicuit of its own
demarcation-current, and this in turn indirectly stimulates tlie muscle.

8. Kiihne's Muscle-Press — Secondary Contraction from Muscle to Muscle.
— Prei)are tvo sartorius muscles of a frog. Place the end ot one muscle

xi,viir.]

ELECTROTONUS.

243

over the end of the other, both muscles being in line with each other, and
the overlajiping portion so arranged that they can be ])ressed together by
means of the small sciew-jjress devised by Kiiline for this jiurpose.

On stimulating — by electrical, chemical, or other stimuli — the ft'ee end of
either muscle, so as to
cause that muscle to con-
tract, the second muscle
also contracts. The nega-
tive variation of the
muscle-current stimulates
the second muscle. This
result does not take place
if a thin layer of tinfoil
be placed between the two
muscles.

9. Biedermann's Modi-
fication of Secondary
Muscular Contraction. —

If a frog be denuded of its
skin and left exposed to
the air for twenty-four

Fig. 167.— Kiihne's Experiment. B. Bowl ; G. Glass plate
iV^. Nerve ou P, P' , Pads of claj' ; C. Capsule.

hours — the time varying with the temperature, amount of moisture in the air,
&c. — on causing one muscle to contract, other muscles contract secondarily.
On placing the two sartorius muscles in direct contact with each other, when
one mu.scle is made to contract, the other does so secondarily without the use
of a muscle-press.

LESSOX XLYIir.

ELECTROTONUS— ELECTROTONIC VARIATION
OF THE EXCITABILITY.

Electrotonus. — When a nerve is traversed by a constant
current, its .so-called "vital" properties are altered, i.e., its excita-
bility, conductivity, and electromotivity. The region of tlic
nerve atl'ected by tlie i)0sitive pole i.s said to be in the anelectro-
tonic, and that by the negative in the kathelectrotonic condition.
Therefore we have to study the —

I. Electro-motive alteration of the oxcitahility and conductiviiy.

li. Electro-motive alteration of the elect ro-motivity.

1. Electrotonic Variation of the Excitability.

A. (a.) Connect two small Grove's cells or two Panieil's to a
Pohl's commutator ivifh crosx-har.s (fig. 168), introducing a Du Bois
key to short-circuit the battery. From two of the binding screws
connect wires with two N.P. electrodes or the platinum electrodes
of Du Bois, introducing a sliort-circuiting key in the electrode
circuit (fig. 168).

I

244

PRACTICAL PHYSIOLOGY.

[XLVlir.

{h.) jNlake a nerve-muscle prepai'ation, attach a straw flag to the
foot, and fix the femur in a clamp, as in fig. i68. Lay the nerve
over the electrodes. Trace the direction of the current, and make
a mark to guide you as to when the current in the nerve is
descending or ascending, /.<'., whether the negative or positive pole
is next the muscle.

(f.) Place a drop of a saturated solution of common salt on tlie
nerve between -the electrodes and the muscle. In a minute or less

Fia. i68.— Scheme of Electrotnnlc Variation of Excitability. D. Drop of strong solution
of salt on the nerve, N ; F. Flag on the muscle.

the toes begin to twitch, and by-and-by the muscles of the leg
become tetanic, so that the flag is raised and kept in the horizontal
position.

('/.) Turn the commutator, so that the positive pole is next the
muscle ; the straw sinks, i.e., the excitability of the nerve in the
region of the positive pole is so diminished as to " block " the
impulse passing to the muscle, showing that the positive pole
lowers the excitability.

KlO. 169.— Sclienie of Electrotonic ^■a^iatilln of Excitability. P, P. Polarising,
and Ji, E. Stimulation current.

(^.) Reverse the commutator, so that the negative pole is next
the muscle. The limb becomes tetanic, the negative pole
{katlielectrotonic area) increases the excitability.

2. Another Method. —Apparatus. —Three Daniell's cells, two pairs of N.P.

elcctrdies, two Da Bois keys, a spring-key, commutator icith cross-bars,
induction coil, wires, moist chami)er. drum.

B. (r/.) Arrange the ajiparatus according to the scheme (fig. 169). Prepare
two jiairs ol N.P. electrodes lor the nerve.

XLVITI.] ELECTROTONUS. 245

(/'. ) Connect two Daniell's cells with a Pohl's commutator with cross-bars
(C) ; connect the commutator- a sliort-circuiting key intervening — to one
pair of the N.P. electrodes. This is tiie "polarising current" (P. P).

(f. ) Arrange an induction coil for tetanising shocks ; use N.P. electrodes
and short-circuit the secondary circuit. This is the "exciting current"
(E, E).

((/. ) Make a nerve-muscle preparation with the nerve as long as possible,
and arrange it to Avrite on a drum. Place the nerve on the two pairs of
electrodes in the moist chamber, the "polarising" pair being next the cut
end of the nerve (P, P), and about i centimetre aj)art. Between the polarising
jiair and the muscle apply the "exciting" pair of electrodes to the nerve
(E, E).

{c.} With the jiolarising current short-circuited, pull away the secondary
from the primary coil, and find the minimum distance at which a feeble con-
traction of the muscle is obtained. Push the secondary coil up until a weak
contraction is obtained, and take a tracing. Previously arrange the com-
mutator to send a descending current through the nerve. While the muscle
is contracting feebly, throw in the descending polarising current ; at once the
contraction becomes much stronger. Reverse the commutator to send an
ascinding polarising current through the nerve, and the contraction will
cease.

Fig. 170. — Ti-aciiig showing effect of Anode and Kathode on Excitaliility of Nerve, the
latter stimuhited with repeated shocks. T. Time in seconds.

(/.) Repeat the experiment, using Neefs hammer, selecting a strength of
stimulus just insufficient to give tetanic response when the -f pole of the polar-
ising current is next the muscle. Reverse the commutator, and at once the
previously inadequate shocks become adequate and tetanus results as shown
in tig. 170, where the effect of + and - poles are shown alternately.

In the first case, the area influenced by the exciting electrodes was affected
by the negative pole, i.e., was in the condition of kathelectrotonus, and the
tetanus was increased : therefore, the kathcbxtrotonic condition incnoses the
excitability of a nerve. In the second, the nerve next the exciting electrodes
was in the condition of anelectrotonus, and the contractions ceased ; therefore,
the anelectrotonic condition dirninisftes the excitability of a nerve (fig. 171).

3. Rheochord -use salt as stimulus. — The experiment may also be done by
using a rheochord to graduate the polarising current, salt again being used as
the stimulus.

{n.) Arrange two N.P. electrodes in a moist chamber, provided with a
recording lever, placing the N.P.'s about i cm. apart.

(b.) Connect the terminals of two Daniell's cells (arranged in circuit) to the
central .screws of a Pohl's commutator (with cross-bars) as in fig. 172, placing
a mercury key in the circuit. Connect the wires, x, y, to the two blocks on

246

PRACTICAL PHYSIOLOGY.

[XLVIII.

the rlieochord shown in fig. 92. By reversing the coiunautator the current
through the rheochord can be reversed. Then connect one N.F. electrode with
one terminal of the rheochord, while the other N.P. is connected with the
movable block or slider (S) of the rheochord.

(c. ) Notice which pole is next the muscle according to the position of the
commutator and make a mark to guide you. Make a long nerve-muscle and
arrange it over the electrodes, attaching the muscle to a recording lever
(crank).

Via. 171.— Scheme of Electrotonic Variation of Excitability in a Nerve. K. Kafiode ;
A. Anode ; N, n. Nerve. The curve above the line indicates increase, ami that below
the line decrease of excitability.

(d.) Begin with the slider (S) close up to the zero terminal, and gradually
slide it along until, on closing the battery circuit, the muscle res])onds at make
whether the -r or - pole is next the muscle, i.e., whether the current is
ascending or descending.

(c. ) Oj)en the circuit, place on the nerve near the muscle either a drop
of saturated solution of common salt or line moist crystals of salt. Wait till
the salt j)roduces occasional short spasmodic movements of the limb. Close
the key, i)lace the - pole next the muscle, at once the limb becomes tetanic
owing to the increase of excitability under the influence of the - pole {kath-
dectrotonus). Open the current, the limb becomes quiescent.

if.) Ojien the key, and
after a short time, when
the spasms reappear,
reverse the commutator
so that the + pole is next
the muscle. Close the
current, the limb becomes
quiescent, due to the fall
of excitability under the
influence of the + pole
(aneledrutoiins). Break
the current, the muscle
becomes tetanic. Thus it
is shown that the appear-
ance of kathelectrotonus and the disappearance of anelectrotonus are accom-
panied by increase of excitability, while the disap])earance of kathelectrotonus
and the appearance of anelectrotonus are accompanied by diminution of
excitability.

Fig. 172. — Pohl's Commutator with cross-bars, arranged
for reversing the direction of a current.

xux.]

PFLUGER S LAW OF CONTRACTION.

247.

4. Conductivity is impaired in the Intra-Polar Region.— Arrange the

experiment as in 3, but j)lace the salt on the nerve as far as jmssible from the
muscle. "Wlien the salt causes tetanic spasms, close the current through the
electrodes, and whether this current be ascending or descending, the spasms
cease, because the excitatory change is " blocked " in the intra-polar area.

LESSON XLIX.

PFLUGER'S LAW OP CONTRACTION— ELECTRO-
TONIC VARIATION OF THE ELECTRO-
MOTIVITY— RITTER'S TETANUS.

1. Pfluger's Law of Contraction. — Apparatus. — Several
Daniell or small Grove cells, commutator with cross-bars, Du
Bois and Hg-key, rheochord, N.P. electrodes, moist chamber, wires,
recording apparatus.

(a.) Arrange the apparatus as in the scheme (fig. 173). Connect
two Daniell or small Grove cells to a Pohl's commutator wit/i cross-

FiG. 173.— Scheme for Pflug-ers Law. B. Rheochord ; B. Battery ; C. Commutator;
A'. Meicury key ; A". Du Bois key ; E. N.P. Electrodes ; S. Nerve.

bin\<, and introduce a mercury key (K) into the circuit : connect
the commutator with the rheochord (R). Connect the rheochord
with N.P. electrodes, introducing a short-circuiting key. Fix to a
recording lever a nerve-muscle preparation — with a long nerve — in
the moist chamber, and lay the nerve over the electrodes.

{b.) Begin with all the plugs in position in the rheochord and
tlie slider hard up to the brass blocks. Place the commutator to
give an ascending current, make and break the current — gradually
adjusting the slider — until a contraction occurs at make and nonfe
at break. Reverse the commutator to get a descending current,
make and break, observing again a contraction at make and none at
break. This represents the effect of a tveak current. Sometimes

248

PRACTICAL PHYSIOLOGY.

[XLTX.

the ciu-rent so obtained is not weak enough. The simple rheocliord
should then be used (p. 163).

(c.) Pull the slider farther away and remove one or more plugs
until contraction is obtained at make and break, both with an
ascending and descendijig current. This represents the effect of a
rne-Hum current.

{d.) Use six small Grove's cells, take out all the plugs from tlie
rheochord, and with the current ascending, contraction occurs at
break only ; while witli a descending current, contraction occurs
only at make. This represents the effect of a strong current.
Tabulate the results in each case.

For this experiment very fresh and strong frogs are necessary, and several
preparations may be re/juired to woik out all the details of the law. Instead
of reversing the commutator after testing the effect of an alteration of the
direction of the current, the student may use one preparation to test at
intervals the effect of weak, medium, and strong currents when the current
is ascending, and a second preparation to test the results witli currents of
varying intensity when the current is descending. The results may be
tabulated as follows : R ^ rest ; C = contraction : —

Strength of Current.

Ascending.

Descending.

On Making.

On Breaking.

On Making.

On Breaking.

Weak, .

c

R

c

R

Medium,

c

C

c

C

Strong, .

R

C

c

R

2. Electrotonic Variation of the Electro-motivity.

(o.) Arrange a long nerve on N.P. p'cctrodes, as for determining its demar-
cation-current. Place the free end ot the nerve on a ])air of N.P. electrodes
— the polarising cuirent— arranged as in Lesson XLVIII., so that the cun-ent
can be made ascending or descending.

(6.) Take the deflection of the galvanometer needle or demarcation-cun-ent
when the ]>olarising current is shut off. Throw in a descending ])olarising
current, and observe that the spot of light travels towards zero. Reverse the
commutator and throw in an ascending current, tlie spot of light shows a
greater positive variation than before. From this we conclude that knthe-
/cctrotomts dii)iinishi;s the elcctro-inotivUy. irhilc. avcleclrotonns incretuses it.
In the extra-jiolar Uathodic region an electrotonic current ajijiears when the
polarising current is closed. It has the same direction as the ])olarising
curi'ent. In the anodic region the direction is also that of the ])olarising
current ; but tlie electrotonic current is stronger than the kathodic current.
If a demarcation-current exists already, the electrotonic currents are super-
posed on it.

XLIX.]

pfluoer's law of contraction.

249

3. Ritter's Tetaniis.

(«. ) Connect three Daniell's cells witli N.P. electrodes, short-circuiting
with a Du Hois key. Make a nerveiiiiiscle jjrejiaration, and iil>l)ly the
electrodes to the nerve so that the + pole is next the muscle, i.e., the current
is ascending in the nerve. Allow the current to circulate in the nerve for
some time (usually about live minutes is sufficient), no contraction takes
place. Short-circuit, and the muscle becomes tetanic.

{h.) Divide the nerve between the electrodes, and the tetanus does not
cease ; but on dividing it between the + pole and the muscle, the tetanus
ceases. Therefore the tetanus is due to some condition at the positive pole,
?>. , the stimulation proceeds from the positive pole at break.

4, Eathodic Stimulus is the more powerful.

{a.) Let the M. and B. shocks be made approximately equal by the arrange-
ment shown in tig. 174. In the secondary circuit place a Pohl's commutator

Fig. 174. — Scheme to show that Kathodio Stimulation ia the more powerful. K. Key ;
R. Commutator ; F. Frog's leg ; c. One electrode.

with cross-bars (R). Place one electrode (c) under the sciatic nerve, and the
ocher on another part of the body.

(/). ) Sup])Ose c to be the catliode, select a strength of shock, i.e., distance
of secondary from jjiiniary coil, so that there is response on breaking the
primary current. Reverse the commutator so that c becomes the anode.
There is no muscular response at break, but it occurs at make, as c is then
the cathode.

5. Rheochord of Du Bois-Reymond is used to vary the amount of a
amstdiit nirreni applied to a muscle or nerve (fig. 175). It consists of a long
box, with German-silver wire —of varying length, and whose resistance is
accurately graduated — stretclied upon it. At one end are a series of brass
blocks disconnected with each other above, but connected below by a German-
silver wire jiassing round a pin. These blocks, however, may be connected
directly by brass ])lugs, S| So . . . S^. From tlie blocks i and 2 two jilatinum
wires pass from A to the o}>])osite eml of the box (Y), where they are insu
lated. Between the wires is a "slider" (L), consisting ol two brass cups
containing mercury, which slide along the wires.

250

PRACTICAL PHYSIOLOGY.

[I.

In using the instrument, connect a Daniell's cell to the binding screws at
A and B, and to the same screws attach the wires of the electrodes over

which the nerve (c d) of the muscle
(F) is laid. We have two circuits
{a c d b and « A B 6) ; the wires of
the rheochord are introduced into the
latter.

Push up the slider with its cups (L)
until it touches the two brass plates
I and 2, and insert all the plugs
(S|-Sg) in their places, thus making
the several blocks of brass practically
one block. In this position, tlie zero
of the instrument, the resistance offered
by the rheochord circuit is so small as
compared with that including the nerve,
that practically all the electricity passes
through the former and none through
the latter.

Move the slider away fi'om A, when
a resistance is thrown into the rheo-
chord circuit, according to the length
of the platinum wires thus introduced
into it, and so a certain fraction of the
current is sent through the electrode
circuit. If the plug S, be taken out,
more resistance is introduced, that due
to the German silver wire (I b), and,
therefore, a certain amount of the
current is made to pass through the
electrode circuit. By taking out plug
after i>lug more and more resistance is
thrown into the rheochord circuit. The
plugs are numbered, and the diameter
and length of the German-silver wires
are so selected in making the instru-
ment, that the resistances rej)resented
by the several plugs when removed are all multiples of the resistance
in the platinum wires on which tlie slider moves. Proceed taking out plug
after plug, and note tlie result. The result, and explanation thereof, are
referred to in Lesson XLIX. 1.

Fig. 175.— Rheochord of Du
Bdis-Eeyniond.

LESSON L.

VELOCITY OF NERVE-IMPULSE IN FROG, MAN-
DOUBLE CONDUCTION IN NERVE— KUHNE'S
GRACILIS EXPERIMENT, &c.

1. Velocity of Nerve Energy in a Frog's Motor Nerve.

The rate of propagation of a norve-impulse or excitatory change
may be estimated by eitlier the pendulum or spring-myograph.

L.]

VELOCITY OF NERVE-IMPULSE.

251

With slight modifications the two processes are identical, only in
using the spving-myograph it is necessary to wse such a coiled spring
as ■will cause the glass plate to move Avith sullicient rapidity to give
an interval long enough for the estimation of the latent period. It
may be done also on a revolving drum provided the drum moves
with sufficient rapidity.

(a.) Use the spring-myogi'aph and arrange the experiment
according to the scheme (fig. 176), i.e., an induction coil for single
shocks -with the trigger-key of the myograph (i, 2) in the primary
circuit ; in the secondary circuit (which should be short-circuited,
not represented in the diagram) place a Pohl's commutator icithout
c.wss-hars (C). Two pairs of wires from the commutator pass to
two pairs of electrodes {a, b), arranged on a bar in the moist
chamber. Measure the distance between the electrodes.

I Ji

Fig. 176.— Scheme for Estimating the Velocity of Nerve-Energy,

[h.) Make a nerve-muscle preparation with a long nerve (N),
clamp the femur (/"), attach the tendon {m) to a writing-lever, and
lay the nerve over the electrodes, the distance between them being
known. It is well to cool the nerve by iced normal saline, as the
velocity of the itnpulse is thereby much diminished.

{c.) Arrange the glass plate covered with smoked paper, adjust
the lever to mark on the glass, close the trigger-key in the primary
circuit, and unshort-circuit the secondary. Turn the bridge of the
commutator so that the stimulus will be sent through the electrodes
next the muscle {a). Press the thumb plate, the glass plate shoots
across. The tooth (3) breaks the primary circuit, and a curve is
inscribed on the plate.

{(i.) Short-circuit again, replace the glass plate, close the trigger-
key, reverse the commutator. This time the stimulus will pass

252 PRACTICAL PHYSIOLOGY. [L.

through the electrodes away from the muscle (h). Unshort-circuit
the secondary circuit, and shoot the glass plate, when another
curve will he inscribed, this time a Htt/e lafur than the first one.

(e.) Replace the glass plate, close the trigger-key, short-circuit
the secondary circuit, and shoot the plate. This makes the abscissa.

(f.) Replace the glass plate, close the trigger-key, and bring the
tooth of the glass plate (3) just to touch the trigger-key ; raise the
writing-lever to make a vertical mark. This indicates the moment
wlien the stimulus was thrown into both points of the nerve.

(.'/.) Remove the moist chamber, push up the glass plate, close
the trigger-key, and arrange a tuning-fork vibrating 250 D.V. per
second to write under the abscissa. Shoot the plate again and the
time-curve will be obtained. Fix the tracing, draw ordinates from
the beginning of the curves obtained by the stimulation of a and b
respectively, measure the time between them from the time-curve
(this gives the time the impulse took to travel from h to a), and
calculate the velocity from the data obtained.

Example. — Suppose the length of nerve to be 4 cm., and the time
required for tlie impulse to travel from & to a to be ^i^ sec. Then
we have 4 : 100 : -^^q" : -^", or 30 metres (about 98 feet) per
second, as the velocity of nerve-energy along a nerve.

2. Repeat the observation with the pendulum-myogi'aph.
Practically the same arrangements are necessary.

If it be desired to test the effect of heat or cold on the rapidity
of propagation, the nerve must be laid on ebonite electrodes, made
in the form of a chamber, and covered wdth a lacquered copper
plate on which the nerve rests. Through the chamber water at
different temperatures can be passed, and the effect on the rate of
propagation observed.

3. Velocity of Motor Nerve-Impulse in Man.

(a.) Use a pendulum-myograph. Connect two Daniell's cells
witli the primary circuit of an induction coil and interpose in the
circuit the trigger-key of the myograph, which the pendulum opens
in swinging past. Place a sliort-circuiting key in the secondary
circuit, and to the sliort-circuiting key attach a pair of rheophores
moistened with strung solution of salt.

(h.) An':\ngQ~^\a,rfiy's '^ }»'nre myorp-ap/iiqiie " {f[g. 151) to compress
the adductor muscles of the thumb wlien tlie latter is in tjie
abducted position. Connect the " pince " by means of an india-
rubber tube with a INIaroy's tambour (fig. 150) arranged to record
its mov^ements on glazed paper fixed to the plate of the pendulum-
myograph.

(c.) The nerve supplying t)ie adductor muscles of the thumb

L.] VELOCITY OF NEHVE-IMPULSE. 253

must be stimulated first near the ball of the thumb, and secondly
at the bend of tlie elbow. Contraction takes place sooner from the
former than from tlie latter position. Suppose the right thumb to
be u.sed, apply one rheophore to tlie right side of the chest, and
the other to just over the ball of the thumb. Allow the pendulum
to swing. Take a tracing. Replace pendulum, sliort-circuit the
secondary circuit, close the trigger-key.

(d.) Open the secondary circuit. Apply the arm rheophore to
the median nerve at the bend of the elbow and record another
contraction.

(e.) Record a base-line and mark the point of stimulation on the
myograph plate. Make a time-tracing under the two muscle curves.

(/'.) Pleasure the distance between (i.) the two arm electrodes ;
(ii.) the beginning of the two curves; (iii.) note the time-value of
(ii.) as indicated by the time curve ; and from these data calculate
the time the nervous impulse took to travel from the elbow to
the nerve supplying the muscles of the ball of the thumb.

ADDITIONAL EXERCISES.

4. Double Conduction in Nerve— Kuhne's Experiment on the Gracilis. —

The gracilis is divided into a larger and smaller portion (LI by a tendinous
inscription (K) running across it(fig. 177). The nerve (X) enters at the hilum
in the larger half, and bifurcates, giving a branch (/.) to the smaller portion,
and another to the larger portion of the muscle, but neither branch reaches
quite to the end of either half of the muscle.

(a.) Remove tlie gracilis (rectus internus major and minor)
(Ecker). The method of removing semi-raembranosus and gracilis
together has already been described (Lesson ^_^

XXIX. 5). Place a pithed and skinned frog on /^\
its back. In order to see the outline of the thigh A ] ^\
muscles better, moisten them with blood. The / ^>c/
sartorius by its inner margin lies in relation with \ /f.^^^^
the gracilis near its lower attachment, the graciUs :' /^^\~^^iT
itself lying on the ventral surface of the inner '\Jy] \l ^'"^
part of the thigh, having its origin at the sym- ^y ( I
physis, and its insertion at the tibia. The suiall \ (^ /
part — minor — is attached to the skin and is "•L/

usually torn through when the skin is removed, rio. 177.— Kiihne'a
By its other margin it is in contact with the semi- tluf Gracilis,
membranosus. The muscle is detached from below
upwards. Its tendinous inscription or intersection is readily visible
on a black surface.

2 54 PRACTICAL PHYSIOLOGY. [hi.

{b.) Cut it as in fig. 177, avoiding injury to the nerves, so that only the
nerve twig (k) connects the larger and smaller halves, and in one tongue (Z)
terminates a nerve. After excision lay it on a glass plate with a bkuk back-
ground, else one does not see clearly the inscription and the course of the
nerves.

{c.) Stimulate the tongue (Z) with fine electrodes about i mm. apart, and
contraction occurs in both L and K. This, according to Kiihne. is due to
centripetal conduction in a motor nerve. This experiment is adduced by him
as the best proof of double conduction in nerve fibres. Mays has shown that
the nerve fibre divides and supplies both halves of the muscle.

(if.) If the muscle be exposed in a curarised frog, on stimulating
either half of the muscle with repeated shocks, only that half
responds, as the inscription blocks the passage of the muscle-wave.

{e.) If an uncurarised muscle is used, stimulation of the muscle
near its ends causes response only in its own half. Why 1 Because
there are no nerves there ; but stimulation near the inscription
causes response in both halves. Why 1 Because they are excited
through their nerves, as shown definitely by (c.),

5. Action of a Constant Current — In muscle and nerve, stimulation occurs
onlti at the kathode uhcn the current is made (closed), and at the anode when it
is broken (ojjcned) — {F, Bczold). This is most readily seen in fatigued
muscles.

(A.) Engelmann's Experiment. — [a.) Suspend vertically a curarised sar-
torius of a frog, and ])ass a constant current through its upper extremity.
On making the current, the muscle moves towards the side of the kathode,
because contraction occurs at the kathode on making. At break, it inclines
to the anode. '

(6.) Slit up the muscle longitudinally, so tliat it looks like a pair of
trousers, and keep the two legs, as it were, asunder by an insulating medium ;
at make, the kathodic half alone contracts ; at break, the anodic half.

(B. ) Another Method. — Dissect out the sartorius of a curarised frog, but
remove it with its bony attachments, clamp it at its centre, and arrange it
either vertically as in fig. 191, attaching its ends to two recording levers
I)laced one above it and the other below it, or fix it on a double crank-myo-
graph. Pass thin wires fi'om the battery through the two ends of the muscle ;
on making the current, the lever attached to the kathode rises before the
other, i.e., where the current leaves the muscle. On breaking the current,
the anodic lever rises first, showing that the anodic half contracts before the
kathodic half.

LESSON LI.

OTHER CONDITIONS AFFECTING THE EXCITA-
BILITY OF NERVE — CHEMICAL, TEMPERA-
TURE, &c.

1. Unequal Excitability of Different Portions of a Motor
Nerve. — Apparatus. — Cell, two keys, wires, commutator, induction
coil, either for single or faradic shocks, two pairs of electrodes.

LL]

EXCITABILITY OF XERVE.

255

(a.) Arrange the apparatus as in fig. 178. Dissect out the whole
length of the sciatic nerve witli the leg attached. Lay the nerve
on two pairs of electrodes, A and B, one near the muscle and the
other away from it, and as far apart as possible. Two pairs of
wires thrust through a cork will do quite well.

(h.) Stimulate at A with a current that gives a minimal contrac-
tion. Reverse the commutator. Stimulate at B, a stronger
contraction is obtained, because the excitability of a nerve is
greater farther from a muscle or nearer the centre. Instead of
using single shocks, repeated shocks by means of Xeef's hammer
may be used.

Fia. 178. — Scheme for the Unequal Excitability of a Xerve.

2. Effect of Temperature on Excitability of a Nerve,

((7.) Fix a nerve-muscle preparation on a crank-myograph, so as
to record on a revolving cylinder provided with an automatic break-
key placed in tlie primary circuit of an induction coil, and so
arranged as to give only feeble break shocks.

{L>.) Bring a test-tube filled with Avater at 80-90' C. near the
nerve, where the electrodes lie on it. Soon the contraction
increases and may become maximal.

(('.) Eemove the source of heat and the contractions become less,
i.e. , the excitability falls.

('/.) Similar results may be obtained by the direct application
of warm normal saline to a nerve.

(For other kinds of nerve fibres see " P^ttects of stinudation and
of changes in temperature upon irritability and conductivity of
nerve fibres," by Howell and others, Journal of IVii/sio/otji/, xvi.
p. 298.)

3. Salt Increases the Excitability of a Nerve.

(a.) Arrange a nerve-muscle preparation as in 2, and determine

256 PRACTICAL PHYSIOLOGY. [LL

the distance of the secondary from the primary coil to obtain a
minimal stimulus, i.e., response. Apply a drop of saturated solution
of common salt to the nerve betweeji the electrodes and the muscle.
Almost at once the excitability of the nerve is increased, as shown
by the height of the contraction, so that the excitability increases
at once.

{I>.) After several minutes the nmscles begin to twitch, the salt
acting as a chemical stimulus. Tt is thus evident that the excita-
bility is early increased, but before muscular response to chemical
stimulation is elicited a considerable time elapses.

4. Effect of Section on the Excitability of a Nerve.

{a.) Arrange a coil for single shocks, expose the sciatic nerve
in a pithed frog, and under it, near its central end, place insulated
electrodes, using single break shocks. Ascertain the distance of
the secondary from the primary coil at which the break shock is
just too weak to cause the muscles to respond (sub-minimal).

{!>.) With a sharp pair of scissors divide the sciatic nerve on the
central side of the electrodes. The stimulus (previously sub-minimal)
now causes a strong contraction.

(c.) Ascertain the distance (perhaps several cm.) to which the
secondary coil must be pushed away from the primary in order to
obtain again a sub-minimal stimulus. The condition of increased
excitability lasts for some time.

5. Excitability of Flexors and Extensors (Rollett).

Arrange a coil for repeated shocks. Expose either the sciatic
nerve or the sciatic plexus in a pithed frog. Select a weak
current, and flexion of the leg muscles is obtained ; on pushing up
the secondary coil, the extensors prevail.

6. Functions of Different Motor Nerves (Sciatic Plexus).
Strip off the skin from the hind-legs of a pithed frog. Open

the abdomen and expose the sciatic plexus, the frog being placed
on its back. Stimulate with faradic electricity — selecting a
strength of current just adequate to yield a muscular response —
each of the three cords forming the sciatic plexus. The upper cord
supplies muscles acting chiefly on the hip-joint, the lowest acts
chiefly on the muscles moving the ankle and toes, and the middle
one on the muscles acting on the knee-joint.

7. Conductivity /•. Excitability (Grunhagen's Experiment),
(a.) Pass the nerve of a frog's leg through a glass tube (fig. 179),

sealing the ends with clay, but not compressing the nerve. The
tube is supplied with an inlet and outlet, to which elastic tubes can

LI.]

EXCITABILTTT OF NERVE.

257

be attached and through which vapours or gases can be passed, and
also with electrodes so tliat the u-^.rve can be stimulated witliin or
outside the tube. Use a Pohl's ooianiutator for this purpose.

{/>.) Pass CO.i from a Kipp's a})paratus through the tube; on
stimulating the nerve at A 1

with repeated shocks, there is
no response, but on stimulating
at B there is. Find a strength
of stimulus which just excites
the nerve at A and B. On
passing CO, A no longer re-
sponds to tliis stimulus, but
recjuires a stronger stimulus, or
it may not respond at all. It
would seem that the excitatory
change set up at B is propagated
through A, although its excita-
bility is ver)'' feeble or nil. It
thus seems to conduct, even
though it is inexcitable.

('•.) On passing the vapour of
alcohol the conductivity appears to vanish before the excitability.
It is better to suck the vapour through by means of any form of
exhaust pump. The results, however, may be capable of a different
interpretation. (Gad, D71 Bnis-Ret/rnand's Archie, 1888, p. 395,
and 1889, p. 350; Piotrowski, " Trennung d. Reizbark. v
Leitungsfah. d. Nerven," ildd., 1893, p. 205.)

{(l.) Cold. — Apply cold to a nerve as in 8, i.e., lay the nerve over
a glass tube through which cold water is conducted. Cold, like
CO.,, abolishes or diminishes the excitability, but not the con-
ductivity.

The action of other substances, such as chloroform, ether, and
CO, have been investigated.

Fig. 179.— GninhaRen's Experiment on
Conductivity >•. Excitability.

ADDITIONAL EXEfvCCSES.

, 8. Influence of Localised CJold upon Excita'iili y (Gotcha

A. Upon Nerve.

The influence of changes in temperature upon excitability can be investi-
gated by arranging in the moist chamber a gUss tube placed at right angles
to the nerve of a nerve-muscle preparation, aiid situated so that a small
portion of the nerve shall lie athwart the tube. Through the tube water at
temjjeratures varied at will from 10° to 30° C. is allowed to flow.

The alteration in temperature cavses a viarkad alteraii&n in the electrical

25S I'RACtlCAL PHYSIOLOGY. [lI.

resistance of the tlt^suc, this being lowered by warmtli and raised by cold ; in
crdi-r to get rid of this purely physical change, it is essential that a large
resistance should be introduced into the exciting circuit. This is most
simply done by using non-polarisable electrodes with threads attached to the
ends of the electrodes ke})t moist by normal saline solution. The threads are
now arranged so as to touch the. nerve where it lies on the tube, one thread
being placed so that the contact shall be on tlie edge of the cooling tube
nearest the muscle. The simplest method of exciting the nerve is by means
of a weak galvanic current. For this ])urpose the rheochord is used and a
weak curri-nt employed of such direction that it shall descend the nerve and
thus excite this at the cathodic contact on the distal edge of the glass tube.

In order to ensure that the galvanic current is always of the same duration,
it is desirable to close the cui'rent by an automatic arrangement, either a
revolving drum carrying a striker which shall at each revolution strike a
stretched wire, or a metronome ; but the influence of the tem])erature alteration
may be obtained without this arrangement, the closure being effected by a
Pohl's reverser without cross lines as a double make mercurial key worked by
tlie hand.

The nerve-muscle preparation having been made and the muscle attached
to an appropriate lever, so as to record its contraction upon a \ ery slowly
moving surface, an intensity of current is ascertained, which, with the nerve
at the normal temperature of the room, is only just adequate to evoke a very
weak minimal muscular response whenever the circuit is closed.

The tempeiature of the nerve is now raised by allowing water at 30° C. to
pass through the tube, when the response will disajipear ; the temperature is
now lowered by allowing water at 10" C. or less to flow — the response is now
very marked. Localised cold thus increases the excitability of nerve to this
form of stimulus. Similar effects can be obtained with the condenser dis
charge, with mechanical and with chemical stimuli. If the induction
current is used instead of tlie galvanic current, a reverse effect is obtained,
the nerve-muscle preparation responding better when the excited nerve is at
30" C. ; and this favourable influence of warmth ])ersists even when a very
large external resistance is introduced into the circuit.

B. Ui'on Muscle.

The sartorius muscle of the frog is used for this experiment, the threads of
the exciting electrodes being jilaced upon the broad "nerveless" jielvic end
of the muscle under whicli tlie tube of the cooling arrangement is fixed. It
is then found that the muscle responds better when cooled to every form of
stimulus applied to the cooled region, including the induction current. If
the electrodes be shifted to the "nerved" ])ortion of muscle, the response,
being indirect, is disfavoured by cold when the induction current is used. —
(Communiadcd by I'rojessor Gotch.) See also Journal of I'hys., XII.

LII.] THE frog's heart. 259

PHYSIOLOGY OF THE CIRCULATION.

LESSON LII.

THE FROG'S HEART— BEATING OF THE HEART-
EFFECT OF HEAT AND COLD— SECTION OF
THE HEART.

1. Heart of the Frog and how to Expose it.

(a.) Pith a frog, and lay it on its back and pin out its legs on
a frog-plate. ISIake a median incision through the skin over the
sternum, continue the incision upwards and downwards, and from
the middle of the sternum make transverse incisions.

(b.) Reflect the four flaps of skin, raise the lower end of the
episternum with a pair of forceps, and cut through the sternal carti-
lage just above its lower end, to avoid wounding the epigastric
vein. With a strong pair of scissors cut along the margins of the
sternum, and divide it above. Do not injure the heart, which is
exposed still beating within its pericardium.

(c.) With a fine pair of forceps carefully lift up the thin trans-
parent pericardium, and cut it open, thus exposing the heart.

2. General Arrangement of the Frog's Heart.

(a.) Observe its shape, noting the two auricles above (fig. i8o,
Ad, As), and the conical apex of the single ventricle below (v), the
auricles being mapped oft" from the ventricle by a groove which
runs obliquely across its anterior aspect. The ventricle is con-
tinuous anteriorly with the bulbus aortge (B), which projects in
front of the right auricle, and divides into two aortae — right and
left, the left being the larger.

(b.) Tilt up the ventricle and observe the sinus venosus (fig.
i8i, s.z;.) continuous with the right auricle, and formed by the
junction of the large inferior vena cava (c.i.) and the two (smaller)
superior vense cavse {c.s\s, c.s.d).

3. Note the sequence of contraction of the several parts, viz.,
sinus venosus, auricles, ventricle, and bulbus arteriosus.

This sequence of events is difiicult to note, but what can be
easily observed is the relative condition of vascularity of the
ventricle. The frog's ventricle has no blood-vessels supplying its
muscular walls. Note that during systole of the ventricle, i.e.,
during its contraction, it becomes pale, and immediately thereafter,

26o

PRACTICAL PHYSIOLOGY.

[LIL

during its diastole, it is distended with blood and has a red appear-
ance, the blood flowing into it being propelled by the contracting
auricles. Notice also how the position of the auriculo- ventricular
groove moves upwards and downwards during each cardiac cycle.
Xote the normal rhythm, i.e., the number of beats per minute.

4. Effect of Temperature (Heart in situ).

(a.) By means of a pipette allow a few drops of normal saline at
20°-2 5° C. to bathe the heart, and note how rapidly the number
of beats, i.e., rhythm, is increased, and how each individual beat
is quicker.

c.sd.

-.A.d.

Fig. i8o. — Frog's Heart
from tlie Front, v. Single
ventricle; Ad, As. Right
and left auricles ; B.
Bulbus arteriosus ; i.
Carotid ; 2. Aorta ; 3.
Pulmo- cutaneous arte-
ries ; C. Carotid i,rland.

Fig. 181.— Heart of Frog from Behind.
B.v. Sinus venosus opened; c.i. In-
ferior, c.s.d, c.s.s. Kight and left
superior venae cava ; v.p. Pulmonary
vein ; A.d, and A.s. Right and left
auricles ; A. p. Communication be-
tween the right and left auricle.

(h.) Then apply normal saline at 10° C. or 5° C, and note the
opposite effect on the rate or rhythm, together with the slower
contraction of each individual beat.

5. An Excised Heart Beats.

(a.) With a seeker tilt up the apex of the ventricle, and observe
that a thin thread of connective tissue, called the " frgenum,"
containing a small vein, passes from the pericardium to the posterior
aspect of the ventricle. Tie a fine silk thread round the fraenum
and divide it dorsal to the ligature. Count the number of beats
per minute. By means of the silk thread raise the heart as a
whole, and with a sharp pair of scissors cut out the heart by divid-
ing the inferior vena cava, the two superior vense cavae, and the
two aortge. Place the excised heart in a watch-glass, and cover it
with another watch-glass.

(h.) The heart goes on beating. Count the number of beats per
minute. Therefore its beat is automatic, and the heart contains
within itself the mechanism for originating and keeping up its
rhythmical beats.

LII.] THE frog's heart. 26 1

• (c) Place the heart on a microscopical sHde and note that during
diastole it is soft and flaccid, and adjusts itself to any surface it may
rest on. During systole, i.e., when it contracts, its apex is raised
and erected.

6. Heat and Cold on the Excised Heart.

(a.) Place the watch-glass containing the heating heart on the
palm of the hand, and the heart heats faster ; or place it on a hoaker
containing warm water, which must not be above 40° C. Xote
that, as the temperature of the heart rises, it beats faster — there are
more beats per minute — therefore each single beat is faster.

ih.) Place the watch-glass and heart over a beaker containing iced
water, the number of beats diminishes, each beat being executed
move slowly and sluggishly.

7. Section of the Heart.

(a.) Expose the heart, divide tlie pericardium, and ligature the
fraenum, and liy means of it gentlj' raise the heart. "With scissors
excise the wliole heart, including the sinus venosus. The heart still
beats.

(6.) Cut off the sinus ; it continues to beat. The rest of the
heart ceases to b<5at for a time, but by-and-l»y it commences to beat
rhythmically.

(c.) Sever the auricles from the ventricle; the ventricle ceases
to beat. The ventricle, however, has not lost the power of beating
rhythmically. To prove this, stimulate it mechanically, e.;j., by
pricking it with a needle. After an appreciable latent period, it
executes one — generally several — beats, and then becomes quiescent.
Stimulate with a single induction shock, this also causes it to dis-
charge one or more Ijeats.

{'L) Cut oft' the apex of the ventricle ; it remains quiescent ; but
if it be stimulated, either mechanically or electrically, it makes a
single beat— not a series, as in the case of {c).

(e.) Divide the ventricle of another heart below the auriculo-
ventricular groove. The auricles, with the upper part of the ventricle
attached, continue to boat, while the lower two-thirds no longer
beats spontaneously. If it be pricked with a needle, however, it
contracts as often as it is stimulated mechanically. It responds by a
single contraction to a single stimulus, but a single stimulus does
not excite a series of rliythmical contractions.

(/'.) "With scissors divide longitudinally the auricles with the
attached portion of the ventricle, tlach half contracts spontaneously,
although the rhythm may not be the same in both.

{g.) Instead of cutting, one may use a ligature, or the heart apex may be
separated by Bernstein's method, viz., compress the heart above its apex

262 PRACTICAL PHYSIOLOGY. [lIII.

by forceps, so as to break the j)liysiological continuity but not the physical,
both j)arts remaining connected with each other. In a pulsating heart, all
pulsates exce])t tlie apex. It the bulbus aortiu be compressed so as to raise
the pressure within the apex, the apex also beats.

8. Movements of the Heart. — Expose the heart of a freshly
pithed frog as directed in Lesson LII., or better still, destroy only
tlie brain and then curarise the frog. Observe

(a.) Tliat the auricles contract synchronously and force their
blood into the ventricle, which, from being pale and flaccid, becomes
red, turgid, and distended with blood.

{/>.) That immediately thereafter the ventricle suddenly contracts,
and forces the blood into the bulbus aortse, at the same time becom-
ing pale, while its apex is tilted forwards and upwards. As the
auricles continue to fill during the systole of the ventricle, on
superficial observation it might seem as if the blood were driven to
and fro between the auricles and ventricle, but careful observation
will soon satisfy one that this is not the case. Observe very care-
fully how the position of the auriculo-ventricular groove varies
during the several phases of cardiac activity.

(r.) The slight contraction of the bulbus aortae immediately
following the ventricular systole.

{d.) The diastolic phase or pause when the whole heart is at rest
before the auricles begin to contract. Ligature the fraenum and
divide it, gently raise up the ventricle by the ligature attached
to the fraenum, and observe the sinus venosus.

(e.) The peristaltic wave, or wave of contraction, begins at the
upper end of the vena cava inferior and sinus venosus ; it extends
to the auricles, which contract, then comes the ventricular systole
and that of the bulbus aortae, and finally the pause ; when the whole
sequence of events begins again with the systole of the sinus.

(/'.) Before the ventricular systole is complete the sinus is full,
while the auricles are filling.

All this is easier to describe than to observe, and it requires
patient and intelligent observation to assure oneself of the succes-
sion of events.

LESSON LIIL

GRAPHIC RECORD OF THE PROG'S HEART-
BEAT—EFFECT OF TEMPERATURE.

1. Graphic Eecord of the Frog's Heart (Direct registration
with lever).

(a.) Destroy the brain of a frog ; curarise it. Expose the heart,

LTir.]

THE FROGS HEART-BEAT.

263

still within its pericardium, and arrange a heart-lever so that it rests
lightly on the j^ericardium over the beating heart. Adjust the
lever to Avrite on a revolving cylinder, moving at a suitable rate
(5-6 cm. per second). Take a tracing of the beating of the heart.

(6.) Before commencing the experiment, make a suitable heart-lever with
a straw about 12 inches long, or a thin strip of wood about the same length.
Thrust a needle transversely eitlier through the straw or through a piece of
coik slipped over the straw about 2 inches from one end of the lever. The
needle forms the fulcrum of the lever, and works in bearings, whose height
can be adjusted. To the end of the lever nearest this is attached, at right
angles, a needle with a small piece of cork on its free end. The lever is so
adjusted that the cork on the needle rests on the heart. The long arm of the
lever is ])rovided with a writing-style of copper-foil, or a writing point made
of jiarchinent paper, fixed to it with sealing-wax. By using a long lever a
suthcient excursion is obtained. Another form of heart-lever is shown in fig.
182. It consists of a thin glass rod, fixed as shown in the Kgure. The frog is
laid on its back on a frog-j)late covered with cork. The heartdever is fixed
into the cork by means of the two pins (6), while C is so adjusted as to rest on
the heart.

Fio. 182.— Simple Frog's Heart-Lever, a. Fulcrnm ; L. Glass lever with knob to act as
counterpoise ; b. To fix the apparatus into the cork of a frog-plate ; C. Cork to rest on
the heart.

(c.) Open the pericardium, expose the heart, and adjust the
cork on the lever. To obtain a good tracing, it is w(dl to put a
resistant body behind the heart. Raise the ventricle, ligature the
frsenum, and divide the latter dorsal to the ligature; behind the
heart place a pad of blotting-
paper moistened with normal
saline, or a tliin glass-cover
slip. Adjust the cork pad of
the lever on tlie junction of
the auricles and ventricle, to
write on the drum, moving at
a slow rate (5-6 cm. per
second), and take a tracing.
Fix the tracing (fig. 183).

(d.) In the tracing note a
first ascent, due to tlie auricular contraction, and succeeding this a
second ascent, due to the contraction of the ventricle, followed by
a slow subsidence, due to the continuation of the ventricular
systole, and then a sudden descent, due to the diastolic relaxation
of the heart.

Fig. 183. — Tracing taken with a Frog's Heart-
Lever resting on the Auriculo-ventricular
Groove. .4. Heart tracing ; T. Time; each
interval represents one second.

264 PRACTICAL PHYSIOLOGY. [lIIL

2. Auricular Contraction. — Take a tracing with the lever
adjusted on the auricles alone, and avoid the bulbus aortse. Note
the smaller excursion of the lever. ,

3. Ventricular Contract '.on. — Adjust the lever so as to obtain
a tracing of the ventricular movements only.

4. In the above experiments arrange an electro-magnetic time-
marker or chronograph under the recording lever, so that the points
of tlie recording lever and time-marker write exactly in the same
vertical line. Thus one can calculate the time-relations of any part
of the curve.

5. Effect of Temperature on the Excised Heart.

(a.) Excise the heart of a pithed frog, lay it on an apparatus like
that in fig. 119. Fix india-rubber tubes to the inlet and outlet
tubes of the cooling box, the inlet tube passing from a funnel fixed

WIAAAJVIVPJV

J\AJ\J\j\j\AAjv^M^^'^-^^-'>'^'^^^

Via. 184. — Parts of a Tracing ttken from an Excised Frog's Heart. Tlie temperature
was ino'eased gradually from left to right of the curve.

in a stand above the box, and the outlet tube discharging into a
vessel below it. Ailjust the heart-lever to record the movements
of the contracting ventricle on a slowly-revolving drum. If the
heart tends to become dry, moisten it with normal saline mixed
with blood. Adjust a time-marker. Take a tracing.

(6.) Pass water from io°-20° C through the cooling-box, noting
the effect on the number of contractions, and the duration, height,
and form of each single beat.

(c.) The heart may be placed on a metallic support and gradually heated
by means of a spirit-lamp or other means. Fig. 184 shows how the shape,
size, amplitude, and number of heart-beats varies with a rise of temperature,
the temperature being lowest towards the left end of the tracing, and rising
as the tracing was taken.

LIII.]

THE FRCiGS HEART-BEAT.

265

ADDITIONAL EXERCISES.
6. Another form of heart-lever is shown in fig. 185.

Fig. 185. — Marey's Heart-Lever, as made by Verdiu.

7. In order to record simultaneously the contractions of auricles and ven-
tricle, and to study the relations of these events one to the other, a lever
must be placed on the auricles and another on the ventricle, and the points

Fig. 186.— Auricular and Ventricular Lever for the Heart of a Turtle or
Tortoise. Made by Verdin.

of both must be arranged so that the one writes directly over the other as
shown in fig. 186, in the heart of a turtle or tortoise.

266

PRACTICAL PHYSIOLOGY.

[LIV.

LESSON LIV.

SUSPENSION METHODS FOR HEART— GASKBLL'S
HEART-LEVER AND CLAMP.

1. Gaskell's Heart-Lever (Suspension Methods).

(a.) This lever is extremely convenient (iig. 187). Expose the
heart of a pithed frog, ligature and divide the frsenum, tie a fine

silk thread to the apex of
the ventricle, and attach the
thread to the writing-lever
placed ahove it. The lever
is kept in position hy a thin
thread of elastic, which
raises the lever after the
contraction of the heart has
depressed it.

(b.) Record the movements
on a drum moving at a
slow rate. Record time in
seconds.

(r.) First the auricles con-
tract and pull down the
lever slightly, then the
greater contraction of the
ventricle pulls the lever
down further, and when the
Fig 187.— Showing the Arrangement of the Frog ventricle relaxes, the lever

and Lever for a Heart-Lever, supported by a . .,■,., , ; • .1 j

fine elastic thread. IS raised by the elastic thread.

Fig. 188 shows tracing ob-
tained when the heart is free and no clamp is applied.

Fig. ifi

-Tracing of a Frog's Heart taken with Apparatus shown in Fig. 187.
H. Heart-tracing ; T. Time in seconds.

A weak spiral spring may be used instead of the elastic thread.

LIV.]

SUSPENSION METHODS FOR HEART.

267

By this method, also, the effect of heat, cold, drugs on the heart
can be ascertained.

N.B. — If it is desired to ascertain the action of a drug on the
heart by this method, then make a snip in the heart so that the
blood may flow out and the drug act directly on the cardiac
muscle.

2. Varying Speed of Cylinder and Effect of Temperature.

(a.) By means of Gaskell's lever record the form of the heart-
beat witli varying rates of speed, marking time in seconds in each
case (fig. 189).

Fig. 189. — Shows how Heart Curve varies witn
rate of Drum. In i, 2, 3, r=time in seconds.
Gaskell's Lever.

Fig. 190. — Shows the effect of Normal Saline
directly applied to the Heart (at 0°, 15'
and 30° C.)- T time in seconds. Gaskell's
Lever.

(f).) Then ascertain effect of temperature on the rate of beat and
form of heart curve by applying normal saline, say at o°, 15°, and
30° C, directly to the heart (fig. 190).

3. Gaskell's Clamp.

(a.) On a suitable support arrange two recording long light
levers of the same length, and with their writing points exactly in
the same vertical line, recording on a slow-moving drum, the levers
being about 1 2 cm. apart. About midway between the two place

268

PRACTICAL PHYSIOLOGY.

[liv.

a Gaskell's clamp (fig. 191, C), fixed in an adjustable arm attached
to the same stand. To support the upper lever, fix to it a fine
thread of caoutchouc (E), and attach the latter to a slit or other
arrangement on the top of the support. The clamp consists of two

fine narrow strips of brass,
like the points of a fine pair
of forceps, which can be
approximated by means of a
screw.

(Ik) Expose the heart of a
pithed frog. Tie a fine silk
thread to the apex of the
ventricle, and another to the
upper part of the auricles, and
excise the heart. Tie the
auricular thread to the upper
lever and the ventricular one
at a suitable distance to the
lower lever,

(c.) Adjust the clamp (fig.
191, C) so as to clamp the
heart in the auricnlo-ventricu-
lar groove, but at first take care not to tighten it too much, or
merely just as much as will support the heart in position. After
fixing the heart by means of the clamp, fix the two levers so
that both are horizontal, and adjust the caoutchouc thread attached

Fia. 191. — Gaskell's Clamp. C. Heart in clamp ;
A. Aurkular, and V. Ventricular lever ; B.
Elastic to raise A after it is pulled down.

/^JOUUIAAJUUUIAJUUUUUUUUUUU

UUUUUUUl

Fig.

-Tracing from Auricle (A) and Ventricle (r)by Gaskell's Method.
T. Time in seconds.

to the upper one, so that it just supports the upper lever, and when
its elasticity is called into play by the contracting auricles pulling
down the lever, it will, when the auricles relax, raise it to the
horizontal position again.

(d.) Adjust a time-marker to write exactly under the writing

LIV.]

SUSPENSION METHODS FOR HEART.

269

points of the two levers. Moisten the heart from time to time
with serum or dihite blood.

{e.) After obtaining a tracing where the auricle and ventricle
contract alternately (tig. 192), screw up the clamp slightly until
the ratio of auricular to ventricular contraction alters, i.e., until,
by compressing the auriculo-venti-rcular groove, the impiilse from
the auricles to the ventricle is " blocked " to a greater or less
extent, when the auricles will contract more frequently than the
ventricle.

4. Excised Heart (Gotch's Arrangement).

By this method all the parts are fixed to a y-piece which is
clamped in a stand, so that the whole, preparation, electrodes and
everything, can be easily adjusted (fig. 193).

Fia. 193.— Gotch's Arrangement for Excised Heart. All parts are fixed on one T-p'ece,
T.P. P. Clanip-forceps for heart ; C. Cork ; L. Lever.

(a.) Excise a frog's heart, suspend it by clamp-forceps (F) to a
horizontal rod attached to a y-piece (T.P.). On the "p-piece is
a cork into which the electrodes are fixed, while the heart pulls on
a counterpoised lever.

{h.) By means of this arrangement we can (i) with a Stannius
heart show (i.) the latent period of cardiac muscle or cardiac delay,
(ii.) the delay of transmission of an impulse from auricle to
ventricle in the groove ; (2) Avith a beating heart, the refractory
period, rhythm, inhibition from the sinus (crescent), effect of
atropine, muscarine, &c.

5. Place a frog on a crank-myograph, attach the apex of the
heart still in situ to the crank-lever and record its movements.

270 PRACTICAL PHYSIOLOGY. [LV.

6. Writing Point of Bayliss. — When it is necessary to diminish
friction as much as possible, this style is most excellent. Fix to a
straw a piece of gummed paper, and to this attach a bit of peritoneal
membrane (same as is used for oncometers) and a bit of capillary
glass tube fused to a little ball at the end, and attached to the
peritoneal membrane by Front's glue. The membrane is made
broad to give rigidity in the direction of movement of the lever.

7. Put a glass tube in the oesophagus and leave the heart attached.
Pass water at different temperatures through the tube and observe its etTect
on the heart.

(Engelmann, " Versuche am suspendirten Herzen, " PJluger^s Archiv., lii.
Ivi., lix. ; Kaiser, Zeits.f. Biol., xxxii., 1895.)

LESSON LV.

STANNIUS'S EXPERIMENT— INHIBITION— LATENT
PERIOD OP HEART-MUSCLE.

1. Stannius's Experiment. — Pith a frog, and expose its heart.

(a.) With a seeker clear the two aortas from the auricles, and with
an aneurism needle pass a moist silk thread between the two aortae
and the superior venae cavae ; turn up the apex of the heart, divide
the fraenum, and raise the whole heart to expose its posterior
surface, and the crescent or line of junction of the sinus venosus
and the right auricle. Bring the two ends of the ligature round
the heart — call this for convenience No. i ligature — tie them, and
tighten the ligature just over the " crescent," so as to constrict the
line of junction of the sinus venosus with the right auricle. Before
tightening the ligature, observe that the heart is beating freely.
On tightening the ligature, the auricles and ventricle cease to beat,
and remain in a state of relaxation, while the sinus venosus con-
tinues to beat at the same rate as before. After a time, if left to
itself, the ventricle may begin to beat, but with an altered rhythm.
If the relaxed ventricle be pricked, it executes a single contraction,
i.e., a single stimulation produces a single contraction.

(h.) When the heart is still relaxed, take a second ligature (No.
2), and preferably of a different colour, to distinguish it from No.
I ; place it round the heart, and tighten it over the auriculo-ven-
tricular groove, so as to separate the ventricle from the auricles.
Immediately the ventricle begins to beat again, while the auricles
remain relaxed or in diastole.

LV.] STANNIUS'S EXPERIMENT. 27 1

(<",) Instead of applying No. 2 ligature, the ventricle may be cut
off from the auricles by means of a pair of scissors. Immediately
after it is amputated, the ventricle begins to beat. Stannius hga-
ture is of practical importance (i.) for arresting the uninjured
ventricle to measure its electro-motivity (Lesson XLVI.), (ii.) for
ascertaining the latent period of cardiac muscle (p. 272) (Hofmann,
" Function d. Scheidewandnerven d. Froschherzens," Pjlwjer's
Archiv., Bd. 60, p. 139).

2. Staii'case Character of the Heart-Beats.

Stannius a heart as above, i.e., arrest the beating of the auricles
and ventricle by tightening a ligature over the sino-auricular groove.
Attach the apex of the heart by means of a silk thread to a record-
ing lever, as in fig. 187. and record on a slow-moving drum.

The heart is quiescent. Stimulate it with a single induction
shock at intervals of 5 seconds. Notice that the first beat is
lower than the second, the second than the third, so that each beat
exceeds its predecessor in amplitude until a maximum beat is
obtained. The amount of increase gradually decreases towards the
end of the series. This is the " Staircase " of Bowditch.

3. Intracardiac Inhibitory Centre.

(a.) Expose the heart in a pithed frog, tie a fine silk ligature
round the frsenum, and divide the latter between the ligatured
spot and the pericardium. Gently raise the whole heart upwards
to expose the somewhat whitish V-shaped " crescent " between the
sinus venosus and the right auricle.

(J).) Arrange previously an induction coil for repeated shocks.
Place the electrodes — which must be fine, and their points not too
far apart (2 millimetres) — upon the crescent, and faradise it for a
second ; if the current be sufficiently strong, after a period of delay,
the auricles and ventricle cease to beat for a time, but they begin
to beat even in spite of continued stimulation. The electrodes are
conveniently supported on a short cylinder of lead. They can be
fixed to the lead by modeller's wax.

(c.) Stimulate the auricles ; there is no inhibition or arrest.

{(l.) Apply a drop of sulphate of atropine solution (Lesson LVIL,
1) to the heart. Stimulation of the crescent no longer arrests the
heart. The atropine paral^^ses the inhibitory fibres of the vagus.

4. Inhibitory (Crescent) Arrest Recorded,

(a.) Take a tracing Avith Gaskell's lever. Stimulate the crescent
for 1-2 seconds with induction shocks as in 3, and observe the
arrest of the heart's beat (fig. 194). In the primary circuit place

272 PRACTICAL PHYSIOLOGY. [LV.

a small electro-magnetic signal. This will begin to vibrate when
the primary circuit is closed, and mark the period of stimulation as
a white patch on the black surface. Make its point record exactly
under the heart-lever. Take a time-tracing in seconds.

(6.) After a pause the beat begins, the contraction travelling
as a wave from sinus, through auricles to ventricle.

(c.) Stimulate the auricles. During inhibition the sinus beats,
but the auricles and ventricle do not, because the excitabiUty of the
auricles is so lowered that they do not propagate the excitatory
process.

(d.) Stimulate the ventricle mechanically, the heart beats in the
reverse order from ventricle, auricles to sinus.

Fia. iq4. — Arrest of the Frog's Heart-Beat by Electrical Stimulation erf the Crescent.
Sec. Time in seconds ; H. Heart-beats ; S. Stimulation.

5. Seat of the Motor Centres.

(a.) Expose a pithed frog's heart, cut out the ventricle with the auricles
attached to it, and observe that the heart continues to beat. Divide the
ventricle vertically by two parallel cuts into three portions. The middle
portion contains the auricular se])tuni, in which lie ganglionic cells. It con-
tinues to beat while the right and left lateral parts do not beat spontaneously,
but respond by means of a single contraction if they are stimulated.

6. Latent Period of Cardiac Muscle (Cardiac Delay). — This is

ascertained in the same way as in a skeletal muscle, but there is this
difference, the heart beats rhythmically while the skeletal muscle
is at rest until excited. Therefore the heart-beat must be brought
to a standstill. This can be done by a Stannius hgature.

{a.) Arrange an induction coil to give single shocks, putting in
the primary coil an electro-magnet which records its movement on
a slow-revolving drum. This will indicate the moment of stimu-
lation.

(h.) Expose the heart in a pithed frog, " Stannius " its heart
(Lesson LV.). This will arrest its beat. Then tie a silk thread to
the apex of the ventricle, and attach the thread to a Gaskell's heart-
lever. Arrange the heart-lever so that it records on a drum exactly
above the electro-magnet.

LVI.] CARDIAC VAGUS OF THE FROG. 273

((?.) Adjust a lever marking time in seconds exactly over the
electro-magnet lever.

{(f.) There will be recorded two horizontal lines ; stimulate with
a single induction shock, — the moment of stimulation will be
indicated by the second lever, and shortly after, the heart will

Fig 195.— Tracing of Stanniused Heart of Frog, stimulated at 5 with a single Maximum
Induction Shocli. T. Time in seconds. Gaslcell's Lever.

respond ; the interval represents the " latent period " — which may
be about half a second according to temperature and other (con-
ditions (fig. 195).

(e.) Stimulate the auricle and observe the longer " delay " ; the
wave of contraction takes longer to travel, and is delayed at the
groove.

LESSON LVI.

CARDIAC VAGUS AND SYMPATHETIC OP THE
FROG AND THEIR STIMULATION.

1, Cardiac Vagus of the Frog — To Expose it. — ]\Iake a pre-
liminary dissection before attempting to stimulate the vagus.

Pith a frog, or destroy its brain and curarise it. Lay it on
its back on a frog-plate. Expose the heart, remove the sternum
and pull the fore-U'gs well apart. Introduce a small test-tube or
stick of sealing-wax into the oesophagus to distend it ; the nerves
leaving the cranium are better seen winding round from behind
when the oesophagus is distended. Remove the muscles covering
the petrohyoid muscles, wliieli reach from the petrous bone to the
posterior horn of tlie hyoid bone (tig. 196). Three nerves are seen
coursing roiuid the pharynx parallel to these muscles. The lowest
is the hypoglossal (Hg), easily recognised by tracing it forward to

8

274

PRACTICAL PHYSIOLOGY.

[lvi.

tlie tongue, above it is the vagus in close relation with a blood-
vessel (V), and still further forward is the glosso-pharyngeal (GP).
Observe the laryngeal branch of the vagus (L). The vagus, as
exposed outside tlie cranium, is the vago-sympathetic. The
glosso-pharyngeal and vagus leave the cranium through the same
foramen in the ex-occipital bone, and tlirough the same foramen
tlie sympathetic enters the skull.

2. Stimulation of the Cardiac Vagus.

(a.) Adjust a Gaskell's heart-lever to record the contractions of
the heart on a revolving drum moving at a slow rate.

HB

PK

Fia. 196. — ScLeme of the Dissection of the Frog's Vagus. SM. Siibmentalis ; LULnng;
V. Vagus; 6'P. Glossopharyngeal ; Ug. Hypoglossal; L. Laryngeal; PH, SU, GH,
on. Petro-, Sterno-, Genio-, Omo-hyoid ; HB. Hyoid ; HG. Hyoglossus ; H. Heart;
BR. Brachial plexus.

(h.) Place well-insulated electrodes under the trunk of the vagus.
Take a normal tracing, and then stimulate the vagus with an inter-
rupted current, and observe that the whole of the heart is arrested
in diastole. The best form of electrodes is the fine shielded elec-
trodes shown in fig. 227. Although the faradisation is continued,
the heart recommences beating. The arrest, or period of inltibi-
tion, is manifest in the curve by the lever recording merely a
.=*traight line. If the laryngeal muscles contract, and thereby afif'ect

LVI.] CARDIAC VAGUS OF THE FROG. 275

the position of the heart, divide the laryngeal branches of the
vagus.

(c.) Note that when the heart begins to lieat again, the beats are
small at first and gradually rise to normal. In some instances,
however, they are more vigorous and quicker (fig. 197).

3. Latent Period or Delay of Vagus. — For this purpose a time-
marker and an arrangement to indicate when the stimulus is thrown
into the nerve are required.

(a.) Arrange the heart-lever as before, and adjust a time-marker
to write exactly under the heart-lever,

{Ik) Arrange an induction coil for repeated shocks, and keep
Neef's hammer vibrating. Into the secondary circuit introduce an
electro-magnet with a writing-lever attached to it ; so adjust the
electro-magnet that its writing-style writes exactly under the heart-
lever, anil arrange that when the writing-style on the electro-magnet

I !

; ; Heart Beat.

1 1 1 I I I I I I I 1 1 I I I I I I ' I I I I I I I I 1 1 I I 1 I I I I I -

Stimulation

Fig. 197.— Vagus Curve of Frog's Heart.

is depressed — e.r/., by means of a weight — the secondary circuit is
short-circuited, so thatno stimulus is sent along the electrodes under
the trunk of the vagus.

(r.) When all is ready, lift the weight olf the electro-magnet,
whereby the secondary current is un-short-circuited, the electro-
magnet lever rises up, records its movements on the cylinder, and
at the same moment the induction shocks are sent through the
v.igus. Observe that the heart is not arrested immediately, but a
certain time elapses — the latent j)eriod — usually about one beat of
the heart (i*5 sec), before the heart is arrested.

{d.) Short-circuit the secondary current again, and observe how
the heart gradually resumes its usual rhythm — sinus venosus,
auricles, and ventricle.

{i\) Repeat {c.) several times, noting that the heart after arrest
goes on beating in spite of continued stimulation,

(J.) An electro-magnet may be introduced into the primary
circuit to mark the moment of stimulation just as in Lesson LIV. 6.

4. Action of the Sympathetic on the Heart of the Frog.

{a.) Pith a frog, or preferably a toad, cut away the lower jaw, and continue
the slit from the augle ot the mouth downwards for a short distance. Turn

276

PRACTICAL PHYSIOLOGY.

[lvi.

the parts well aside, and expose the vertebral column where it joins the skull.
Remove the mucous membrane covering the roof of the moutli. The sym-
pathetic is found before it joins the vagus emerging from the cranium (fig.
198). Carefully isolate tlie sympathetic. It lies immediately under the
levator anguli scapuls, which must be carefully removed with fine forceps,
when the nerve comes into view, usually lying under an artery. The nerve
is usually pigmented. Put a ligature round it as far away from the skull as
practicable, and cut the nerve below the ligature.

Fig. 198.— Scheme of the Frog's Sympathetic. LAS. Levator anguli scapulae; Sytn.
Sympathetic ; GP. Glosso-pharyngeal ; VS. Vago-sympathetic ; O. Ganglion of the
vagus; Ao. Aorta; SA. Subclavian artery (Gaskell).

{b.) Expose the heart and attach its apex to a lever supported by an elastic
thread as in Gaskell's method. Record several contractions, and then stimu-
late the sympathetic with weak interrupted shocks by means of fine electrodes.
The heart beats quicker. If the heart is beating quickly, reduce the
number of beats by cooling it with ice.

(c.) If desired, the vagus may be isolated and stimulated, and the effects of
the two nerves compared (altliough the vagus outside the skull is really the
vago-sympathetic).

Stimulation of the intracranial vagus— ?.c., before it is joined by the
sympathetic — is somewhat too ditiicult for the average student, and is there-
fore omitted here.

A'./A — It is imj)ortant to note that the effect of vagus stimulation on the
heart varies with the season of the year, and is often different in the two vagi.
In some animals one vagus is inactive.

LVll.] DRUGS AND CURRENT ON HEART. 277

LESSOX LVII.

DRUGS AND CONSTANT CURRENT ON HEART
—DESTRUCTION OF CENTRAL NERVOUS
SYSTEM.

1. Action of Drugs on the Heart — Muscarine, Atropine, and
Nicotine. — Eitlier the excised heart, placed in a watch-glass, or the
heart m sitn may be used, or Gotch's method may be employed
()) 269). The heart may be attached to a Gaskell's lever (fig. 187)
and the result recorded. The last is the best plan, for by this moans
a tracing can readily be obtained.

(a.) Muscarine. — Pith a frog, expo.se its heart, and if desired
attach its apex to a Gaskell's lever recording its movements. Kecord
the result (fig. 199). To get the full effect of the drug on cardiac
action snip the heart to allow the blood to run out. With a fine
pipette apply a few drops of serum or normal saline (0.6 p.c.) con-
taining a trace of muscarine, which rapidly arrests the rhythmical
action of the heart, the ventricle being relaxed — i.e., in diastole —
and— if uncut — distended with blood. Before it stands still the
heart-beats become less and less vigorous. (This is a good method
of collecting a considerable quantity of frog's blood when it is
wanted for any purpose from the heart.)

(h.) When the ventricle is completely relaxed in the diastolic
phase, it is very inexcitable, responding only to strong stimuU, and
perl laps the auricles not at all.

Atropine. — To the heart arrested with muscarine,

(c.) After a few minutes, with another pipette apply a few drops
of a 0.5 per cent, .solution of sulphate of atropia iii normal saline.
The heart gradually' again begins to beat rhythmically. Thus the
atropine undoes the effect of the muscarine. This is sometimes
spoken of as " Antagonistic action" of drugs (fig. 199).

{(I.) Faradise the crescent or inhibitory centre of the atropinised
heart ; the heart is no longer arrested, becaxise the atropine has
paralysed the intracardiac inhibitory mechanism.

(1?.) Pilocarpine. — In another frog, arrest the action of the heart
with pilocarpine, and then a])ply atropine to antagonise it, observing
that the heart beats again after the action of atropine.

(/'.) Nicotine. — Apply nicotine (.2 milligram). Stimidation of
the vagus no longer arrests the heart's action, but stimulation of the
sinus venosus does ; so that nicotine paralyses the fibres of the
vagus, and leaves the intracardiac inhibitory mechanism intact.

278

PRACTICAL PHYSIOLOGY.

[lvii.

2. Constant Current on the Heart.

(a.) Pith a frog. Cut out the heart, dividing it below the
auriculo- ventricular groove, thus obtaining an " apex " preparation
which does not beat spontaneously.

Fig. 199. — Tracing of Heart attached to Gaskell's Lever, arrested by Muscarine, and
Rhythm restored by Atropine. M. Muscarine effect ; A. Atropine applied ; T. Time
in seconds.

(h.) By means of sealing-wax, fix a cork to a lead base 5 cm.
square, cover the upper end of the cork with seahng-wax, and
thrust through it two wires to serve as electrodes, about 4 mm,
apart (fig. 200), or by means of sealing-wax fix two fine wires upon
an ordinary microscopic glass slide to act as electrodes. Cover the
whole with a beaker lined with moist blotting-paper. Place the
heart apex with its base against one electrode, and its apex against
the other.

Fig. 200— Support for Frog's Heart.
E. Electrodes ; U. Heart.

Fig. 201. — Staircase Character
of Heart-Beat.

(c.) Arrange two Daniell's cells in circuit, connect them with
a key, and to the latter attach the electrodes. Pass a continuous
current in the direction of the apex. The heart resumes its
rhythmical beating, and continues to do so as long as the constant
current passes through the living preparation.

3. The Staircase.

(a.) To a microscopical glass slide (3x1) fix witli sealing-wax two copper
wires in the long axis of the slide, their fi'ee ends being about 3 millimetres

LVIII.] PERFUSION OF FLUIDS. 2/9

apart. They will act as electrodes. Connect the other ends of the wires to
a Du Bois key introduced into the secondary circuit of an induction machine.
Arrange the primary coil for single induction shocks, introducing a Morse
key in the circuit.

(b,) Make an "apex jtreparation," and jilace it on the electrodes on the
glass slide. Rest on the heart a heart-lever jiroperly balanced and arranged
to record its movements on a slow-moving drum (5 mm. per second). The
prei)aration does not contract spontaneously, but responds to mechanical or
electrical stimulation.

(c.) Stimulate the apex preparation with single break induction shocks at
intervals of about ten seconds. To do this, un-short-cii'cuit the sucondnry
circuit, depress the Morse key, short-circuit the secondary circuit, and close
the Morse key again. Repeat this at intervals of ten seconds, and note that
the amplitude of the second contraction is greater than the first, that of
the third than the second, the fourth than the third, and then the successive
beats have the same am])litude (fig. 201). Allow the heart apex to rest for a
few minutes, and repeat the stimulation. Always the same result is obtained.
From the graduated rise of the first three or four beats after a period of rest,
the phenomenon is known as the "staircase." The increment is not equal
in each successive beat, but diminishes from the beginning to the end of the
series.

{(l.) If, while the apex is relaxing, it be stimulated by a closing shock, it
contracts again, so that the lever does not immediately come to the abscissa.

(«. ) II the Morse key be rapidly tapped to interrupt the primary current,
the contractions become more or less fused, and the lever remains above the
abscissa writing a sinuous line.

4. Effect of Destruction of the Nervous System on the Heart and Vas-
cular Toniis.

{a.) Destroy the brain of a frog, and expose its heart in the usual wa}^,
taking care to lose no blood ; note how red and full the heart is with blood.

(b.) Suspend the frog, or leave it on its back, introduce a stout {)in into the
spinal canal, destroy the spinal cord, and leave the pin in the canal to prevent
bleeding. Observe that the heart still continues to beat, but it is p((le and
collapsed, and apparently empty ; it no longer fills with blood. The blood
remains in the greatly dilated abdominal blood-vessels, and does not return
to the arterial system, so that the heart remains without blood. It the belly
be opened, the abdominal veins are seen to be filled with blood.

(c. ) Amputate one limb, perhaps not more than one or two drops of blood
will be shed, while in a frog with its spinal cord still intact, blood flows freely
after amputation of a limb.

LE8S0X LYIIT.

PERFUSION OP FLUIDS THROUGH THE HEART
—PISTON-RECORDER.

1. Perfusion of Fluids through the Heart.
The Fluid. — (a.) Take two volumes of normal saline, add one
volume of defibrinated sheep's blood, mix, and filter. See that

28o

PRACTICAL PHYSIOLOGY.

[lviil

the blood is thoroughly shaken up with air before mixiBg it. This
is the best fluid to use.

{/).) Ringer's Fluid. — Take 99 cc. of .6 per cent, NaCl solution,
saturate it with calcic phosphate, and add I cc. of a i per cent,
solution of potassic chloride.

(c. ) Rub up in a mortar 4 grams of dried ox-blood (this can be purchased)
with 60 cc. of normal saline. Allow it to stand some time, add 40 cc. of
water, and filter.

2. Preparation of the Heart.

('I.) Pith a frog, expose its heart, ligature and divide the fraenum
beliind the ligature.

{/i.) Take a two-wayed cannula (fig. 202), attach india-rubber

tubing to each tube, and fill the tubes and cannulse with the

fluid to be perfused. Pinch the india-rubber

tubes with fine bull- dog forceps to prevent the

escape of the fluid.

{(■.) Tie a fine thread to the apex of the
ventricle. To this thread a Avriting-lever is to
be attached.

(d.) By means of the fraenum ligature raise
the heart, with a pair of scissors make a cut
into the sinus, and through the opening intro-
duce the double cannula passed through a
cork, until its end is well within the ventricle.
Tie it in with a ligature, the ligature constrict-
ing the auricles above the auriculo- ventricular
groove, thus making what is known as a
" heart-preparation." Cut out the heart with
its cannula.
(e.) In a filter-stand arrange a glass funnel, with an india-rubber
tube attached, at a convenient height (6-7 inches above the heart),
fill it with the perfusion fluid, clamp the tube. Attach this tube
to one of the tubes — the inflow — connected with one stem of the
cannula, taking care that no air-bubbles enter the tube. Adjust
the height of the reservoir so that the fluid can flow freely through
t)ie heart, and pass out by the other tube of the cannula. Place a
vessel to receive the outflow fluid. After a short time the heart
will begin to beat.

(/.) Place the heart in a cylindrical glass tube, fixed on a stand,
and arranged so that the cork in which the cannula is fixed fits
into the mouth of the tube. A short test-tube does perfectly
well. The lower end of the glass tube has a small aperture in it
through which the thread (c) is passed, and attached to a writing-
lever arranged on the same stand as the glass vessel. See that

Fig. 202. — Kronecker's
Cauiiula for Frog's
Heart.

LIX.] ENDOCARDIAL PRESSURE. 28 1

the lever is horizontal, and writes freely on a slow-moving recording
drum. - Every time the heart contracts it raises the lever, and during
diastole the lever falls (fig. 203).

In this way it is possible to use various fluids for perfusion. The
fluids may be placed in separate reservoirs, each communicating
M'ith the inlet tube, and
capable of being .shut oft" or
opened ])y clamps as re-
quired. Further, liy poison-
ing the supply fluid Avith
atropine, muscarine, sparte-
ine, or other drug, one can
readily a.scertain the eff"ect
of these drug8 on the heart,
or the anta<'onism of one . , , „ . ., .

1 , ., Fig. 203. -Tracing obtainea from a Frogs lleart,

drug to another. throuch which Dilute Blood was perfused. The

Instead of a glass funnel c.a.tn'lctinu' heart raised a registering lever.

J^ . . The lower line indicates seconds.

as a reservoir for the fluid,

one may use a ^Marriotte's flask (fig. 204), the advantage being that
the pre.ssure of the fluid in the inflow tube is constant. Another
simple arrangement is to have a bird's water-bottle, with a curved
tube leading from it to the inflow tube of the cannula.

3. Piston-Eecorder (of Schafer).

The heart is tied to a two-way cannula as before, and is intro-
duced into a horizontal tube with a dilatation on it. The tube of
the recorder is filled with oil, and as the heart dilates it forces the
oil along the tube and moves a light piston resting on it. When
systole takes place, the oil recedes, and with it the piston. The
piston records on a slow-moving drum placed horizontally and
gives excellent results.

LESSON LIX.

ENDOCARDIAL PRESSURE— APEX PREPARATION
—TONOMETER.

1. Endocardial Pressure in the Heart of a Frog.

(a.) Proceed as in tlie previous exjieriment (a.), [h.) (omit c), {d.).

(b.) Arrange a hog's nu'iuiuy manometer provided with a writing-style as
in fig. 204. Attach tlie inlet tube of the cannula to the Marriotte's flasks
(a, b). and connect the outllow with the tube of the mercury manometer. It
is well to have a y-tube between the heart and the manometer, but in the
heart apparatus, as shown and used, the exit tube is preferable. See that

282

PRACTICAL PHYSIOLOGY.

[LIX.

no air-bubbles are present in the system. Every time the heart contracts
the mercury is displaced and the writing style is raised, and records its move-
ments on a slow-moving drum.

(r. ) Take a tracing with the outflow tube and Mariiotte's flask shut off, so
that the whole effect of the contraction of the heart is exerted upon the
mercury in the manometer. Take another tracing when the fluid is allowed
to flow continuously through the heart. The second Marriotte's flask shown
in the figure is for the perfusion of fluid of a different nature, and by means
of the stopcock (s) one can pass eitlier the one fluid or the other through the
heart. The little cup (d) under the heart can be raised or lowered, and filled
with the nutrient fluid, and in it the heart is bathed.

2. Apex Preparation. — In this pre-
paration of the heart only the a})ex
of the heart is used. As a rule, it
does not beat spontaneously until
suflficient pressure is applied to its
inner surface by the fluid circulating
through the heart.

(«.) Proceed as in Lesson LVIII. 2
(«.), (b.) (omit c), {d.), with this
difference, that in (rf.) the cannula
is placed deeper into the ventricle,
and the ligature is tied round the
ventricle below the auriculo-ventricu-
lar groove. Excise the heart and
cannula, and attach it to the heart
apparatus as in the previous experi-
ment.

(b.) If the "heart aj)ex" prepara-
tion does not contract spontaneous!}',
stimulate it by, e.g., single induction
shocks, either make or break. To
this end adjust an induction machine,
the wires from the secondary coil being
attached, one to the cannula itself,
while the other is placed in the fluid

in the glass cup, into which the heart is lowered.

(c.) By introducing an electro-magnet with a recording lever into the

primary circuit, and having a time-marker recording at the same time, one

can determine the latent period of the apex preparation. It is about 0.15

sec.
(d.) If desired, the effect of a constant current may be studied in this way

instead of by the method described in Lesson LVI. 2, The apex beats

rhythmically under the influence of the constant current.

3. Roy's Frog-Heart Apparatus or Tonometer. — This apparatus registers
the change of volume of the contracting heart. Fig. 205 shows a scheme of
the apparatus, and fig. 206 the apparatus itseli. The apparatus consists of a
small bell-jar, resting on a circular brass plate about 2 inches in diameter,
and fixed to a stand adjustable on an u])right. In the biass plate are two
openings, the small one leads into an outlet tube (e), provided with a stop-
cock. The other is in the centre of the plate, and leads into a short cylinder
I cm. in length by i cm. in internal diameter. A groove runs round the out-
side of this cylinder near its lower edge, to permit of a membrane being tied

Fig. 204. — Sulienie of Kronecker's Frog
Manometer.

LIX.]

ENDOCARDIAL PRESSURE.

283

on to it. lu this cylinder works a light aluniinium piston '/)), slightly less in
diameter than the cylinder. Around the lower aperture of the cylinder is tied
a piece of flexible animal membrane, the liga-
ture resting in the grooved collar. The iree
part of the membrane is tied to the piston, from
the centre of whose under-surface (p) a needle
passes down to be attached to a light writing-
luver (/) fixed below the stage. The bell-jar is
filled with oil (0), while in its uj)per opening is
fitted a short glass stopper, perforated to allow
the passage of a two-waved heart-cannula with
the heart attached (h). In using the instrument
proceed as follows : —

(a.) Fix the bell-jar to the circular brass
plate by the aid of a little stiff grease. Tie a
piece of the delicate transparent membrane —
such as is used by perlumers for covering the
corks of bottles — in the form of a tube round
the lower end of the
grooved cylinder ;
atterwards the lower
^__ end of the membrane
IS fixed to the ]iis-
ton, taking care that
the needle attached to the piston hangs towards the recording lever. Drop
iu a little glycerin to moisten the membrane.

Fig. 205.— Scheme of Roy's Tonometer.

FlO. 2o6. — Key's Tonometer, as made by the Cambridge Scientific
Instrument Company.

(b.) Fill the jar with olive-oil, and have the recording apparatus ready
adjusted. Prepare the heart of a large frog [Lesson LVIIL (a.), {i.) (.omit c),

284 PRACTICAL PHYSIOLOGY. [LX.

('/.'>]. the cannula used being one fixed in the glass sto])per of the bell-jar, and
attach the inlet tube of the cannula to the reservoir of nutrient fluid, while
the outlet tube is arranged so as to allow fluid which has passed through the
lieart to drop into a suitable vessel.

(*;. ) Introduce the cannula, with the heart attached, into the oil, and see
that the stopper is securely fixed. Open the stopcock (c), and allow some oil
to flow out of 0, thus rendering tlie pressure within sub-atmospheric ; and as
soon as the pressure has fallen sufficiently, and the little piston is gradually
drawn up to the proper height, close the stopcock, attach the needle of the
piston to the recording light lever, and take a tracing.

LESSON LX.

HEART-VALVES— ILLUMINATED HEART— STETHO-
SCOPE —CARDIOGRAPH — POLYGRAPH — MEIO-
CARDIA — REFLEX INHIBITION OP THE
HEART.

1. Action of Heart-Valves. — This is of value in order that the
student may obtain a knowledge of the mechanical action of the
valves. The heart and lungs of a sheep —with the pericardium still
unopened — must he procured from the butcher.

(a.) Open the pericardium, observe its reflexion round the
blood-vessels at the base of the heart. Cut oif the lungs moderately
wide from the heart. Under a tap wash out any clots in the heart
by a stream of water entering through both auricles. Prepare from
a piece of glass tul;)ing, 15 mm. in diameter, a short tube, 8 cm. in
length, with a flange on one end of it, and another about 60 cm.
long. Fix a ring to hold a large funnel on a retort stand.

(h.) Tie the short tube into the superior vena cava, the flanged
end being inserted into the vessel. It must be tied in with well-
waxed stout twine. In the pulmonary artery (P.A.) — separated
from its connections with the aorta, M'hich lies behind it — tie the
long tube, the flange securing it completely. Ligature the inferior
vena cava, and the left azygos vein opening into the right auricle.
Connect the short tube by means of india-rubber tubing with the
reservoir or funnel in the retort stand. Keep the level of the
water in the funnel below the upper surface of the P.A. tube. Fill
the funnel with water ; it distends the right auricle, passes into
the right ventricle, and rises to the same height in the P.A. tube
as the level of the fluid in the funnel. Compress the right ventricle
with the hand ; the fluid rises in the P.A. tube ; and observe on
relaxing the pressure that the fluid remains stationary in the P.A.
tube as it is supported by the closed semilunar valves. If the right

LX.] HEART-VALVES. 285

ventricle be compressed rhythmically, the fluid will rise higher and
higher, until it is forced out at the top of the P.A. tube, and a
vessel must be lield to catch it. Observe that the column of fluid
is supported by the semilunar valves, and above the position of the
latter observe the three bulgings corresponding to the position of
the sinuses of Valsalva.

(r.) Repeat (/*.), if desired, on the left side, tying the long tube
into the aorta, and the short tube into a pulmonary vein, ligaturing
the others.

(il.) Cut away all the right auricle, hold the heart in the left
hand, and pour in water from a jug into the tricuspid orifice. The
water runs into the right ventricle, and floats up the three cusps of
the tricuspid valve ; notice how the three segments come into apposi-
tion, M-hile the upper surfaces of the valves themselves are nearly
horizontal.

(e.) With a pair of forceps tear out one of the three segments of
the semilunar valve of the P.A. Tie a short tube into the P. A.,
and to it attach an india rul)ber tube communicating with a funnel
supported on a retort stand. Pour water into the funnel, and
observe that it flows into the right ventricle, floats up, and securely
closes the tricuspid valve. The semilunar valves have been
rendered incompetent through the injury. Turn the heart any way
3'ou please, there is no escape of fluid tluougli the tricuspid valve.

(/.) Take a funnel devoid of its stem and with its lower orifice
surrounded by a flange, and tie it into the aorta. Cut out the aorta
and its semilunar valves, leaving a considerable amount of tissue
round about it. Place the funnel Avith the excised aorta in a filter
stand, and pour water into the funnel ; much of it will esca}je
through the coronary arteries ; ligature these. The semihuiar
valves are quite competent, i.e., they allow no fluid to escape
between their segments. Hold a hghted candle under the valves,
and observe through the water in the funnel how they come
together and close the orifice ; observe also the triradiate lines, and
the lunules in apposition projecting vertically.

('/.) Slit open the P. A., and observe the form and arrangement
of the semilunar valves.

[T.S. Ventricles. — Make a transverse section through both
ventricles, and compare the shape of the two cavities and the
relative tliickness of their respective M'alls.

Casts of Heart. — Study two casts of the heart-ventricles (by
Ludwig and Hesse), (i) in diastole, and (2) in systole.

Effect of Ligature. — Ligature any large vessel attached to the
heart ; one feels the sensation of something giving way when the
ligature is tightened. Cut away the ligature, open the blood-vessel,
and observe the rupture of the coats produced by the ligature.]

286

PRACTICAL PHYSIOLOGY.

[lx.

2. Illuminated Ox-Heart (Gad).

This must be arranged previously by the demonstrator. Two
brass tubes with glass windows are tied, one into the left auricle {d)
(7 cm. diameter) and the other {c) into the aorta (5 cm. diameter).
These are connected with a large reservoir (R), as shown in the
figure. The interior of the heart is illuminated by a small elec-
tric lamp (Z) pushed in through the apex of the heart, and served

by several small Grove cells.
Into the apex is tied a brass
tube, which is connected with
a large india-rubber bag with
thick walls (P). Fill the whole
with water. On compressing
the elastic bag, fluid is driven
onwards, when the play of
the valves can be beautifully
studied. On relaxation, the
mitral valves open and the
aortic valves clo.se.

After each demonstration,
remove the glass windows of
the cannulas and the caout-
chouc tubes, and preserve
the heart in 10 p.c. chloral
hydrate.

3. The Stethoscope —
Heart Sounds.

(a.) Place the patient or
fellow-student in a quiet
room, and let him stand
erect and expose his chest.
Feel for the cardiac impulse,
apply the small end of the
stethoscope over this spot, and apply the ear to the opposite end of
the instrument. The left hand may be placed over the carotid or
radial artery to feel the pulse in either of those arteries ; compare
the time-relations of the pulse with what is heard over the cardiac
impulse.

If).) Two sounds are heard — the first or systolic coincides with
the impulse, and is followed by the second or diastolic. After this
there is a pause, and the cycle again repeats itself. The first sound
is longer and deeper than the second, which is of shorter duration
and sharper.

(c.) Place the stethoscope over different parts of the praecordia,

Fig. 207.— Scheme of Gad's Apparatus to show
the play of the Valves of the Heart. A. L.
auricle ; d. Its wiiulow, and communicating
with 6, the inlet tube for water from the
reservoir, R\ V. L. ventricle, illuminated by
an electric lamp, I, and communicating with
the elastic bag, P ; e. Glass window fixed in
tube in aorta ; a. Tube carrying fluid to the
reservoir.

LX.]

HEART-VALVES.

287

noting that the first sound is lieard loudest at the apex beat, while
the second is heard loudest at the second right costal cartilage at
its junction with the sternum.

4. Cardiograph. — Several forms of this instrument are in use,
including those of Marey, B. Sanderson, and the pansphygmograph
of Brondgeest. Use any of them.

(a.) Place the patient on his back with his head supported on a
pillow. Feel for the cardiac impulse between the fifth and sixtli
ribs on the left side, and about half an inch inside the mammai y
line.

{/).) Arrange the cardiograph by connecting it (fig. 208) witli
thick- walled india-rubber tubing to a recording Marey 's tambour
adjusted to write on a drum (fig.
150). It is Avell to have a valve
or a y-tube capable of being
opened and closed between the
receiving and recording tambours,
in order to allow air to escape if
the pressure be too great.

(c.) Adjust the ivory knob of
the cardiograph (;;) over the car-
diac impulse where it is felt most,
and take a tracing. Fix, varnish,
and study the tracing or cardio-
gram. P

Fia. 208.— Marey's Cardiograph, p. Button
5 Effect of SwallOwinff on the P'-'^^'^d over cardiac impulse : « Screw

° to regulate the projection of p ; t.

Heart-Beats (Man). Tube to other tambour.

AVith a watch in front of you,
count the number of your own pulse-beats per minute, and then
slowly sip a glass of water, still keeping your finger on the pulse.
Count the increase in the number of pulse-beats during the
successive acts of swallowing. This is due to the inhibitory action
of the vagus being set aside.

6. Reflex Inhibition of the Heart (Rabbit).

Place one hand over the chest of a rabbit and feel the beating of
tlie heart. With the other hand suddenly close its nostrils, or
bring a little ammonia near the nostrils, so as to cause the animal
to close them. Almost at once the heart is felt to cease beating
for a time, but it goes on again.

7. Goltz's Tapping Experiment (Frog).

(a.) Destroy the cerebrum and optic lobes of a frog. Pin it out on a fi"og-
plate, and expose its heart, or attach the heart to a Gaskell's lever. Expose

288

PRACTICAL PHYSIOLOGY.

[lx.

the intestines and tap them sevcal times with the handle of a scalpel. The
heart ceases to beat lor a ti'ue, being arrested reflexly. The afferent nerve
is the sympathetic horn t*ie abdomen, and the efferent the vagus. The

tapping succeeds more promptly if the intestines are slightly inflamed by
exposure to the air.

(b.) It suflBces to exert digital pressure over the abdomen to produce tliis
reflex arrest of the heart.

LX.]

HEART-VALVES.

289

ADDITIONAL EXERCISES.

8. Polygraph ot Knoll and Rotlie. — This is a most convenient apparatus,
both lor work in the laboratory and at the bedsiiie. Moreover, it is so
arranged that two tracings can be taken simultaneously. It is made by
H. Rothe, Weiizelbad, I'lague. It can be used to take simultaneously

Fig. 210. — /y. Tiaoiiii; nf the cardiac iniijuUe. the resiMratory iiioveincnts of the chest
no: being arrested.

cardiac impulse and a pulse tracing, or respiratory movements and a pulse
tracing, or two j)u]se tracings.

Fig. 209 shows the arrangement of the apparatus. It consists of a drum
(F) moved by clockwork within the box D. K is a catch for setting D in

Fio. 211.— Showing the Method of Fixing thfi Receiving Tambour of Rothe's
Polygraph on an Artery.

motion. M is a time-marker beating seconds. H, H are two Marey's
registering tambours adjustable on the stand C. B is a tambour which can
be fixed over an artery or over the cardiac impulse, while A is a bottle-shaped
caoutchouc bag whicli can be strapped to the body for studying the respiratory
movements.

290

PRACTICAL PHYSIOLOGY.

[lx.

(a.) Adjust the tambour (B) over the cardiac impulse, and fix the bag (A)
on the abdomen so as to record simultaneously the cardiac impulse and the
respirations (fig. 210). The experimenter may also take a tracing of the
cardiac impulse while the respiration is arrested.

j^:jLj:.M-^kK>u

!0-^x-lu

Fig. 212.- />. Tracing of radial pulse; /.'. Eespirations ; T. Time in feconds.

{h.) Take a tracing of the radial pulse and the respiratory movements.
Fig. 211 shows how the receiving tambour is adjusted over an artery. At
the same time record the resj irat'ions, and note in the tracing (tig. 212) how

^1

1 "^'

1 1 . : 1 1 II' l.._J 1 1-

Fig.

.—P. Tracing of the radial pulse : H. Of the cardiac impulse ;
T. Time in seconds.

the number and form of the pulse-beats vary during inspiration and expira-
tion— tlie number being greater during inspiration.

(c.) Take a tracing of the radial pulse and the cardiac impulse simultane-
ously (fig. 213).

LXI.] PULSE. 291

9. Meiocardia and Auxocardia (Ceradini).

(a.) Bend a glass tube about 20 mm. in dian)*^U'i into a semicircle, with
a diameter of about 6-8 iuelics. Taper oH' one end in a gas- flame to fit a
nostril, and draw out the other end of the tube to about the same size.
Round oH the edges of the glass in a gas-flame.

{h.) Fill the tube with tobacco smoke, place one end of it in one nostril,
close the other nostril, cease to breathe, but keep the glottis open. Observe
that the smoke is moved in the tube, passing out in a small puff during
auxocardia, i.e., when the heart is largest; while it is drawn farther into
the tul>e during meiocardia, i.e., when the heart is smallest.

These movements, sometimes called the " cardio-pneumatic movements,"
are due to the variations of the Size cf the heart during its several phases of
fulness altering the volume of air in the lungs.

LESSON LXI.

PULSE— SPHYGMOGRAPHS—SPHYGMOSCOPE—
PLETHYSMOGRAPH.

1. The Pulse.

(a.) Feel the radial pulse of a fellow-student, count the number
of beats per minute ; compare its characters witli your own pulse,
including its volume and compressibility. Observe how its charac-
ters and frequency are altered by (i) muscular exercise; (2) a
prolonged and sustained deep inspiration ; (3) prolonged expira-
tion ; and (4) other conditions.

{!>.) Feel the radial pulse-beat and heart-beat (the latter ovei the
cardiac impulse) simultaneously. Note that the former is not
synchronous with the latter, the pulse-beat at the wrist occurring
about ^ second after the heart-beat, i.e., the pulse-wave takes this
time to travel from the heart to the radial artery.

(r-.) Listen to the heart-sounds at tne same time that the radial
jiulse is being felt. Note that the pulse is felt after the first sound
about midway between the first and second sounds.

('/.) By appropriate recording apparatus one can readily show
that the pul.se is not .^inudtaneous throughout the arterial system :
thus the carotid precedes the femoral, &c.

2. Sphygmograph.— jNfony forms of this instrument are in use.
Study the forms of INIarcy and Dudgeon.

Mareys Sphygmograph (fig. 21 4) — Application of.

{(I.) CaTise the Daticnt to seat himself beside a low table, and
place his forearm on the double-inclined plane (fig. 2 1 4), which,
in the improved form of the instrument, is the lid of the box so

292

PRACTICAL PHYSIOLOGY.

[lxl

made as to form this plane. The fingers are to be semiflexed, so
that the back of the wrist, resting on the plane, makes an angle
of about 30° with the dorsal surface of the hand.

{b.) Mark the position of the radial artery with ink or an aniline

Fia. 214.— Marey's Sphygruograph applied to the Arm.

pencil. Wind up the clock (H), apply the ivory pad of the instru-
ment exactly over the radial artery where it lies on the radius, and
fix it to the arm by the non-elastic straps (K, K). The sphygmo-
graph must be parallel to the radius, and the clockwork next the
elbow. Cover the slide with enamelled paper, smoke it, fix it in
position, and arrange the writing-style (C') to write upon the
smoked surface (G) with the least possible friction. Regulate the

Fig. 215.— Tracing taken from the Radial Artery by means of Marey's Sphygmograph.
A. A hard, and B, a softer pulse.

pressure upon the artery by means of the milled head (L), /.«,,
until the greatest amplitude of the lever is obtained.

(''.) !Set the clockwork going, and take a tracing. Fix it, write
the name, date, and pressure, and study the tracing (fig. 215).

lxl]

SPHYGMOGRAPHS.

293

Fig 2i8.-Iudwig's Sphygmograph, made by Petzold of Leipzig.

294

PRACTICAL PHYSIOLOGY.

[lxi

3. Dudgeon's Sphygmograph (fig. 216).

Adjust the instrument on the radial artery by means of an
elastic strap, carefully regulating the pressure — which can be gradu-
ated from 1-5 ounces — by means of the milled head. Smoke
the band of paper, insert it between the rollers, and take a tracing.
Study the tracing (fig. 217).

FlO. 219. — Ludwig's Support for Arm for the Sphygmograph.

4. Ludwig's Sphygmograph, —Use this instrument (fig. 218).
It is not unlike a Dudgeon's sphygmograph, but there is a frame
adapted to the arm, and an arrangement for keeping the arm steady
while the hand grasps a handle for the purpose.

By the device shown in fig. 219 the arm is kept quite steady
and always in the same position. In fact, we find it most con-
venient for taking tracings with either Dudgeon's or Ludwig's
sphygmograph. It has also been found most valuable for clinical
work. It i.s made by Petzold of Leipzig.

ADDITIONAL EXERCISES.

5. Action of Amyl Nitrite.

(rt.) With the sphygmograjih adjusted, take a tracing, and then place <m;o
drops — iwt more — of amyl nitrite on a handkerchief, and inhale the vapour.

LXII.]

RIGID AND ELASTIC TUBES.

295

Within fifteen to thirty seconds or thereby it will affect the pulse, lowering
the tension, the tracing presenting all the characters of a soft-pulse tracing,
with a well-marked dicrotic wave.

6. Gas Sphygmoscope (fig. 220).

Connect the inlet tube of the instrument with the gas supply, light the
gas-flame (6). Aj)ply the caoutchouc membrane (a) over the radial artery,
and observe how the fiame rises and falls with each pulse-beat. Take a deep
expiration, and observe the dicrotism in the gas-flame.

Fig. 220. — Si^niund Mayer's Gas Sphygmoscope, made by Rothe of Prague.

7. Plethysmograph. —Use the air-piston recorder of Ellis, and take a
plethysmographic tracing of the variations of the volume of a finger. The
piston of the recorder must be lubricated with an essential oil, e.g., clove.

*<. Delepine'8 Gas Sphygmoscope is convenient. {Brit. Med. Jour., July
1891.)

9. Influence of the Bespiration on the Pulse.

(i. ) Miiller's Experiment. — Close the mouth and nostrils and then make
a forced prolonged inspiratory effort. Before doing so, feel the pulse, and
keep feeling it. Xote now the cessation of the pulse-beat. The intra-
thoracic vessels are filled with blood, and the distended auricles are unable
to contract.

(ii. ) Valsalva's Experiment. — Make the experiment as before, but make
a prolonged vigorous expiration. Xote fall in pulse-beats.

LESSON LXII.

RIGID AND ELASTIC TUBES — PULSE-'W AVE —
SCHEME OF THE CIRCULATION-RHEOMETEE.

1. Rigid and Elastic Tubes. — To the vertical stem of a glass
U-tube or three-way tube, i era. in diameter, fix an elastic pump
whose opposite end dips into a vessel of water. To the other

296 PRACTICAL PHYSIOLOGY, [lXII.

slightly curved ends of the tube fix a glass tube, 90 cm. or thereby
in length, and to the open end of the tube attach a small short
piece of india-rubber tubing with a clamp over it. To the other
limb attach an india-rubber tube of the same diameter and length
as the glass tube, and fix a clamp over its outflow end. Pump
water through the system. The pump may be compressed directly
by the hand, or it may be placed between the two blades of a
"lemon-squeezer," and the extent of the excursion of the latter
regulated by a screw.

(a.) Rigid Tube. — Clamp ofi" the elastic tube near the U-piece.
AVork the pump about forty beats per minute, and force water into
the glass tube. The water flows out in jets in an intermittent
stream corresponding to each beat. Gradually clamp the outflow
tube, and keep pumping ; the water still flows out in an intermit-
tent stream, and no amount of diminution of the outflow orifice
will convert it into a continuous stream ; as much water flows out
as is forced in. All that happens is, that less flows out, and, of
course, less enters the tube. Instead of the clamp at the outflow,
a tube drawn to a fine point may be inserted.

{h.) Elastic Tube.— Clamp off" the glass tube near the U-piece,
and unclamp the flexible one so as to have no resistance at its out-
flow end. AVork the pump ; the outflow takes place in jets cor-
responding to each beat of the pump. Pump as rapidly as possible
and the outflow stream will still be intermittent. While pumping,
gradually clamp the tube at its outflow so as to introduce resistance
there — to represent the resistance in the small arterioles— and when
there is sufficient resistance at the outflow, the stream becomes a
uniform and rontinuous one. Feel the tube ; with each beat a
pulse-beat is felt. The resistance at the periphery brings the
elasticity of the tube into play between the beats, and thus con-
verts the interrupted into a uniform flow. This apparatiis serves
also to demonstrate why there is no pulse in the capillaries, and
under what circumstances a pulse is propagated into the capillaries
and veins.

2, Velocity of the Pulse-Wave.

{a.) Take 3 metres ofiiidiaruViber tubing 6 mm. in diameter. To one end
of the tube attach the ball of a Higginson's syringe (elastic pump) to imitate
the heart, while the other end of the tube is left open, with a clamp lightly
fixed on it. Arrange to pump water through the tube. Arrange two light
levers on one stand, and place a ])art of the tube near the pump under the
lower lever, and resting on a suitable sujiport, while part of the tube near
the outflow end is similarly arranged under the upjier lever. Regulate the
pressure of the lever upon the tube by means of lead weights.

(6.) Arrange on the same stand a Despretz's chronograph to record the
vibrations of an electro-tuning- fork (30 or 50 D.V. per second), with the
writing points of the two levers and chronogia])h writing upon the drum in
the same vertical line.

LXTI.] RIGID AND ELASTIC TUBES. 297

(c.) Set the tuning-fork vibrating, allow the drum to move, compress the
elastic pump interru{)tedly — to imitate the action of the heart — and propel
water through the tube. The compression may be done by means of a lemon-
squeezer, the extent of the excursion being regulated by a screw, and, to
secure regularity, arrange the number of pulsations to the beating of a
metronome. On doing so, as one pumps in water, the tube distends and
I'aises the lever ; in the interval between the beats, as the water flows out
at the other end, the tube becomes smaller, and the levers fall. Feel the
tube ; with each contraction of the pump, a beat — the pulse-beat — can be
felt.

(d.) Fix and study the tracing. The tracing due to the rise of the lever
next the pump begins sooner, and is higher than the one from the lever near
the outflow. Make two ordinates to intersect the three tracings, one where
the lower pulse-curve rises from the abscissa, and the other where the u])per
curve begins. Count the number of D.V. of the tuning-fork between these
lines. Measure the length of the tube between the two levers, and from
these data it is easy to calculate the velocity of the pulse-wave in feet per
second.

3. Scheme of the Circulation. — Use either Rutherford's scheme
or the major schema. In the latter, the heart is represented by
an elastic pump (Higginson's syringe), the arteries by long elastic
tubes dividing into four smaller tubes with clamps on them ; two
of the tubes leading into tubes filled with sponge to represent the
capillaries. The capillaries lead into a tube with thinner walls
representing the veins. The inflow tube into the heart and the
outflow tube at the vein are placed in a basin of water, and the
whole system is filled with water.

('^) Use two mercury manometers, connect one with the arterial,
and the other with the venous tube. Adjust a float on each, and
cause the writing points of the two floats to write exactly one
below the other in the same vertical hne on a drum.

(b.) Unclamp all the arteries, and work the pump, regulating
the number of beats by means of a metronome beating thirty per
minute, and compress the heart to the same extent each time with
a lemon-squeezer. Both manometers will oscillate nearly to the
same extent with each beat. Take a tracing on a slow-moving
drum.

(r.) Gradually clamp the arteries to offer resistance, and con-
tinue to pump ; the pressure in the arterial manometer will rise
more and more with each beat until it reaches a mean level with
a slight oscillation with each beat. The pressure in the venous
manometer rises much less, and the oscillations are very slight or
absent.

(</.) While the mean arterial pressure is high, cease pumping ;
this will represent the arrest of the heart's action, brought about
by stimulation of the peripheral end of the vagus ; the arterial
blood-pressure falls rapidly.

298

PRACTICAL PHYSIOLOGY.

[lxil

(e.) Begin pumping again until the mean arterial pressure is
restored, and then unclamp gradually the small arteries. The
steady fall of the blood-pressure represents the fall obtained when
the central end of the depressor nerve is stimulated (the vagi
being divided).

(/.) Two sphygmographs may be adjusted on the arterial tube,
one near the heart and the other near the capillaries, tracings
being taken and compared.

ADDITIONAL EXERCISES.

4. Rigid and Elastic Tubes. — Arrange an experiment as shown in fig. 221.
The flask should at least hold a litre, and be arranged as a Marriotte's flask.
The tubes — one of glass and the other of caoutchouc— have the same diameter,
and the outflow orifices are of the same size. The glass tube is attached by a
short elastic tube to the lead tube coming from the reservoir. As the fluid

Fig. 221. — Marey's Scheme for showing that in the Case of Rigid and Elastic Tubes of the
same Calibre, under certain Conditions, the Elastic Tube delivers more Fluid than
the Rigid one.

flows into the tubes, they are compressed rhythmically to imitate the inter-
rupted beat of the heart. Observe that more fluid is discharged by the elastic
than by the rigid tube.

5. The Rheometer (fig. 222) is used to measure the amount of blood
flowing through a vessel in a given time, and, therefore, the diameter of the
vessel being known, to estimate the velocity or rate of blood-flow through an
artery. The nozzles of the instrument are inserted and tied into the artery
of an animal, but as the student is not permitted to do this, use an india-
rubber tube to represent the artery.

LXII.]

RIGID AND ELASTIC TUBES.

299

(a.) To represent the heart — or the weiglit of a column ot fluid — arrange
a Marriotte's flask or funnel on a stand, and to the outflow tube attach a
narrow india-rubber tube, and clamji it alter Hlling it with normal saline
(to represent defibrinated blood). Fill one bulb of the instrument with
defibrinated blood, the other with almond oil, and close the top of the
instrument with a glass plug.

(h.) Suppose the tube to represent an exposed
artery ; about the middle of the tube apply two
ligatures about an inch apart (or two clamps).
Divide the part of the tube included between the
two ligatures, and tie into either end the nozzles
provided with the instrument. Call the one
next the reservoii- or heart /t, and the other on 3
t. Fix the instrument into the nozzles, the
bulb A being filled with oil and in connection
with /;, B with defibrinated blood and connected
with A-. The instrument is fixed in position by a
support provided with it, while a handle which
fits into two tube-sockets on the upper surface of
the disc (c, e,) is used to rotate the one disc on
the other.

(c. ) All being now ready, take the clamp off
the reservoir of blood and the clamps or ligatures
ott'the artery. The defibrinated blood flows into
the bulb A, displaces the oil in it towards B,
the defibrinated blood of B being forced out into
the artery and caught in a suitable vessel. Of
course, in the animal this blood simply passes
into the artery. As soon as the bulb A is filled
with blood, w'hich is indicated by a mark on
the glass, the disc is suddenly rotated by the
hand, whereby B communicates with h, and A
with /•. The blood now flows into B, displacing
the oil in it into A, and as soon as this takes
])lace, the disc is again rotated. This process is
repeated several times. Count the number. The
bulbs have the same capacity and are exactly
calibrated.

The time is most conveniently measured by
connecting the rheometer with an electro-magnet
registering on a drum each rotation of the disc,
and under this a time-marker records seconds.

Example. — Sujipose each bulb holds 5 cc, and
suppose the bulbs to be filled ten times with
blood during 100 seconds, i.e., 50 ecm. flowed
from the tube in i second. Suj)j)ose the diameter
of the tube to be 2 mm. {i.e., radius = i mm.),
this would give a sectional area of 3. 14 mm.

The velocity (V) is calculated by the ratio of
the quantity discharged (Q) to the sectional area (S), i.f., the quantity of fluid
flowing across any section in unit of time -r area of that section. Hence —

s

.5 cc, or what is the same thing, 500 cmm., are discharged in one second ;

therefore the velocity is = ~ — = 159 mm., or about six inches per second.
3.14

Fig. 222.— Rlieometer.

300 PRACTICAL PHYSIOLOGY, [LXITI.

6. To familiarise himself with this calculation, the student would do well
to estimate the amount of water discharged from a tube of known diameter.
Let the tube be attached to a litre-bottle arranged as a Marriotte's flask.
Estimate the amount of fluid discharged in a given time, and from this
calculate the velocity of the flow in the tube.

LESSON LXIII.

CAPILLARY BLOOD-PRESSURE— LYMPH-HEARTS
—BLOOD-PRESSURE AND KYMOGRAPH.

1. Blood-Pressure in the Capillaries.

(a.) Make the following apparatus (fig. 223), consisting of a disc
of glass, 2 cm. long, 3 to 4 mm. broad, and i mm. thick, and on its
under surface fix with cement a glass plate {a), with a surface of
5 mm, square. Two threads supporting a paper scale-pan are
attached to the glass disc. Arrange the glass plate (a) over the
skin on the dorsal surface of tlie middle finger, just at the root of
the nail. Add weights to the scale-pan until the skin becomes pale.
Note the weight necessary to bring this about, but observe that the
skin does not become pale all at once.

(h.) Test how altering the position of the hand affects the pressure
in the capillaries.

2. Destroy the brain of a frog. Very slightly curarise it.
Examine microscopically the circulation in the web of its foot and
in its mesenteric vessels.

Apply a drop of croton oil or mustard for a minute or less.
Observe the inflammation thereby produced, and the changes in
the appearance of tlie blood-vessels and the blood-flow, until the
latter is finally arrested in a condition of stasis, and exudation takes
place.

3. Posterior Lymph-Hearts.

(a.) Destroy the brain of a frog, place it on its belly, and watch
the beating of the posterior pair of lymph-hearts, whicli are
situated one on eacli side of the urostyle in the triangle between
coccygeo-iliacus (ic), gluteus ((/I), origin of the vastus externus (ve)
and pyramidalis (p) muscles (fig. 224).

(b.) Kemove the skin covering them, taking care not to cut too
far outwards, else a cutaneous vein will be injured and bleed freely.
Count the number of beats per minute, noting that the rhythm is

LXIII.]

CAPILLARY BLOOD-PRESSURE.

301

not synchronous with the blood-heart, whose movements can
usually be distinguished without opening tlie chest.

(c) Destroy the posterior part of the spinal cord with a seeker
or wire, and observe that the rhythmical automatic movements of
the lymph-hearts cease.

4. Estimation of the Blood-Pressure by Ludwig's Kymograph.

— As students are not permitted to perform experiments upon live
animals, the most they can do in this experiment is to arrange the
necessary apparatus as for an experiment, and to make the necessary
dissection on a dead animal.

Fig. 223. — Apparatus
used by V. Kries
for Estimating the
Capillary Blood-

Pressure.

Fig. 224.

-Posteiior Pair of Lymph-Hearts (L)
of the Frog.

A. {11. ) Arrange the recording apparatus for a continuous tracing. The
clockwork is wound up, and the drum is so adjusted that, when it moves, it
unwinds the continuous white paper from a brass bobbin placed near it.
Arrange a time-marker connected with a clock, provided with an electric
interrupter, to mark seconds at the lower part of the paper. It is usual to
use a pen-writer charged with a .solution of aniline (red or blue), to which a
little glycerin is added to make it How freely.

{I).) Partially fill the manometer with dry clean mercury, and in the open
limb of the manometer place the Hoat, provided with a pen or sable brush
moistened with aniline ink containing a little glycerin. See that the float
rests on the convex surface of the mercury (fig. 225).

('•.) The closed or jiroxinial side of the manometer at its ujiper part is like
a T-tube, the stem of which is connected by thick india-rubber tubing to a
piece of flexible lead tubing ; on the free end of the latter is tied a glass
cannula of considerable size, and over the india-rubber tubing connecting
the cannula with the lead tube is placed a clamp. The proximal end of the

302

PRACTICAL PHYSIOLOGY.

[lxiii.

manometer is tilled by means of a syringe with a saturated solution of sodium
carbonate as high as the stem of the T-jiiece. To it is attached a long india-
rubber tube, which is connected witli a ])ressure-bottle tilled with a saturated
solution of sodium carbonate, and kejit in position by a cord passing over a
j)ulley fixed in the roof. A clam]) compresses the india-rubber tube just
above the manometer. Open this clamp and also the one at the end of the
lead pipe. The alkaline solution fills the whole system, and after it does

so, and no air-bubbles are present,
t/~\ close the clamp at the end of the

lead tube, and then the one on the
pressure-bottle tube. It is well to
have an inch or more of positive
pressure in the manometer. See
that the writing-style writes smooth-
ly on the paper, and that it is ke])t
in contact with the latter by a silk
thread with a shot attached to its
lower end.

B. Insert the Cannula. — (n.)
ArraiKje the necessary inslrtiinoits
in order on a tray- — scissors, scaljiels,
forceps (coarse and fine), seeker,
well-waxed ligatures, small aneurism
needle, bull-dog forceps, cannulae,
sponges.

(b.) Make the necessary dissection
on a dead rabbit. Fix the rabbit
in a Czermak's holder, as would be
done if the animal were alive. Clip
away with a pair of scissors the hair
over the neck, and with a moist
sponge moisten the skin to prevent
any loose hair from flying about.
Pinch up the skin on one side of the
trachea, between the left thumb and
forefinger, and divide it with a
sharp scaljjel. This exposes the
fascia, which is then torn through
with forceps ; draw the sterno-
mastoid aside, and gently separate
the muscles with a "seeker" until
the carotid, accompanied by the
vagus, dejiressor, and sympathetic
nerves is seen. The dissection is
made below the level of the larynx.
Lying just external to the carotid
is the vagus. After raising the carotid, under it, and internal to the vagus,
are seen two fine nerves ; the more internal and finer one is the de] ressor
or superior cardiac branch of the vagus (fig. 226), the other is the sympathetic.
Note that the smallest of the three nerves is the depressor, which is easily
isolated from the sympathetic by means of a seeker. If in doubt, trace
the sympathetic upwaids until it merges into the large swelling of the
superior cervical sym])athetic ganglion. The depressor should be tied low
down in the neck and divided below the ligature, as if tor an ex|)eriment on
its function. It is an afferent nerve, and therefore its central end must be
stimulated.

FlO 225.— Simple Form of Kymojiraph. On
the right is the manometer, the tlnat re-
CDriling the movements of the mercury on
a simple revolving cylinder.

Lxiir.]

CAPILLARY BLOOD-PRESSURE.

303

/.

,i

r

The vagus sliould also be isolated and ligatured as if for ex{>erimeut. It is
well to use shielded electrodes, such as afe shown in fig. 227, The vagus is
tied and divided, and if its peripheral
end is to be stimulated, the j)eri-
pheral end is drawn * through the
shielded electrodes, which are then
connected with the secondary coil of
an induction machine. To complete
the arrangements, an induction
machine ought to be set up.

(<•:) Open the sheath, and with the
seeker carefully isolate about an inch
of the carotid. Pass a ligature under
the artery by means of a tine aneurism
needle, withdraw the needle, and
ligature the arteiy. About an inch
on the cardiac side of the latter,
clamp the artery with bull-dog
forceps. Raising the artery slightly
by the ligature, with a tine-pointed
pair of scissors make an oblique
V-shaped slit in the artery, and into
it" introduce a suitable glass cannula
with a short piece of india-rubber
tubing tied on to it. Place another
ligature round the arterv, and tie it
round the artery and over the
shoulder of the cannula. The point
of the cannula is of course directed
towards the heart. Fill the cannula
with the soda solution, and into the
cannula slip the glass nozzle at the
end of the lead pipe, tying it in
securelj'. Unscrew the clamp at the
end of the elastic tubing. Set the
clockwork going ; if one were operating on a living animal, the next thing to
do would be to remove the clamp or forceps between the cannula in the
artery and the heart. At once the swimmer would begin to move and record
its oscillations on the paper moving in
front of it.

(rf. ) Before joining the lead tube to
the cannula, isolate the vagus, the
largest of the three nerves ; put a liga-
ture round it, and divide it above the
ligature. Isolate also the depressor
nerve, put a ligature round it low down
in the neck, and divide it between the
ligature and the heart. The latter is
easily distinguished fi'om the sympa-
thetic, as it is the smallest of the three
nerves accompanying the carotid. In
the dead rabbit the dei)res.sor may be
traced up to its origin by two branches,
one from the vagus, and the other from the superior laryngeal (fig. 226).
Moreover, if the sympathetic be traced upwards, a ganglion will be found on
it. This is merely to be regarded as an exercise for practice.

Fig. 226. — Nerves in the Neck of the Ral>bit.
a. Sympathetic; h. Hypoglossal, witli c.
its descending braiicli (degcaiidens »oni) ;
(i. Branch of a cervical nerve joining r:
e. Vagus, with /, its superior laryngeal
branch ; g and h. The origins of the supe-
rior cardiac or depressor nerve.

■^,

\asj^

Fig. 227 —Forms of Shielded Electrodes
for Stimulating the Vagus or a Deeply-
Seated Nerve.

304

PRACTICAL PHYSIOLOGY.

[lxiii.

{c. ) III every case a base line or line ot no pressure must be recorded on the
continuous paper. This indicates the abscissa, or when the mercury is at the
same height in the two limbs of the manometer.

(/".) Measure a Blood-Pressure Tracing. — Lay the tracing on a
table. Take a right-angled triangle made of glass or wood, and
place one of the sides bounding its right angle upon the abscissa,
the other side at riglit angles to this has engraved on it a milHmetre
scale. Or use a millimetre scale as in fig. 228. Read off the height
in millimetres from the base line to the lowest point in the curve

Fio. 228.— Blood -Pressure Tracing of the Carotid of a Dog, taken with Ludwig's
Mercurial Manometer.

and also to its highest point ; take the mean of the two, and
vmltiphj by hco, this wall give the )7Tean arterial pressure. Instead
of measTuing only two ordinates, measure several, and take the
mean of the number of measurements. In all cases the result has
to be multiplied by two.

(17.) Measure the blood-pressure tracing (fig. 229) of the carotid
of a dog from the base line T. It represents the effect of stimula-
tion of the vagus, and the arrest of the heart-beat, and the con-
sequent great fall of the blood-pressure.

LXIII.]

CAPILLARY BLOOD-PRESSURE.

30s

(/(.) In every kymograph tracing, notice the smaller undulations
due, each one, to a single beat of the heart, and the larger ones due
to the respiratory movements (fig. 229), In a blood-pressure trac-
ing taken from a dog with the vagi not divided, observe that the
size of the heart-beats on the descent of the respiratory wave i.s
greater, while the number of beats is less than on the ascent.

(i.) Study blood-pressure tracings obtained by stimulation of

(i.) The peripheral end of the vagus (fig. 229).
(ii.) The central end of the depressor,
(iii.) The central end of a sensory nerve.

Fig. 229. — B.P. Blood-pressure tracing of dog's carotid, stimulation of the vagus at
the indent in the line S ; T indicates time in seconds, and is the abscissa.

5. Make a Glass Cannula. — Heat in the flame of a blowpipe a piece of hard
glass tubing about 5 mm. in diameter. AVhen it is soft, take it out of the
tiame, draw it out gently for about 3 cm. Allow it to cool ; make the gas-jet
smaller, heat the tliin drawn-out part of the tube, and draw it out very slightly.
This makes a shoulder. ^Vith a triangular file just scratch the narrow part
obliquely beyond the second constricted part, and break it off. A cannula
with a shoulder and an oblique narrow oriiice is thus obtained. Round eff the
oblique edges either by a file, rubbing them on a whetstone, or heating slightly
in a gas-flame. Tie a piece of india-rubber on the other end, and the cannula
is complete. Instead of a straight glass cannula with a shoulder, the form
shown in fig. 230 may be used. It has a lateral tube, which is closed by means
of a caoutchouc tube, and is useful in this respect, that the large bulb prevents
clotting of the blood, while if clotting does occur, the clot can readily be
washed out by means of the pressure bottle through the lateral tube.

6. Effect of Vagus on Heart. — The student is not permitted to do this
experiment on a living animal It can, however, bo shown on a rabbit or cat

U

3o6

PRACTICAL PHYSIOLOGY.

[lxiv.

just killed. Expose the vagus rapidly, open the chest and observe the heart
beating, or thrust a long needle through the unopened chest in the heart, then

on stimulating the peripheral
end of the vagus with an inter-
ruj)ted current the movements
of the heart are arrested for a
short time — the heart itselt
being in diastole.

7. Effect of Swallowing on
the Heart (p. 312).

8. B. P. in Man v. Basch's
Sphygmomanometer. — This
consists of a brass capsule
covered on its open end with
sheets of caoutchouc, and con-
nected by means of a tube
with a manometer constructed

Fig. 230 —Improved Form of Arterial Cannula, by on the principle of an aneroid
Francois-Frank. A is tied into tlie artery : B is barometer. It is best to
attached to tiie lead tube of tlie manometer; „„„i„ zf i-^ fVip onuprfioial
and C, the lateral tube, is closed with an elastic fPP'y i^ to tne supeinciai
(clamped) tube. temporal artery, as there is a

bony suppoi't behind that.

One compresses the artery until the pulse beyond is obliterated, and then

reads off directly the pressure required to do this.

LESSON LXIV.
PERFUSION THROUGH BLOOD-VESSELS.

Perfusion through Blood- Vessels. — By perfusing fluids througli
the blood-vessels of tlie body as a whole, or l)y perfusing blood
or other fluids through isolated " surviving " organs, much may be
learned regarding tlie action of drugs and other conditions on
the blood-vessels. The blood-vessels of the frog and tortoise, the
excised kidney, and other organs have been used for this purpose.

Perfusion through Blood-Vessels of Frog.

(a.) Pith a frog, expose its heart, snip one aorta, and allow tlie
blood to flow out. Previously a fine glass cannula with a shoulder
on it must have been prepared. Tie the cannula into one aorta,
and let the ligature also include the other aorta.

(h.) Attach the cannula to an india-rubber tube containing normal
saline and connected with a glass funnel filled with normal saline
and held in a suitable holder, e.i/., a ring on a retort stand, placed
about 6-7 inches above the heart. See that there is no air in the
connections, and that the cannula is filled with normal saline by
means of a fine pipette before it is connected up with the pressure
tube Put a cUp on the pressure tube.

LXIV.]

PERFUSION THROUGH BLOOD-VESSELS.

307

(c.) Make a snip in the sinus venosus or venae cavae to let the
fluid run out. Hang up tlie frog on a suitable holder. Take the
clip off the pressure tube, allow the normal saline, or Ringer's fluid,
to run into the blood-vessels and to wash out all the blood, until
the saline runs clear from the veins. Collect the outflow in a
funnel which is placed in a graduated measure.

(fK) After the Ringer's fluid runs clear, collect, measure, and
record the amount, when it is constant, every five minutes.

(e.) Substitute normal saline or Ringer's fluid, to which some
drug has been added, and perfuse it. Note the eftect. If there is
an increased outflow, the blood-vessels, chiefly the arterioles, have
been dilated. If less, they have been contracted. Record the
results, and if necessary make a chart to show the result.

The water-tortoise is a very convenient animal to use, the perfusion cannula
being fixed in tlie tliiid or fourth aorta, the other- being tied. It is con-
veniently placed in a glass funnel when perfusion is being carried on.

In the flog, after a time, tliere is considerable a-dema of the lymph-sacs.

It is most important that the student should keep notes of his results. From
the results obtained, plot a curve on i)aper divided into squares. Make the base
line represent time, and the vertical lines, or ordinates, the amount of outflow.

Some substances greatly vontrad the blood-vessels, e.g., very

dilute nitric acid, and extract of the suprarenal capsules. The

latter is specially powerful in constricting the arterioles. {Schcifer

4' Oliver.) Others dilatf^ the vessels, e.specially the nitrites, y^nnr-

Perfusion Experiments.

Water-Tortoise. Fluid been

Water-Tortoise

. Fluid been

Frog. Fluid been

running

60'. Pressure,

running

60'.

Pressure,

running 20'. Pressure,

7

inches.

■>

inches.

7 inches.

Time.

Amount of Out-
flow in c.c.

Time.

Amonnt of Out-
flow in c.c.

t;.v,^ Amount of Out
■^™^- flow ill c.c.

I.O

° )1 »;

^-5 (3-0

=

'5 I •

2.50 = 14-5^ -3:;

1. 10

1. 15

= 12 1S =
= '5 hi

■-'S (3 10

=

]l \i

II II

orin
alin

1.20

,5 j = ■»

<3->5

=

8 ^ 1

3.10 = 15.57 = ■"

1.25

= " |o^

3.20

=

8 "

3.15 suprarenal extract.^

1.30

7 >a-^

325

=

3.20 = 2.5

I-3S

7 ) w -

3.30

=

I (§

3.25 = 2.0

1.40

6.5X ^

3-35

—

8 2

3.30 = 2.0

1-45

5-5 =

3.40

=

3.35 ceased.

1.50

4-5 "3

3-45

=

18 ) £2 i

1-55

4-5 l^

•^

3-50

=

"* C =5'5i

2.0

5 '5

«

3-55

=

24 ) Cc ^

2-5

6-5 £

1"

4.0

=

22 >j
22 ^

2.10

= 5-5 %
= 5 /

0

4-5

=

1 Made by Messrs

2.15

4.10

=

21 C

Willows, Francis &

•0

4-JS

=

19 a

Butler, chemists, Hol-

-2
S

4.20
4.25

I

17
14

■•3

a

boru, London.

4.30

=

12.5

4-35

=

II

0

3

4.40

=

?-5

4-45

=

0 < S5
9 ) =-S

4.50

=

4-55

=

ic > ^i

Wo

=

10 ) is

3o8

PRACTICAL PHYSIOLOGY.

[lxv.

PHYSIOLOGY OF RESPIRATION.

LESSON LXV.

MOVEMENTS OP THE CHEST "WALL — ELAS-
TICITY OF LUNGS— HYDROSTATIC TEST.

1. Movements of the Chest Walls — Stethograph.
. A. Rabbit. — (a.) Arrange a drum and time-marker. Fix a rabbit
conveniently, eg., on Czermak's rabbit-holder, or use the simpler
form of jNIalassez or Steinach, and with tapes tie on its chest Marey's
double tambour (fig. 231), connecting the latter with a recording

Fig. 231.— Mare/s Double Tambour, to be tied round the chest of a rabbit.

tambour adjusted to write on the drum. Introduce between the
receiving and recording tambours either the valve usually supplied
with Marey's ap)>aratus or a T-tube witb a screw clamp, whereby
the pressure within the system of tubes can be regulated. Take
a tracing. If one of the receiving tambours be placed over the

LXV',] MOVEMENTS OF THE CHEST WALL. 3O9

cardiac impulse, the tracing will show also the number of beats of
the heart (fig. 232).

B. Man.— (/j.) Stethograph (Marey's). — Cause a person to
expose his chest. Raise the screAv (7) of the stethograph, and fix

Fig. 232.— Stethofrrapb Tracing of a Rabbit. The tracing shows undulations due to
the beats of the heart. T Indicates time in seconds.

the plate (/) of the instrument on the exposed chest, with tapes
attached to c and d. Depress g, connect the tuhe (a) with a
recording tambour, with the same precautions as in 1, A,, and
take a tracing (fig. 234). Examine the tracing, noting the relation
between inspiration and expiration.

(c.) Polygraph (Bothe). — Use the polygraph of Rothe, record

Fio. 233.— Marey"s Stethograph,

the respiratory movements by means of the bag (fig. 208, A), and
study the tracing (fig. 234).

2. Elasticity of the Lungs.

Remove the whole of the front of the chest in the rabbit
already used. Observe the collapsed lungs. To the tracheal

3 to PRACTICAL PHYSIOLOGY. [lxV.

cannula attach an india-rubber bag such as is used with a spray-
producer, and inflate the hmgs. Cease to pump air into the lungs,
and oliserve how tliey collapse.

3. Hydrostatic Test.

Cut out the lungs and the heart. Place them in a vessel
of water. The whole Avill float, as the lungs contain so much air.
Cut off" a small piece of one lung, throw it into water, it floats.
This is the hydrostatic test. Compare a piece of pneumonic lung ;
the latter sinks.

4. Apncea. — Count the number of your own respirations per
minute. Take a series of rapid inspirations, ^ote that several
seconds elapse before the next insoiration. This is the period of
apncea.

Fig. 234.— Stethogiaph Tracing, taken with Rothe's Polygraph.

5. Deglutition Apnoea.

(a.) Test how long you can "hold your breath." Note the
time.

(h.) After a time, sip water without breathing, and note that,
under this condition, the time the breath can be held is nearly
doubled. The successive acts of deglutition influence the respira-
tory centre in the medulla oblongata, as well as the cardio-inhibitory
centre (Kronecker). The latter is referred -to at p. 312. Other
centres are influenced by sipping.

6. Voluntary Respiration. — Test in yourself how long this can
be kept up. As a rule, one cannot continue it for more than two
minutes.

7. Stethometer of Burdon-Sanderson.

[a.) Prepare a drum and time-marker as in the previous experiments.
Cause a person to expose his chest, and seat himselfconveniently. The instru-
ment is suspended by a broad band placed round the neck, the horizontal bar
being behind the body.

(b.) The most important diameters of the chest to measure are— " Those
connecting the eiglith rib in the axillary line with the same rib on the oppo-

LXVI.]

VITAL CAPACITY, ETC. 311

site side, the nianubiium steriii with the third dorsal s]>ine, the lower end of
the sternum with the eigiith dorsal spine, and the ensiforni cartilage with the
tenth dorsal si)ine.'' Measure only the first. Adjust the knob of the tambour
on one side against the eighth rib, as above, while the movable bar with its
knob is placed against the opposite corresponding rib. Connect the tambour
with the recording tambour, introducing a "r-j)iece, the stem of which is
provided with an india rubber bag and screw clamp to regulate the pressure
within the air-system.

8. Intra -Thoracic Pressure. — For practice this can be done on a dead
rabbit.

(a.) Fix the dead rabbit in Czermak's rabbit-holder. Expose the trachea,
tie into it a knee-shaped glass cannula. Make a small water-manometer or
bent U-tube with a millimetre scale attached, fill it about halt full with
coloured water, and to the proximal limb attach an india-rubber tube with a
T-piece and screw clamp, as in other ex})eriments. Connect the tracheal
cannula with tlie manometer tube, tighten the screw clamji, and see thai tlie
water stands at the same level in both limbs of the manometer.

{b.) Open both pleura.' without injuring the lungs. The lungs collajise and
the water is depressed in the proximal side of the manometer, and i-ises in the
open limb.

9. Respiratory Movements of Frog. — In the frog the air is forced into the
lungs.

(n.) Observe rhythmical movements of the muscles of the floor of the mouth
and of the muscles attached to tlie hyoid bone, the cavity of the mouth Is
thus diminished. Coincident with these are

(b.) Movements resulting in closure of the external nares, and thus the air
is forced into the lungs. At the same time, the glottis is o])ened, but the
mouth must be opened to see this.

{c. ) The act of expiration is performed by movements of the muscles of the
Hanks compressing tlie visceral contents.

LESSON LXVI.

VITAL CAPACITY — EXPIRED AIR — PLEURAL
PRESSURE— GASES OF BLOOD AND AIR.

1. Vital Capacity, — Estimate this on Hutchinson's spirometer,
i.e., take the deepest possible inspiration, and then make the deepest
possible expiration, expiring into the mouthpiece of the spirometer.
The average vital capacity is about 3700 cc. (230 cubic inches), but
it varies with age, height, sex, and practice in using the instru-
ment, &c.

2. Changes in Expired Air.

(a.) Blacks Experiment. — Place equal quantities of lime-water
in two vessels (A and B). Take a deep breath, close the nostrils,
and expire through a bent glass tube into A, The lime-water soon

312

I»IlACTlCAL PHYSIOLOGV.

[LXVj

becomes milky, owing to the large amount of carbonic acid expired
combining with the lime to form carbonate of lime. With the
elastic pump of a spray-producer pump the air of the room through
B. B remains clear and does not become turbid. Therefore the
carbonic acid must have been added to the inspired air in the
respiratory organs.

(6.) MuUer's Valves. — Arrange two flasks (A and B) and tubes as in fig. 235
with some lime-water in both. Close the nostrils, apply the mouth to the
tube, and inspire. The air passes in through A, and is freed of any CO., it

may contain. Expire, and the air
goes out through B, in which the
lime-water becomes turbid.

(c. ) Hey wood's Experiment. —
Place about two litres of water
in a basin, and in it put erect
a bell - jai\ Ascertain that a
lighted taper burns in the jar
Renew the air, place in the neck
of the jar a glass tube with
a piece of india-rubber tubing
attached. Close the nostrils, ajijjly
the mouth to the tube, and inspire.
The water rises in the belljar. Then expire, the water sinks, and the air
which was originally present above the water has been taken into and
expelled again from the respiratory ])assages. Remove the cork, and place
a lighted taper in the expired air. The taper is extinguished (lig. 236).

3. Swallowing. — Test on yourself how rapidly (few seconds)
you can swallow a large glass of water. In swallowing liquids, the
liquid is projected through the pharynx and oesophagus right into
the stomach chiefly by the contraction of the mylohyoid muscles in
the floor of the mouth {Kronecker and Meltzer).

Fig. 235.— MuUer's Valves.

ADDITIONAL EXERCISES.

4. Pressure within the Pleura. — Fix one end of a caoutchouc tube to a
water-manometer (water coloured red), and the other end to a trocar and
cannula. Thrust the trocar obliquely through an intercostal space until the
j)oint of the trocar lies in the space between the two layers of the pleura.
Observe how the level of the water rises in the j)roximal limb of the mano-
meter, indicating the negative pressure in the pleural cavity.

5. Blood Gases. — Blood yields about sixty volumes per cent, of gases to a
vacuum. The gases in the blood — CO^, 0, and N — are extracted fiom it by
means of a gas-pump. Various forms have been constructed, including those
of Ludwig, PHiiger, and Alvergniat. Study these various forms and the
principle ol their construction. It requires a considerable amount of time to
become thoroughly acquainted with the practical working of these instruments,
but this is not necessary from a student's point of view.

LXVI.]

VITAL CAPACITY, ETC.

313

(rt.) Suppose the gases of tlie blood to be extracted ; they are collected in a
eudiometer over mercury (fig. 237). Or, for practice, and merely to grasp the
principle how the relative ])roportion of the gases in a mixture is ascertained,
the student may use air containing a small <juantity of carbon dio.\ide.

(b.) Fuse a ball of potash on the end of jdatinum wire (best done in a bullet-
mould). Introduce this under the mercury into the gases in the eudiometer.
The caustic potash absorbs all the CO.j (twenty-four hours}, and the diminution
in volume represents the proportion of C0._, in the mixture.

((;.) With a curved pipette introduce a solution of pyrogallic acid into the
eudiometer containing the remainder of the gases ; this unites with the potash
to form pyrogallate of potash, wliich ra])idly absorbs the oxygen. The decrease
in volume represents the amount ot 0. Tlie remainder of the gas present
represents N.

Fig. 236.— Haywood's Esperiment.

Fig. 237.— Gases collected
over mercury. A ball of
caustic potash absorb-
ing the CO2.

There are other methods of estimating the proportion of the gases, but this
simple experiment is sufficient to explain the general principle on which such
estimations are made. Of course there are corrections for temperature and
pressure, and other precautions which require to be taken, but we do not enter
into these here. (See Appendix.)

A simple form of gas-pump has been devised by L. Hill {Journ. ofFhys., xvii.
P- 353)- l>y means of which results of sufficient accuracy are obtained from 10
cc, of blood.

6. Analysis of Expired Air by Hempel's Method.'

A burette, A (fig. 238), containing 100 cc, and graduated into tenths of
a cc, is used to measure the expired air. It communicates below by means
of an india-rubber tube with the movable tube or reservoir for water, B.
Above, A is connected to an absorption pipette bv means of a short india-
rubber tube of 1-2 mm. diameter with thick walls, and provided with a
Mohr's clip. The tube, a, is piaceu in conneetion successively with the
pipettes, px, which contain a solution of caustic potash to absorb the CO2
and fig. 239, which contains sticks of red phosphorus in water to absorb the 0.

Methods q/ Gas Analysis, hj 'W . Hempel. London, 1892.

314

PRACTICAL PHYSIOLOGY.

[LXVI.

Suppose the gas to be collected in A ; measure its amount when B is so
placed that the level of the acidulated water is equal in both.

Remove the Mohr's clip from a, raise B, and force all the air into p. Then
lower B, and withdraw unabsorbed air from p. Measure the volume of air.

Connect A now with the phosphorus pipette and force the air into it hy
again raising B. Lower B, and estimate the remaining volume of air. In
each case the difference of the volume of air corresponds to the quantity of
gas absorbed.

Fro. 238.— Henipel'B Burette connected with
a Potash Pipette to absorb the CO2.

Fro. 239. — Pipette with Phosphorus
to absorb the Oxygen.

The temperature of A can be kept constant by placing it in a wide tube
through which water is kept circulating as in a Liebig's condenser.

7. Waller's modification of Zrntz's apparatus is very convenient (Waller's
Human Physiology, 2nd Ed., p. 121). In this apparatus, the measurin'^ tube
is filled by means of a bulb, and not a long tube, and the measuring tube has
on it above a bulb whicli communicates by means of three tubes guarded by
simple ta])s ; two of these — horizontal — go to the two absorption (0 and CO2)
pipettes, while the vertical one is an outlet tube, (The apparatus is made by
Baird & Tatlock.)

LXVII.] LARYNGOSCOPE. 315

LESSON LXVII.

LARYNGOSCOPE— VOWELS.

1. The Laryngoscope is used to investigate the condition of tlie
pharynx, larynx, and trachea. Various forms are in use, but they
all consist of — ( i ) One or more small, usually circular, plane mirrors
fixed to a metallic rod at an angle of 120° ; the metallic rod fits
into a suitable handle, and is fixed by means of a screw. (2) A
large concave mirror of about 20 cm. focus, perforated Avith a hole
in the centre, and secured to the operator's forehead by means of a
circular band passing round the head. The mirror itself is fixed
in a ball-and-socket joint, so that it can be moved freely in every
direction.

A. Practise first of all on a model of the head and larynx
provided for the purpose.

B. On a Living Person. — (a.) Place the patient upright in a
chair. A good source of artificial light — e.7., a suitable Argand
lamp — is placed near the side of the patient's head, a little above
the level of his mouth. The incandescent lamp gives a brilliant,
clear, and steady light. Mackenzie's rack-movement lamp is a most
convenient form. The observer seats himself opposite and close to
the patient ; places the large mirror on his forehead, and either
looks through the central hole in it with one eye, or raises it so
that he can just see under its lower edge.

(b.) Seated in front of the patient, the observer directs a beam
of light until the lips of the patient are brightly illuminated. The
patient is then directed to incline his head slightly back^vards, to
open his mouth wide, and protrude his tongue. Place a clean
handkerchief over the tongue, and give the patient the hand-
kerchief to hold, which secures that the tongue is kept protruded
and well forward. Move the large mirror until the uvula and
back of the throat are brightly illuminated, the operator moving
his head slightly to and from the patient until the greatest
brightness is obtained.

(/•.) Take the small laryngeal mirror in the right hand, and waiin
it gently over tiie lamp to prevent the condensation of moisture on
its surface. Test its temperature on the skin of the clieek or the
back of the hand. Holding the liamlle of the mirror as one does a
pen, rapidly carry it horizontally backwards, avoiding contact with
any structures in the mouth, until its 1)ack rests against the base of
the uvula. At the same time, direct the beam of light upon the

316

PRACTICAL PHYSIOLOGY.

[lxvil

laryngeal mirror, when an inverted image of the larynx will be
seen more or less perfectly.

(d.) By moving the laryngeal mirror, not, however, pressing too
much on the uvaila, or continuing the observation for too long a
time, one may explore the whole of the larynx. Perhaps only the
posterior part of the dorsum of the tomjue is seen at first ; if so,
slightly depress the handle of the mirror, when the curved fold of
the slightly yellowish epiglottis and its cushion, with the (jlosso-
epiylottidtan folds, come into view. In the middle line are the
irue vocal cords, which are pearly white and shining, and best seen
when a high note is uttered, and between them the chink of the
r/lottis. Above these are the false vocal cords, which are red or
pink, the ary-epi'ilottidean folds, with on each side the cartilages o/
Wrisherg farthest out, the cartilages of Santorini internal to this,
and the arytenoid cartilages near the middle line (figs. 240, 241).

Fig. 240. — View of the Larynx during a
Deep Inspiration, g.e. Glosso-epi-
ftlottidean fold ; I.e. Lip and cushion
of epiglottis; a.e. Ary- epiglottic
fold; C.W., r..S. Cartilages of Wris-
berpcand Santorini ; v.c. Vocal cord ;
v.b. Ventricular band ; p.v. Processus
vocalis; c.r. Cricoid cartilage; (.
Rings of trachea.

Fig. 241.— Larynx during Vocalisation.
f.i. Fossa innominata ; h.f. Hyoid
fossa ; com. Arytenoid commissure.

{e.) Make tlie patient sing a deep or high note, or inspire feebly
or deeply, and ob-serve the change in the shape of the glottis. On
uttering a deep note, the rings of the trachea may be seen. N.B. —
Remember that what is seen by the observer in the laryngeal
mirror on his right or left corresponds to the prdie7it's left and
right. The lower part of the mirror gives an image of the more
posterior structures, while the anterior structures are reflected in its
upper part.

2. Auto-Laryngoscopy. — ^The student should learn to use the laryngoscope
on hini.'^elf. The student sits in a chair, fixes the large reflecting mirror in a
suitable holder about eighteen inches in hont of, and on a level with his
mouth. Behind and to one side of this an ordinary i)lane mirror is placed
vertically. On one side of his head he places the source of light. The light

LXVII.]

LARYNGOSCOPE.

3'7

is reflected on to the uvula by the reflecting mirror, and, on introducing the
small laryngeal mirror, by a little adjustment one sees the image of the
larynx in the plane mirror. Or one may use in a similar way the apparatus
of Foulis. In Dr George Johnson's method, the ordinary reflector is strapped
on to the forehead, and the observer places himself in trout of a toilet mirror.
In a line with and slightly behind the mirror, and on one side of the observer

Fig. 242. — Koiiig'i MaiK.nutiic Flame Apparatus.

place a lamp. By means of the reflector, the image of the fauces seen in the
mirror is illuminated. Introduce the laryngeal mirror, when the image of the
larynx is seen in the toilet mirror.

3. Analysis of Vowel Sounds.

Use Kiinig's a])p.uatus, as shown in fig. 242. Connect the tube of the
capsule with the gas supply, light the gas-jet, and sing the vowels A,
E, I, 0, U in front of the open trumpet-shaped tube shown in the figure.
With the other hand rotate the mirror (JI), and observe the serrated reflec-
tion of the flame in the mirror, noticing how the image in the mirror varies
with each vowel sounded.

3l8 PRACTICAL PHYSIOLOGV. [LXVIII.

PHYSIOLOGY OF THE CENTRAL NERVOUS
SYSTEM.

LESSON LXVIII.

REFLEX ACTION— ACTION OF POISONS-
KNEE-JERK.

1. Reflex Action. — Destroy the brain of a frog down as far as
the medulla oblongata, which should be done without loss of blood.
Place under a bell-jar a normal frog for comparison. Immediately
the frog is pithed, on pinching one of its toes, very probably the
leg will not be drawn up. After half an hour or more (by this
time it has recovered from the shock of the operation), observe —

(a.) Its attitude : the head of the pithed frog lies on the plate
on which it is placed, while in the intact frog the head is erect,
the body and head forming an acute angle with the surface on
which the frog rests.

(7>.) Its eyes are closed, while those of the intact frog are open.
The fore-limbs are either flexed and drawn under the chest, or
spread out, so that the body is no longer supported on the nearly
vertical fore-limbs, as in the intact frog, but lies flat upon the
surface of support. The legs are pulled up towards the body.

{c.) The absence of respiratory movements in the nostrils and
throat. It makes no spontaneous movements, if left entirely to
itself.

{<!.) Turn it on its back ; it lies in any position it is placed. Do
this with a normal frog ; the latter regains its equilibrium at once,
l^^xtend one of the legs ; it will be drawn up again towards the
body. Pinch the flank with a pair of forceps ; the leg of the same
side is rapidly extended, then drawn up towards the spot stimulated.
Pinch sharply the skin round the anus with forceps. Immediately
V)oth legs are pushed out and pulled up towards the body, as if to
dislodge the offending body.

2. Bend a long (6 cm.) straight pin into the form of a hook,
and push it through the tips of both jaws, and by means of the
hook hang up the frog vertically on a suitable support. At first

LXVIII.] REFLEX ACTION, ETC. 319

the legs may make a few movements, but they soon cease to do
so, and hang motionless.

(a.) Pinch the tip of any toe of the right leg ; the right leg is
drawn up. If a toe of the left leg be pinched, the left leg is drawn
up. These are unilateral reflex movements.

(b) Mechanical Stimuli. — Pinch the tip of one toe very feeniy,
perhaps only the foot will be flexed at the ankle-joint. Pinch
more strongly, and a greater reflex movement will be obtained.
It is evident, therefore, that the reflex movement varies not only
with the part of the skin stimulated (1, d.), but also with the
intensity of the stimulus. Very violent stimulation may cause
reflex movements in all the other limbs. This is due to irradiation
of the reflex movement in the cord.

3. The Latent Period (Tiirck's Method). Summation of
Stimuli.

(a.) Prepare and label dilutions of sulphuric acid containing
I, 2, 3, and 4 cc. per litre — i.e., o. r, 0.2, 0.3, and 0.4 per cen*'
of sulphuric acid (by volume) — and place some of each in lour
shallow glasses. Arrange also a large beaker of water to wash the
frog. Adjust a metronome to beat one hundred times per
minute. Cause it to beat.

(h.) Hold the frog in the left hand by means of the hook, and
in the right take a glass rod to hold one leg aside. Dip the other
leg up to the ankle into the o.i per cent, acid, and on doing so
count the number of beats before it is withdrawn from the acid.
After the leg is withdrawn, wash the leg in water to remove the
p.cid. Note the time in hundredths of a minute, i.e., the latent
period. Allow the frog to rest at least five minutes, and repeat
the experiment. Take the mean of the two observations —or, if
you prefer it, of three or more observations — and this will give the
" latent period."

(c.) Repeat with suitable intervals of repose the same experi
ment with acid of 0.2, 0.3, and 0.4 per cent., noting that, as tht,
strength of the acid increases, the latent period becomes shorter,
but not in the ratio in Avhich the acid is stronger.

('/.) If only the longest toe is dijjped into the acid, then the
summation of stimuli takes place more slowly.

4. Chemical Stimulation. (Purposive Characters of Reflex.)
(a.) In a small glass place some strong acetic acid and a few

pieces of fdter-paj^er 3 mm. square. Either when the frog is
lying on its back or while it is suspended, apply with a pair of
forceps one of the pieces of paper moistened with acid — the surplus

320 PRACTICAL PHYSIOLOGY. [lXVIII.

removed — to the skin on the inner side of the thigh. At once
the leg on that side is violently drawn up, perhaps both legs are
drawn up, and the foot of the leg first drawn up is swept over the
spot stimulated, as if to remove the piece of paper, i.e., purposive,
co-ordinated movements are executed. At once dip the frog in
water to remove the acid ; allow it to rest for some time. It is
much easier to obtain irradiation of the reflex movements by
chemical than by mechanical stimuli.

(6.) After five minutes repeat the experiment, but hold the leg
to which the acid is applied. Probably the other leg will move,
and the opposite foot will remove the irritating acid paper. Wash
the frog and allow it to rest.

(c.) Test further, by applying papers to the flank, the skin over
the gastrocnemius, &c., and in all cases characteristic but diflferent
reflex movements will be elicited, if sufficient interval for recovery
(five minutes at least) be allowed between the successive experi-
ments.

{d.) Destroy the spinal cord, all reflex action is abolished. The
nerves and muscles retain their excitability and the heart continues
to beat. Expose the heart : it beats. Muscle and nerve respond
to electrical and other stimuli.

5. Action of Strychnine.

(a.) Using a frog with its brain destroyed, inject with a fine glass
pipette or a hypodermic syringe into the dorsal lymph sac a drop
of dilute solution of acetate of strychnine (0.5 per cent.).

(b.) Observe that as soon as the poison is absorbed — i.e., within
a few minutes — cutaneous stimulation of any part of the body,
even tapping the table, excites general violent tetanic spasms, and
not co-ordinated muscular responses, of the whole body. During
the convulsive paroxysm the limbs are extended, hard, and rigid,
while the trunk is similarly afiected. The extensor muscles are
more affected than the flexors. The tetanic paroxysm passes off*,
to be soon followed by another on the slightest stimulation.
The excitability has been so greatly increased that even the
slightest stimulus applied to the skin discharges a reflex spasm,
i.e., provokes muscular responses which are maximal, so that a
minimal stimulus produces a maximal response.

(c.) Destroy the spinal cord with a seeker or long pin. At
once the spasms cease. Strychnia, therefore, acts on the cord
directly, and not on the muscles and nerves.

(d.) In another frog, divide the cord below the bulb, the brain
in front being destroyed, but the cord intact. Apply a crystal
of sulphate of strychnia to the cord. It soon causes tetanic
spasms, thus showing that strychnine affects the cord.

LXVIir.] REFLEX ACTION, ETC. 321

6. Action of Potassium Cliloride or Bromide or Chloral.

Prepare a reflex frog as in Lesson LXVIII. 1. Test the latent period
with dilute sulphuric aciii, 0.2 per cent , until constant results are obtained.
Inject 2 minims of a i per cent, solution of KCl or KBr or CjHClaO, and
after ten minutes time again test the latent period. Within a short time the
latent period will be greatly prolonged. Plot a curve of the results, the
abscissa to mark time and tlie ordinates the length ot the latent period.

7. Electrical Stimulation.

(A.) Single Indwiion Shocks.

(a.) From the secondary coil (key interposed) apply two fine
wire metallic electrodes, in the form of two loops, to the skin of the
leg, the electrodes being about .5-1 cm. apart.

(ft.) Stimulate with different strengths of current. No reflex
response. A single induction shock does not discharge a reflex
movement.

(B.) Repeated Shocks.

(a.) Leave the electrodes in situ, but adjust the coil for repeated
shocks. On applying a succession of even feeble shocks, a reflex
response is readily obtained. Make a table of the results obtained.

(/'.) Expose the sciatic nerve without injuring the adjacent parts ;
on stimulating the skin of the foot or leg as before, a reflex response
is readily obtained, but on stimulating the sciatic nerve directly
under the same conditions, there may be no response until the
current is made distinctly stronger. This result is explained (1) by
stating that the peripheral terminals are more excitable than the
nerve trunk, while others assume that in the sciatic nerve, besidas
excito-motor (reflex) fibres, there are nerve-fibres which inhibit the
action of such fibres. It is said that very strong stimulation «5i
cutaneous nerves also excites the reflex-inhibitory fibres.

('•.) Isolate any one of the nerves traversing the dorsal lymph-
sac of a fi'og, but leave a small square of skin attached corresponding
to the terminals of the nerve. Apply repeated shocks directly to
tlie nerve, in all prolxibility there will be no reflex response, but if
the skin be touched with dilute acetic acid, response will probably
take place. If, however, strong sulphuric acid be applied to the
skin, there will be no response.

8. Knee-Jerk.

(".) Sit on a chair and cross the right leg over the left one.
With the tips of the fingers or a percussion-hammer strike the
right Hgamentum patellae. The right leg will be raised and thrown
forward with a jerk, owing to the contraction of the quadriceps
muscle. An appreciable time elapses between the striking of the
tendon and the jerk. The knee-jerk is almost invariably absent in
cases of locomotor ataxia, while it is greatly exaggerated in some

X

322 PRACTICAL PHYSIOLOGY. [LXIX.

other nervous affections ; so that its presence or absence is a most
important clinical symptom.

(h.) The knee-jerk is readily obtained in a rabbit.

9. By means of the hand compress the abdominal aorta of a rabbit for a few
minutes. There results temporary paralysis of both hind-legs or ppraplegia.
Soon after the circulation is restored in the cord and lower limbs, the para-
plegia disappears.

LESSON LXIX.
SPINAL NERVE-ROOTS.

1. Functions of the Boots of the Spinal Nerves. — To expose the roots,

destroy the brain of a fi'og, lay it on its belly, and make a median incision in
the skin of the back, from the neck to the upper end of the urostyle. Turn
back the flaps of skin, and carry the incision down to the spines of the
vertebrje. With a scraper or blunt knife remove the muscles along each side
of the vertebral column, so as to lay bare the arches of the vertebrae. With
a blunt-pointed ])air of scissors, or two saw-blades parallel to each other and
fitted at a suitable distance into a handle, as devised by Ludwig, cut through
the arches of the eighth or last vertebra, taking care not to injure the nerves
within the spinal canal. Remove successively from below upwards the seventh,
sixth, and fifth vertebral arches, when the tenth, ninth, and eighth spinal
nerve-roots will come into view. The posterior roots are larger, come first
into view, and cover the anterior. The roots may be separated by a seeker.
Select the largest posterior root -the ninth — ana with an aneurism needle
carefully place a fine silk thread (say a red one) under it.

(ft. ) Tighten the ligature near the cord, and observe movement in some part
of the body. Divide the nerve between the cord and the ligature, and observe
further movements on division.

{b.) With the thread gently lift up the feriphernl or distal end of the nerve-
root, place it on well-protected electrodes, and stimulate it with an inter-
rupted current. No movement is observed in the muscles of the limb.

(c.) Select the posterior root of the eighth nerve, ligature it at some distance
from the cord, and divide it on the distal side of the ligature. There is
neither contraction of the muscles of the leg nor movement of the body.
Place the central stump, i.e., the part still connected with the cord, on the
electrodes, and stimulate it, when movements will take place in several parts
of the body.

{d. ) Divide the posterior roots from the seventh to the tenth nerves. Observe
that the leg on that side has become insensible. Turn aside the roots of
the divided nerves, and expose the anterior roots, which are very thin and
slender. Repeat the preceding ex])eriments on the anterior root of the ninth
nerve, i.e., ])lace a ligature round it, tighten the ligature, and divide the
nerve between the cord and the ligature. Stimulate the distal ■endi^ with an
interrupted current ; this causes contraction of the muscles supplied by this
root.

From the effects of section and stimulation of the nerve-roots, one concludes
that the anterior are motor, and the posterior are sensory. (E. Steinach,
" Motorische Functionen hint. Spinalnervenwurzeln," Pfliiger's Arch., Bd. 66,
p. 593.)

LXX.] KEACTION-TIME. 323

LESSON LXX.

REACTION-TIME— CEREBRAL HEMISPHERES.

Reaction-Time is the interval that elapses between the applica-
tion of a stimulus to a sense-organ and the moment the stimulus
is responded to by the individual. For simple reaction-time, or
sensori-motor reaction-time, all discrimination and choice are elimi-
nated by repeating the same sensation and using the same response.
Rutherford's results {Prac. Roy. Soc IJdin., July 10, 1894) give
rather longer periods than some German observers. He finds the
pendulum-myograph very advantageous in experiments on hearing
and touch, as successive curves can be superimposed. The mean
reaction-time he found, to be, for sight, o,2o"-o.22"; hearing,
o.i5"-o.i6"; touch, o.i4"-o.i5" (^cheek), o,i5"-o.i8" (skin of
finger).

Reaction-Time for Touch in Man.

1. Pendulum-Myograph Method ( Rutherford).

Two persons are required, and the observed person should not
see what the observer is doing.

(a.) Arrange the apparatus as in fig. 243. The stimulation is
done always at the same moment when the pendulum in its swing
breaks the primary circuit. It is convenient, as shown in the
figure, to use an electro-magnet for releasing the pendulum.

(fi.) The electrodes from the secondary coil are applied to any
part of the skin, and the observer, Avhen he feels the shock, closes
the " response key," whereby a mark is made on the glass plate.
Time should be recorded on the plate beforehand (60 or 100 D.V.
per second).

(c.) If it is desired for sound, a telephone is placed in the
secondary circuit and the observed person responds when he hears
the click at the moment of breaking the primary circuit.

Fig. 244 shov\'s the result obtained for the reaction-times for
touch by tlie pendulum-myograph method (fig. 243), chronograph 60
D.V. per second. The vertical line indicates the moment at which
an ineluction shock was given to (i) skin of left cheek; (2)
left side of neck ; (3) left upper arm at insertion of deltoid ; (4)
left little finger ; (5) dorsum of left foot at root of toes. Response
signal was always given by right forefinger. The vibrations
following each signal of response result from the momentum of the
lever (Ruiher/ord).

324

PRACTICAL PHYSIOLOGY.

[lxx.

2. Recording on Drum (also for sight and hearing).

(a.) Another method is to cause two electro-magnets with writing-
styles to record on a rapidly moving drum arranged as in fig. 245.
One signal is interposed in the primary circuit of an induction coil,
with a contact-key also in the circuit. This is the "stimulating
key."

(b.) The other electro-magnet is in connection with a battery,
a contact-key being in the circuit — the "response key." If this

Fig. 243.— Rutherford's Scheme of using FlQ. 244. — Result obtained for Simple Re-
Pendultim-Myut;raph for Estimating action-Time with Pendulum-Myograph

Simple Reaction-Time. (Rutherford). Shock applied in (i) To

skin of left cheek ; (2) Left side of

neck ; (3) Left upper arm near delroid ;

(4) Left little finger ; (5) Dorsum of left

foot.

method be used for touch, the electrodes from the secondary coil
are applied to some part of the skin, and the person marks response
with the response kej'.

(c.) If for sight, a ^v^hite piece of paper {Rutherford) is placed on
the electro-magnet style in the primary circuit, and the person
responds when he sees tliis move, which it does when the primary
circuit is made.

{(i.) If for hearing, then a telephone is introduced into the
stimulating circuit. The observer puts the telephone to his ear,

LXX.]

REACTION-TIME.

325

the other, the
at a rapid

Stim

and responds when he hears in tlic telephone the cHck of the
induction shock due to closure of the primary circuit. Of course, a
chronograpli records time.

3. Reaction-Time for Touch in Man. — Two persons and the
following apparatus art; requinid : coil, batteries, wires, two Du
Bois keys, two electro-magnets to record, and tuning-fork vibrating
100 D.V. per .second.

(a.) Arrange the experiment as in fig. 246, i.e., in the primary
circuit (single shocks), two keys arranged in the course of one
wire, and a recording electro-
magnet. Under the latter is
placed a chronograph recording
T^o"» ^^^^ point of the one
exactly under
cylinder moving
rate.

(b.) Of the two persons, A
and B, suppose B to be experi-
mented on. The electrodes
are placed say on the back of
the hand or cheek of B, and
he has control of key marked
P, while A controls 0. Begin
with 0 open, and P closed.
The observer closes 0, this
completes the primary circuit,
the style of the chronograph is
attracted, descends and makes
a slightly oblique mark on the
paper, which indicates the
moment of stimulation. As

soon as B feels this he opens key P, the primary current is broken
and the recording lever rises.

('•.) Measure the time value between the down and up movements
of the recording lever. In this case the individual operated on
knows the spot to be stimulated, but even with all his attention
the results may not be constant. The time varies with the
individual, his state of attention, fatigue, part stimulated, and many
other factors.

4. The Dilemma. — When the individual has to make a deliberate
choice between what parts of the body are stimulated, then the
reaction-time is considerably longer.

The experiment is arranged as in fig, 246, save that the wires

Fio. 245 — Arrangement for Simple Reaction-
Time (Rutherford).

326

PRACTICAL PHYSIOLOGY.

[LXX.

from the secondary coil pass to a Pohl's commutator without cross-
bars, and provided with two pairs of electrodes. Thus at will the
observer can pass the induced shock either through the one pair or
the other, the individual experimented on not knowing when the
reverser is changed.

Fig. 246.

-Reaction-Time for Touch in Man. T. Time signal in circuit with a tuning-fork,
vibrating 100 D.V. per second.

5. The Nenramoebimeter (Exver), or Psychodometer {Oherstein), consists
of two upi'iglits (S), with a horizontal axis carrying a spring (F) — which
vibrates 100 D.V. ))er second — with a writing-style at its free end (fig. 247).
A brass plate (B — h) moves in a slot, and carries a smoked glass plate (T), a
catch (DG), and a handle (H). The handle (H) pushes up the glass plate and

Fig. 247.— The Neuramoebinieter.

catch (G) until the latter meets the spring (F), and puts (F) on the stretch.
When the catch (G) is withdrawn, (F) vibrates, and if tlie style be arranged
to touch the glass, a curve is obtained on the latter.

{a.) It requires two ])ersons. Tlie observed person places a finger on the
knob (K), while the catch (G) and glass jilate are puslied up, the former to
catch on (F), and the style is arranged to write on the glass. The observed
person must not look, but close his eyes and listen.

LXX.]

REACTION-TIME. ' 327

(/'.) Tlie observer suddenly pulls on (H), thus discIiargiHg the spring (F),
which vibrates and produces a note. The moment the observed person hears
the sound, he presses the knob (K) and raises the writing-style. Of course,
a curve is recorded, and it is easy to calculate the time which has elapsed
between the emission of the sound and the reaction by the observed person.
Numerous observations must be made, and the mean taken.

(c.) The instrument may also be used for vision, i.e., when the slide (B — b)
on being moved uncovers a painted disc.

(</.) In the more complete form of tlie apparatus, a key is fixed on one side
of the apparatus, so that an electrical current is made or broken at the
moment the spring begins to vibrate. The key is jilaced in the primary
circuit of the induction-machine, and the electrodes of the secondary battery
are applied to any part of the skin, the observed person depressing the knob
(K) when he feels the stimulus. One can thus make numerous experiments
on the " Reaction-Time " from different parts of the body.

W. G. Smith has devised another simple method (see Journal of Physiology,
xvii. ; Pi-ocecdings 0/ Physiological Society, Is ov. 1894).

6. Inhibition of Equilibration Movements.

Take an uninjured frog, place it on its back, and observe that it will not
lie in this position, but immediately rights itself. Tie pretty firmly a thick
string round each upper arm. This in no way interferes with the movements
of the frog ; but on placing the animal on its back, it no longer rights itself,
but continues to lie in this position for a long time. It may be moved or
pulled by the legs, yet it does not regain its normal attitude. Notice the
modification of the respiratory movements.

7. Kircher's Experimentnm Mirabile.

(a.) Take a hen and gently restrain its movements. Bring its bill in con-
tact with a table. With a piece of white chalk draw a line directly outwards
from its bill. Hold the animal steadily for a few seconds, and on removing
the hands gently, it will be found that the hen lies
quiescent and does not move for a considerable time. It j\J/

may be rolled to one side or the other, yet it lies L ]

quiescent. / ^ \

{h.) Take a hen, gently restrain its movements, then lay / | -\ — ^

a straw or white thread over the base of its bill. In a short >-A,<

time the animal becomes quiescent. Note the alteration of CjLv — ^

the heart-beat and the depth and number of the respira- U^HM — '

tions. *"----\^f/

8. Beactions of Frog without Cerebral Hemispheres. 1 I | •

In the frog, as shown in fig. 248, the parts of the brain
are arranged one behind the other. The guide on the ^'ig. 248.-r.ra1n of
c ? i.\. ^ -n J. J.1 J. ■ 1 r ii i i Frog from aliove ;

surlace 01 the skull to the posterior end ot the cerebral o. Olfactory bulb:
hemispheres is a line connecting the front margins of the i. Cerebral heiui-
two exposed tympanic membranes. The brain may be spberes ; 2. Optic
exposed in a narcotised frog either by means of a small belTum-'i Med-
trocar or by severing the parts with a knife. After removal uUa oblongata,
of the cerebral hemispheres, place a little cotton wool in
the wound to prevent bleeding. The student is not permitted to do this
operation.

(a.) Immediately after the operation the frog lies flat on any surface with its
legs extended, but after the shock of the operation, i.e. , in about an hour, it draws
up lis legs and assumes the attitude and appearance of an intact frog, but it

328 PRACTICAL PHYSIOLOGY. .' \i^.

makes no spontaneous movements, although it responds readily to external
stimulation.

(b.) Its eyes are open and its respiratory movements continue (p. 311).

(c. ) If placed on its hack, it immediately rights itself. If placed on the
palm of the hand, or on a rough board held horizontally, it sits immovable,
but if the board be tilted, or the hand rotated, then, when a certain angle is
reached, its equililjrium is disturbed, and it begins to crawl up, until it comes
to the top, where its equilibrium is restored, and there it sits motionless.

{d.) If placed in water it makes continuous swimming movements.

(c.) It will avoid an opaque object placed in front of it, when one causes it
to jump by pinching its hind-legs.

(/. ) If held up between the thumb and forefinger of the right hand behind the
forearm, and if it be pinched, then it responds to every j)ressureby a "croak."
This is due to reflex excitation of the croaking centre. It also croaks on
stroking the skin of the back or flanks.

{g. ) It does not feed itself.

9. Optic Lobes (Inhibition).

(rt.) Expose the optic lobes in a frog, after removing the cerebral hemi-
spheres. After recovery, determine the latent period of a reflex mechanical
response of the legs by Tiirck's method (Lesson LXVIII.).

(6.) Apply a crystal of common salt to the optic lobes, and then determine
Mie latent period. It is greatly increased, or the reflex may be suppressed
1 1 together.

LXXl.] FORMATION OF IMAGE. $29

PHYSIOLOGY OF THE SENSE ORGANS.

LESSOX Lxxr.

FORMATION OF IMAGE — DIFFUSION — ABER-
RATION — ACCOMMODATION -~ SCHEINER'S
EXPERIMENT — NEAR AND FAR POINTS—
PURKINJE'S IMAGES— PHAKOSCOPE— ASTIG-
MATISM—PUPIL.

1. Formation of an Inverted Image on the Retina.

(rt.) From the fresh excised ox-eye remove the sclerotic from
that part of its posterior segment near the optic nerve. Koll up a
piece of blackened paper in the form of a tube, black surface inner-
most, and place the eye in it with tlie cornea directed forwards.
Look at an object — o.ii., a candle-flame — and observe the inverteil
image of the flame shining through the retina and choroiil, and
notice how the image moves when the candle is moved.

(/'.) Focus a candle-flame or otlier object on the ground-glass plate of an
ordinary camera for photographic purposes, and observe the small inverted
image.

(<;. ) Fix the fiesh excised eye of an albino rabbit in Du Bois-Reymond's
aj)paratus j)rovided for you, and observe tlie same phenomenon. The eye is
fixed with moist modeller's clay. Observe the effect on the retinal image
when a convex or concave lens is placed in front of the cornea. These lenses
rotate in front of the cornea, and are attached to the instrument.

2. Diffusion.

(a.) Fix a long needle in a piece of wood, or use a pencil or
penholder, close one eye, and bring the needle or pencil gradually
nearer to the other eye. After a time, when the needle is five to
six inches distant, it will no longer be distinct, but blurred, dim,
and larger.

{h.) Prick a smooth hole in a card Avith a needle, arrange the
needle at the proper distance to obtain the previous ditlusion eflect,
and now introduce the card between the needle and the eye,
bringing the curd near the eye, and looking through the hole in the
card. The needle will appear distinct and larger ; it is distinct
because the dill'usion circles are cut oft", and larger because the
object is nearer the eye.

330 PRACTICAL PHYSIOLOGY. [LXXL

('•.) In a dark room place a lighted candle or gas-burner con-
veniently, and by means of a convex lens focus the image of the
flame on a sheet of white paper. It is better to introduce a
blackened cardboard screen with a narrow hole in it between the
light and the lens. Observe that a sharp image is obtained only
at a certain distance from the lens. If the white screen be nearer
or farther away, the image is blurred.

3. Spherical Aberration,

Make a hole in a blackened piece of cardboard with a needle,
look at a light placed at a greater distance than the normal distance
of accommodation. One will see a radiate figure, with four to
eight radii. The figures obtained from opposite eyes will probably
differ in shape.

4. Chromatic Aberration. — Coloured Fringes.

(a.) With one eye fix steadily the limit between a white and
black surface (e.(j., fig. 265), and while doing so bring an opaque card
between this eye and the object (the other eye being closed). Let
the edge of the card be parallel to the limit between the white and
black surfaces, so as to cover the larger part of the pupil. The
margin next the black appears with a yellowish-red fringe when
the part of the pupil which lies next the black surface is covered,
while there is a bluish-violet fringe in the opposite condition.

(h.) Make a pin-hole in a blackened card, and behind the hole
place a cobalt glass. Look at a gas-flame through this arrangement.
The cobalt glass allows only the red and violet rays to pass through
it. Accommodate for the violet rays or approach the hght, the
flame appears violet, surrounded with a reddish halo ; on accommo-
dating for the red, or on receding, the centre is reddish with a
violet halo,

(e.) Place a strip of red paper and one of blue on a black surface.
The red appears nearer tlian the blue, because one makes a greater
effort to accommodate for the less refrangible red rays than for the
more refrangible blue or violet, and hence the red is judged to be
nearer.

{d.) V. Bezold's Experiment. — Make a series (10-12) ot concentric circles,
black and white alternately, each i mm. thick, the diameter of the whole
being about 15 mm. On looking at these cii'cles when they are placed witliin
the focal distance, one sees the white become j)ink ; to some eyes it appears
yellow or greenish. The same is seen on looking at concentric black and
white circles, or parallel black and white lines fi-om a distance outside the far
point of vision ; the white appears red and the black bluish.

(e. ) Wheatstone's Fluttering Hearts. — (i. ) Make a drawing of a red-coloured
heart on a bright blue ground. In a dark room lighted by a candle hold the
picture below the level ot the eyes, and give it a gentle to and fro motion.

LXXI.j ACCOMMODATION. 33 1

On continuing to look at the hearts, it will appear to move or flutter over
the blue background.

(ii.) On a bright blue ground make a square with black lines and subdivide
it into smaller squares. On the same ground make a series of small squares —
not coinciding with the previous ones— with red boundaries. On moving
the figure to and fro in the shade below the level of one's eyes, one sees the red
squares moving to and fro over the black ones. Some see the black moving
behind the red. (" Zur Erklarung d. fiatternden Herzen,"' A. Szili, L)u Buis
Archiv, 1 89 1, p. 157.)

5. Accommodation.

(a.) Standing near a source of light, close one eye, hold up both
forefingers not quite in a line, keeping one finger about six or seven
inches from the other eye, and the other forefinger about sixteen
to eighteen inches from the eye. Look at the 7p'ar finger ; a
distinct image is obtained of it, while the far one is blurred or
indistinct. Look at the far image ; it becomes distuict, while the
near one becomes blurred. Observe that in accommodating for the
near object one is conscious of a distinct effort.

{/>.) Ask some one to note the diameter of your pupil when you
accommodate for the near and distant object respectively. In the
former case the pupil contracts, in the latter it dilates. Ask a
person to accommodate for a distant object, and look at his eye
from the side and somewliat from behind ; the half of the pupd
projects beyond the margin of the cornea. When he looks at a
near object in the same line, and without moving the eyeball,
observe that the whole pupil and a part of the iris next the observer
are projected forwards, owing to the increased curvature of the
anterior surface of the lens.

(^.) Hold a thin wooden rod or pencil about a foot from the eyes,
and look at a distant object. Note that the object appears double.
Close the right eye ; the left image disappears, and vice vertsd.

((/.) At a distance of six inches from the eyes hold a veil or thin gauze in
front of some ])rinted matter placed at a distance of two feet or thereby. Close
one eye, and with the other one soon sees either the letters distinctly or the
fine threads of the veil, but one cannot see both equally distinct at the same
time. The eye, therefore, can form a distinct image of a near or distant object,
but not of both at the same time ; hence the necessity for accommodation.

6. Scheiner's Experiment (fig, 249).

{'I.) Prick two smooth holes in a card at a distance from each
other less than the diameter of the pupil. Fix two long fine
needles or straws in two pieces of wood or cork. Fix the" card-
board in a piece of wood with a groove made in it with a fine saw,
and see that the holes are horizontal. Place the needles in line
with the holes, the one about eight inches and the other about
eighteen inches from the card.

332

PRACTICAL PHYSIOLOGY.

[lxxi.

(?>.) Close one eye, and with the otlier look through the lioles at
the near needle, which will be seen distinctly, while the far needle
will be double, but both images are somewhat dim.

{c.) With another card, while accommodating for the vpar needle,

close the right-hand hole ;
the right-hand image dis-
appears ; and if the left-
hand hole be closed, the
left-hand image dis-
appears.

{(i.) Accommodate for
the far needle ; the near
needle appears double.
Close the right-hand hole,
and the left-hand image
disappears ; and on clos-
ing the left-hand hole,
the right-hand image dis-
appears.

(c. ) Instead of using a card
perforated with two holes, use
an apparatus so constructed
tliat one hole is covered with
a green and the other with a
red glass. Repeat the pre-
vious observations, noting the
disa])pearance of tlie red or
green image, as the case may
be.

(/.) If desired, the holes
in the card may be made one
above the other, but in this
case the pin looked at must be horizontal.

(gr.) Make three holes in a piece of cardboard, as in fig. 250, a, so that they
can be brought simultaneously before one eye, and look at a pin or needle.
One sees three images of the needle. On looking at a near object, the needles
are in the ])osition b, and at a distant object in tliat shown in c.

^ (/;.) Miles' Experiment.

(i.) Look at a pin through
a pin hole in a card. Ac-
commodate for the pin, move
the card to and fro, and note
that the pin appear* immov-
able.

(ii.) Accommodate for a
distant object beyond the pin,
and note that the pin appears to move in the opposite direction to that of
the card.

(iii.) Accommodate for a nearer object, and note that the pin appears to
move in the same direction as the card.

Fig. 249.— Scheiner's Experiment.

Fig. 250.

LXXI.] ACCOMMODATION. 333

7. Determination of Near and Far Points.

(a.) Hold a pill vertically about ten inches in front of one eye,
the other eye being closed. Look through the two lioles in the card
used for Scheiner's experiment, and when one distinct image of the
needle is seen, gradually approximate the needle to the cardboard ;
observe that it becomes double at a certain distance from the eye.
This indicates the near point of accommodation.

(/>.) Hold the card in front of one eye, and gradually walk back-
wards while looking at the needle, observing when it becomes
double. This indicates the far point of accommodation. N.B. —
The experiment (A.) succeeds best in short-sighted individuals.

(c-. ) Determine the near point with a vertical needle and card with hori-
zontal holes, and again with a horizontal needle and a card with the holes
vertical. The two measurements do not usual!)' coincide, because the curva-
ture of the cornea is usually ditterent in the two meridians.

8. Pm-kinje-Sanson's Images.

(a.) In a dark room light a candle, and hold it to one side of the
observed eye and on a level with it. Ask the person to accommo-
date for a distant ol)ject, and look into his eye from the side
opposite to the candle, and three reflected images will be seen. At
the margin of the pupil, and superficially, one sees a small bright
erect image of the candle-flame reflected from the anterior surface
of the cornea. In the middle of the pupil there is a second less
brilliant, larger, and not sharply defined erect image. It is reflected
from the anterior surface of the lens. The third image, which lies
most posteriorly and towards the opposite margin of the pupil, is
the smallest of the three, and is an inverted image reflected from
the 2>osferior snrface of the Ims. Ask the person to accommodate
for a near object, and observe that the pupil contracts, while the
middle image — that from the anterior surface of the lens — becomes
smaller and comes nearer to the corneal image. This shows that
the anterior surface of the lens becomes more convex during
accommodation.

{h.) Instead of using a candle-flame, cut two small square holes (lo mm.
scjuare) in a piece of cardboard, and behind each place a gas-flame, and observe
the three pairs of square reflected images.

(c.) Physical Experiment. — Place in a convenient ]>osition on a table a large
bi-convex lens, sujiported on a stand. Standing in front of it. hold a watch-
glass in the left hand in front of the lens and a few inches from it. Alove a
lighted candle at the side of this arrangement, and observe the tiiree images
described above. Substitute a convex lens of shorter focus, and observe how
the images reflected from the lens become smaller.

9. The Phakoscope of Helmholtz is used to (hnuonstrate the

334

PRACTICAL PHYSIOLOGY.

[lxxi.

change in curvature of the lens, more especially of the anterior
surface, during accommodation (tig. 251).

{a. ) Flace the pliakoscope in a convenient position, and darken the room.
•Two persons are required. The observed eye (patient) looks through a hole in
the box opposite to c, while the observer looks through the hole(«) at the side.
Light a lamp, ])lace it some distance from the two prisms {b, 0') in such a
position that its light is thrown clearly upon the observed eye, and the
observer sees two small bright square images of light, when the observed eye
looks straight ahead at a distant object. These are the corneal images. He
should also see in the observed eye two larger less distinct images, from the
anterior surfiux of the lens, and two smaller much dimmer images, from the
posterior surface of the lens. The last are seen with difficulty-.

(6.) Ask the patient to accommodate for a near object, viz., the pin above c,
keeping the eye unmoved. Observe that the middle image becomes smaller
and goes nearer to the corneal one, while the other two undergo no perceptible
change. At the same time the pupil becomes smaller.

FiQ. 251. — Phakoscope. a. Hole for observer's
eye ; h, b'. Prisms ; c. Carries a pin for
the observed eye to fix as its near point.'

Fig. 252. — Aiiber's Model to show
the principle of the Ophthal-
mometer.

10. Principle of Helmholtz's Ophthalmometer. —The student may con-
veniently learn the principle of this instrument from the ai)i)aratus of Auber
(fig. 252) (made by Petzold of Leipzig\ By means of the ophthalmometer
Helmholtz measured the size of Sanson's images and tlie changes in size during
accommodation. If one looks at an object through a ])late of glass in a direc-
tion at right angles to the surface of the glass, the object is seen single and in
its exact position. If, however, one looks at it obliquely or displaces the glass,
then the image ajipears disjilaced to the right or left according to the inclina-
tion of the glass plate. In Helmholtz's instrument two glass plates, as in fig.

LXXI.]

ACCOMMODATION*. 335

252, were placed one above the other, and could be rotated in opposite directions
round a vertical axis. One looks through the glass plates at two black lines
j>ainted on a sheet of glass. On looking at the two lines through the two glass
j)lates, and on rotating the latter in opposite directions, one image is dis}»laced
to the right and the other to the left, and the object appears double. One rotates
the plates until the inner edge of the one image coincides with the correspond-
ing edge of the other, so that each image has been displaced exactl}' to the extent
of the size of the object. The size of the image can be calculated, provided one
knows the refractive index of the glass plates, their thickness, and the angle
formed by them. In the ophthalmometer the extent of rotation is read off on
a disc placed outside the box which contains the glass plates.

11. Line of Accommodation, i.e., tlie eye does not accommodate
for a point, but for a series of points, all of which are equally
sharply perceived with a certain accommodation.

(rt.) Stretch a white thread about a metre long on a blackened wooden
board. Through two narrow slits, about 2 mm. apart, in a blackened card,
focus with one eye a particular part of the thread, which must be in the optic
axis. A part of the thread on the far and near side of the point tocussed is
quite distinct and linear, but beyond or nearer than this the thread is double,
and diverges fi-om the point focussed.

(/>.) Make a small black spot with ink on a glass plate, and hold it in front
of any printed matter. Bring the eye as close as possible to the glass plate
without losing distinct definition of the point. At one and the same time
only one ot the objects can be seen ; but not the point and the print equally
sharply defined. Remove the eye gradually from the glass plate, and ulti-
mately at a certain distance both the point and print will be equally distinct ;
the point and print mark the extreme limits of the line of accommodation.

12. Astigmatism is usually due to unequal curvatures of the cornea
in dift'erent meridians, i.e., the surface of the cornea is not part of
a perfect sphere. Astigmatism is not uncommon, and usually the
curvature of the cornea is greater in the vertical than in the hori-
zontal meridian. This is " regular astigmatism." In such a
" spoon-shaped " cornea a point of light is not focussed as a point —
" pin focus," but is linear or " line focus."

(a.) Draw on a card two black lines of equal thickness, intersect-
ing each other at right angles. Fix it vertically at the far limit of
accommodation and look at it, when probably either the vertical or
the horizontal line will be seen more distinctly. Test each eye
separately. The line most distinct corresponds to the meridian of
least curvature of the cornea.

(//.) Inr.tead of a cross, construct a star, the lines radiating at equal angles
from the centre, and being of equal thickness. Repeat the previous observa-
tions, observing in which meridian the lines are most distinct.

(c. ) Repeat these observations with the '"astigmatic clock" susfwnded on
the wall, or with appropriate illustrations given in Unellmi's "Test-types."

{d.) Construct a series of concentric circles of equal thickness and tint,
about one-eighth of an inch apart upon a card. Make a small hole in the
centre of the card. Look steadily at the centre of the card held at some

336 PRACTICAL PHYSIOLOGY. [LXXI.

distance. All the parts will not be equally distinct. Approach the card
towards you, noting in which diameter tiie lines appear most distinct.

{e.) This card may be used in another way. Hold the card in front of, and
with the circles directed towards the eye of another person — especially one
with astigmatism ; place your own eye behind the hole in the card and look
into the observed eye, noting the retiection of the circles to be seen in the eye.
Observe in which meridian the circles are most distinct, and if there be any
perceptible difference in the thickness and distinctness of the circles.

(/.) Draw a series of parallel, vertical, and horizontal lines of equal tint and
thickness, and about one-eighth of an inch a])art. Fix the card vertically at
a distance, and move towards it, noting whether the vertical or horizontal
lines are most distinct.

iff.) Fix a fine wire or needle vertically in a piece of wood moving in a slot,
and similarly fix another needle or wire horizontally. Move the needles
until both can be seen distinctly at the same time, when it will be found that
the needles are some distance apart ; usually the horizontal one is the nearer.

13. Diplopia Monophthalraica.

Make a small lioJe in a black card, hold it at some distance, and with one eye
look through it at a luminous point, the eye being accommodated for a distant
object. One sees either several objects (feeble light) or an irregular radiate
figure with four or eight rays. Move the pa{)er, and the long rays remain in
the same ])Osition. Compare the figure obtai.ied from the other eye. It will
very likely be different.

14. Movements of Iris. — (i.) It is an extremely beautiful experi-
ment, and one that can easily be made by looking at the white shade
of an ordinary reading-lamp, to look through a pin-hole in a card at a
uniform white surface. With the right eye look through the pin-
hole, the left eye being closed. Note the size of the (slightly dull)
circular visual field. Open the left eye, the field becomes brighter
and smaller (contraction of pupil), close the left eye, after an
appreciable time, the field (now slightly dull) is seen gradually to
expand. One can thus see and observe the rate of movements of
one's own iris.

(ii.) Pupil-Reflex.

Place a person in front of a bright light opposite a window, and
let him look at the light, or place oneself opposite a well-illuminated
mirror. Close one eye with the hand and observe the diameter of
the other pupil. Then suddenly remove the hand from the closed
eve. liclit falls upon it ; at the same time, the pupil of the other eye
contracts.

15. Pupil of Albino Rabbit.— The pupil in albinos appears red,
although in other animals it is black. In the albino it is red owing
to the absence of pigment in the choroid and iris, so that light is
admitted through the sclerotic and choroid and is reflected from
the interior of the eyeball through the pupil to the eye of the
observer.

LXXII.]

BLIND SPOT.

337

Place in fioiit of the eye of an albino rabbit a black screen with a hole in
it of exactly the same size as the pupil. Let the hole and pupil correspond
in position to each other. The pupil then appears black, as the card ttrresta
the lateral rays that tall upon the eyeball.

16. The Pupil Appears Larger than it is in Reality.

To see the pupil at its exact size, an excised uyebr^ll must be observed in
water. If a glass model of a pupil be taken, and then be covered Ly an-
other thick concavo-convex glass in shape like the cornea, the pupil at once
appears larger.

17. Lud wig's Apparatus for Vision of a Point.

The black plate (fig. 253) is fixed in the slot so that either a slit or a hole
is just above the handle of the instrument. Remove from the instrument
the carrier with the steel ])oint, and on the
bar of the instrument place the vertical
slit of the black plate (visual) near the
eye. There is a movable black plate with
a small hole in it. On looking at this
small hole through a vertical slit it appeals
oval from above downwards, while with
a horizontal slit the round hole appears
drawn out laterally. If there be tsvo small
holes near each other in the visual plate,
then at a certain distance two are seen in
the movable plate. If the movable plate
be removed, and the steel j)oint put in its
jilace, 071 using the large hole in the visual
plate, and bringing the steel point towards
the eye, after a time one ceases to see it

distinctly, or if seen it is blurred. On using the small hole in the visual
plate, the rod appears distinct (fig. 253).

18. Listing's Reduced Eye. — The various dioptric media of the eye may be
considered as equal to a single substance with a refractive index of 1.35 and
a single spherical surface of radius 5. 124S mm. The position of the nodal
point is 5 mm. behind the refractive surface, and the principal focus 1 5 mm.
behind this. This latter value is of special importance in enabling one to
calculate the size of a retinal image — the size and distance of the object being
known.

Fig. 253.— Ludwig's Apparatus for
Vision of a Point.

LESSON LXXir.

BLIND SPOT — FOVEA CENTRALIS — DIRECT
V ISION— CLERK-MAX WELL'S EXPERIMENT—
PHOSPHENES— RETINAL SHADOWS.

1. The Blind Spot.

(a.) Marriotte's Experiment. — As in fig. 254, on a white card
make a cross and a large dot, either black or coloured. Hold the
cdrd vertically about 10 inches from the right eye, the left being

Y

338

PRACTICAL PHYSIOLOGY.

[lxxil

closed. Look steadily at the cross with the right eye, when both the
cross and the circle will be seen. Gradually approach the card
towards the eye, keeping the axis of vision fixed on the cross. At a
certain distance the circle will disappear, i.e., when its image falls on

+

Fro. 254. — Marriotte's Experiment.

the entrance of the optic nerve. On bringing the card nearer, tlie
circle reappears, the cross of course being visible all the time.

{b.) Perform the experiment in this way. Place the flat hand vertical to
the face, and with its edge touching the nose so as to form a septum between
the two fields of vision. Fix the cross in fig. 255, keep both eyes open, and

+

FlO. 25s.

on moving the paper to and fro at a certain distance both black dots will
disa})pear.

{c.) Close the left eye, and fix the point a (fig. 256) ; or. moving the paper a
certain distance (about 16 cm. ), one sees a complete cross, and to most observers
the horizontal bar appears uppermost.

Fio. 256

(d. ) Volkmann's Experiment on the Blind Spot.

Look at the spot a (fig. 257) with one eye, the gap, b c, disappears when it
falls on the blind spot and the line looks continuous ; the points b and c appear
as if placed in the same point of the field of vision, so that the parts of the

LXXII.] DIRECT VISION. 339

retina in the periphery of the blind spot behave as it two diametrically
opposite points approached each other,

2. Map out the Blind Spot.

Make a cross on the centre of a sheet of white paper, and place it on
a table about lo or 12 inches from you. Close the left eye, and look
steadily at the cross with the riglit. Wrap a penholder in white paper,
leaving only the tip of the pen-point projecting ; dip the latter in ink, or dip
the point of a white feather in ink, and keeping the head steady and the axis
of vision fixed, place the pen-point near the cross, and gradually move it to

V 1

c d

Fig. 257— Volkmann's Experiment on the Blind Spot.

the right -until the black becomes invisible. Mark this spot. Carry the
blackened point still farther outwards until it becomes visible again. Mark
this outer limit. These two points give the outer and inner limits of the
blind spot. Begin again, moving the pencil first in an upward and then in a
downward direction, in each case marking where the pencil becomes invisible.
If this be done in several diameters, an outline of the blind spot is obtained,
even little prominences showing the retinal vessels being indicated.

3. Calculate the Size of the Blind Spot.

Helmholtz gives the following formula for this purpose : — When / is the
distance of the eye from the paper, F the distance of the second nodal
point from the retina — usually 15 mm. — rf the diameter of the sketch of tiie
blind sjiot drawn on the paper, and D the corresponding size of the blind
spot : —

/ d_
F " D

4. Acuity of Vision of the Fovea Centralis.

{(t.) On a horizontal plane -a blackboard— describe a semicircle with a
radius equal to that of the near j)oint of vision, and fix in the semicircle pins
at an angular distance of 5 a})art. Close one eye, and with the other look at
the central pin ; the pins on each side will be seen distinctly ; those at 10'
begin to be indistinct, while those at 30 to 40" are not seen at all.

[b.) At a distance of 5 feet look at a series of vertical parallel lines alter-
nately black and wliite, each .5 mm wide. A normal eye will distinguish
them ; if not, approach the object until they are seen distinctly.

5. Direct Vision. — AVIilmi tlie image of an object falls on the
fovea centralis, we liave " direct vision." "When it falls on any
other part of the retina, it is called "indirect vision." Vision is
most acnte at the fovea centralis of the yellow spot.

(a.) Standing about 2 feet from a wall, hold np a pen at arm's
length between you and the wall. Look steadily at a fixed spot
on the wall, seeing the pen distinctly all the time, Move the pen
gradually to one side ; first one fails to see the hole in the nib, and
as the pen is carried outwards one fails to recognise it as a pen.

340

PRACTICAL PHYSIOLOGY.

[lxxii.

Hence, in looking at a large surface, to see it distinctly one must
unconsciously move his eyeballs over the surface to get a distinct
impression thereof.

(b.) Make two black dots on a card quite close together, so that when
looked at they are seen as two. Hold up the left index-finger, look steadily
at it, and place the card with the dots beside the finger. Move the card out-
wards, inwards, upwards, and downwards successively, and note that as the
dots are moved towards the periphery they a])j)ear as one, but not at equal
distances from the fixed point in all meridians. For convenience, the card
may be moved along a rod, movalile on a vertical support.

6. Clerk-Maxwell's Experiment — The Yellow Spot.

A strong, watery, clear solution of chrome alum is placed in a
clear glass bottle with liat sides. Close the eyes for a minute or
so, open them, and, while holding the chrome alum solution between
one eye and a white cloud, look through the solution. An elliptical
spot, rosy in colour, will be seen in the otherwise green field of
vision. The pigment in the yellow spot absorbs the blue-green
rays, hence the remaining rays which j;)ass through the chrome alum
give a rose colour.

7. Bergmann's Experiment. — Make a series of parallel vertical
black lines, 2 mm. in diameter, on white paper, with equal white
areas intervening between them. Look at them in a good light,

at a distance of 2 to 3 yards.
In a short time the lines will
appear as in fig. 258, A. Why?
Because of the manner in wliich
the images of the lines fall on
the cones in the yellow spot, as
shown in B.

iiiiii

Fig. 258.— toergniaiin's Experiment.

8. Phosphenes.
Press the tip of the finger
firmly, or the end of a pencil,
against the inner corner of the
closed eye. A brilliant circular patch, with a steel-grey centre
and yellow circumference, is seen in the Jidd of vinfm and on the
opposite side. It has the same shape as the compressing body.
Press any other part of the eyeball ; the same spectrum is seen,
and always on the opposite side. Impressions made on the
terminations of the optic nerve are referred outside the eye, i.e.,
t>pyond into space. The phosphene is seen in the upper half if
the lower is pressed, and vice versd.

LXXII.] DIRECT VISION. 34 1

9. Shadows of the Fovea Centralis and Retinal Blood- Vessels.

Move, with a circular motion, a blackened card with a pin-hole
ill its centre in front of one eye, looking through the pin-hole
at a white cloud. Soon a punctated field appears with the out-
lines of the capillaries of the retina. The oval shape of the yellow
spot is also seen, and it will be noticed that the blood-vessels do
not enter the fovea centralis. 'Move the card vertically, when the
horizontal vessels are more distinct. On moving it horizontally,
the vertical ones are most distinct. Some observers recommend
that a slip of blue glass be held behind the hole in the opaque card ;
but this is unnecessary.

10. Purkinje's Figures.

In a dark room light a candle, and stand in front of a mono-
chromatic wall. If this is not available, hang up a large white
sheet, and while looking steadily with one eye towards the wall
or sheet, accommodating the eye for a distant object, hold the
candle close to the side of that eye, well out of the field of vision,
— downwards and laterally from the eye, — and move the candle up
and down. It is better to direct the eye outwards, keeping it
accommodated for a distant object. Ere long, dark somewhat red-
brown branching lines, shadows of the retinal vessels, Avill be seen
on a red background, due to the shadows cast by the retinal
vessels on the percipient parts of the retina. Therefore the parts
of the retina stimulated by light mu.st lie behind the retinal blood-
vessels. If the candle be moved in a vertical plane, the shadows
move upwards or downwards with the hght. If the light be moved
horizontally, the shadows move in an opposite direction.

Entoptical Vision. — By this is meant the visual perception of
objects situated within our own eye. There are many such
phenomena.

11. Muscae Volitantes.

[a.) Light a candle in a dark room ; at a distance from it place
a black screen with a pin-hole in it. Focus by means of a convex
lens the image of the flame upon the hole in the screen. Look
through the hole Avith one eye, and on the illuminated part of the
lens will be seen images of dots and threads due to objects within
the eyeball.

(b.) Rays of light proceeding from a point at or preferably within the
anterior focus of the eye, i.e., 13 mm. or less from the cornea, cast a shadow
of any object within the eyeball, because the rays fall parallel on the retina.

Make a pin-hole in a card, place it close to the eyeball, and through the hole
look at an illuminated surface, e.g., a white lamp-shade, or white sky. The
margins of the aperture become luminous, i.e. , they are the luminous body.

342 PRACTICAL PHYSIOLOGY. [LXXIL

One sees such floating objects as are present in the media of one's eye, the
" muscjE volitantes."

12. Inversion of Shadows thrown on the Retina.

Make three ])in-holes in a card, and arrange them in a triangle close to
each other. Hold the card 4 or 5 inches from the right eye, and look
through the holes at a bright sky or lamp. Close the left eye, and in front of
the right hold a pin so that it just touches the eyelashes. An inverted image
of the pin will be seen in each pin-hole. Retinal images, as we have seen, are
inverted on the retina, shadows on the retina are erect, and therefore the
latter, on being projected outwards into space, are seen inverted.

13. Duration of Impressions.

On a circular white disc, about half-way between the centre and
circumference, fix a small black oblong disc, and rapidly rotate it
by means of a rotating wheel. There appears a ring of grey on
the black, showing that the impression on the retina lasts a certain
time.

14. Talbot's Law. — A grey once produced is not changed by increased
ra{)idity of rotation of the disc exciting the sensation. The intensity of the
light impression is quiie independent of the absolute duration of the periods
of illumination and shade.

Rotate a disc like fig. 259 twenty-five times per second, then the period
in which illumination and shade alternately lasts for the inner zone is ^V sec. ,
for the middle ^^, and for the outer zone 1 J^ sec. In all three zones the period

of illumination lasts exactly one-half
of the period, and the three zones
have exactly the same brightness.
Rotate more quickly, and no further
effect is produced. The numbsr of
rotations is readily determined by
Harding's improved counter.

15. Charpentier's Experi-
ments (slow-moving discs).

(i.) " BlarJ,--band Experiment."
— Make a disc ^ white, cause it
to revolve (once in two seconds)
in bright direct sunshine. On
the wjiite sector will be seen a
Fig. 259. narrow " black band " or sector

near the black edge that has
just passed in front of the ej-'e, but separated from that edge by
a narrow white sector (fig. 260). The black band always appears
at the same time from the moment the wiiite sector appears in the
field. The time is equal to -^^ to -^^ second, i.e., 0.014" ^0 0.016".
It is independent of the velocity of the disc. Sometimes there
are two or three successive fainter bands, but they are diificult to
make out.

LXXII.]

DIRECT VIRION.

343

The first effect is wliite, followed by an after-efTect which is black
even durimj the continued white stimulus. Thus there seems to be a
slow oscillatory process in the retino-cerebral apparatus, showing a
positive and a negative phase, each phase lasting 0.014" ^0 0.016".

The negative phase of oscillation takes place after the shortest
possible illumination, and appears to be a general phenomenon.
Charpentier suggests that it is possible that a single bright stimulus.
e.g , an electric spark, appears as a double or reduplicated bright
sensation (Archives de Physiologie, 1892, p. 541). Another form
of the experiment is given in a later paper (p. 629),

Fig. 260.— Charpentier*s Disc for
" Black Band." The arrow
shows the direction of rotation.

Fig. 26r.— Charpentier's Disc for Vision
of Purple Background.

(ii.) On a large black disc (40 cm. diameter) gum near its circumference a
piece of white paper (i cm. and angular deviation i°-2^), and cause the disc
to revolve twice per second. The observer has a sen.sation of a white ribbed
streak (about \ of the entire circle) on the black surface. There is not a
uniform tint, and the ribbed appearance is due to an oscillatory process in
the retino-cerebral apparatus.

(iii.) Arrange a black disc with narrow open equidistant sectors, to rotate
opposite to a white surface illuminated by direct sunlight. The sectors have
their apices towards the })eriphery and their bases ut the centre (fig. 261)- On
rotating tho disc before the eyes so that the retina is stimulated 40-60 times
per second, i.e., when each stimulus occurs during the negative aftereffect
of the preceding stimulus, one gets a sensation of a purple-violet field, but the
field is colourless txt lower or higher rates of stimulation. Charpentier thniks
that the coloured sensation is due to entoptical vision of the retinal purple.

344

PRACTICAL PHYSIOLOGY.

[lxxiil

LESSON LXXIIL

PERIMETRY— IRRADIATION— IMPERFECT VISUAL
JUDGMENTS.

1. To Map out the Field of Vision, or Perimetry,

(a.) A rough method is to place the person with his back to a
window, ask him to close one eye, stand in front of him about 2
feet distant, hold up the forefingers of both hands in front of and

in the plane of your own
face. Ask the person to
look steadily at your nose,
and as he does so observe
to what extent the fingers
can be separated horizon-
tally, vertically, and in
oblique directions before
they disappear from his
field of vision.

{b.) Priestley Smith's Peri-
meter (fig. 262). — Let the ob-
server seat himself near a
table on which the perimeter
is placed at a convenient
height. Suppose the right eye
is to be examined, fix a blank
chart for the right eye behind
the wooden circular disc. A
mark on the hand-wheel shows
whicli way the chart is to be
placed.

(0.) The patient rests his

right cheek against the knob

on tlie wooden pillar in such a

position that the knob is about

an inch directly under his right eye, the other eye is closed either voluntarily

or with a shade, while the observer looks steadily with the right eye at the

white spot on the end of the axis of the instrument.

{d.) The observer turns the quadrant with his right hand by means of the
wooden wheel, first to one and then to another meridian. With his left he
moves the white mark along the quadrant, beginning at the periphery and
gradually approaching centralwards until it is just seen by the right eye. A
prick is then made in the chart corresponding to the angle read off on the
quadrant, at which the observer can see the white spot.

(e.) Turn the quadrant to another meridian and determine the limit of the
visual field as before. This is rejjeated for four or more meridians, and then

Fig. 262. — Priestley Smitli's Perimeter.

LXXIII.]

PERIMETRY, IRRADIATION, ETC.

345

the pricks on the chart are joined by a continuous line, when we obtain an
oval field more extensive in the outer and lower portions. Test, if desired, the
left eye, substituting a blank chart for that eye.

(/. ) Test the field of vision for colours, substituting for tlie white travelling
disc blue, red, and green. Mark each colour-field on tlie chart with a j)encil
of similar colour. Notice that the field for blue is nearly as large as tlie
normal visual field. It is smallest for green, red being intermediate between
green and blue.

(y.) With Ludwig's apparatus test when red, yellow, blue, and other
coloured glasses cease to be distinguished as such in the field of vision.

2. Binocular Vision.

(a.) Hold in front of each eye a blackened tube. On looking
through both tubes two fields will be seen. Gradually cause the
tubes to converge at tlieir free ends, and the two fields of vision will
be seen to meet and form a single field.

(/>.) Continue the convergence, and note that two fields reappear,
but they are crossed. In these " secondary positions " there is no
rotation of the eyeball on its antero-posterior axis.

('•.) If the eyeball be turned in any other direction (tertiary
positions) the after-image appears inclined, or at an angle with the
vertical or horizontal stripes, according to the original position of
the red fixation-object.

3. Wheel Movements (False) of the Eyeballs (Secondary and Tertiary
Positions).

(a.) On a grey sheet of stout [)aper, at least i metre square, rule a number
of vertical and horizontal faint
black lines. Fix on the centre of
the paper a strip of red j)aper on a
level with the eyes, the eyes being
in the primary jwsition, i.e., look-
ing straight ahead. Gaze steadily
at the latter, keeping the head
fixed. After a time suddenly direct
the eyeballs to another part of the
grey surface ; a green -blue after-
image is seen which retains its
same relative position with regard
to tiie vertical and horizontal lines,
provided the eyeballs be moved
directly ujjwards, downwards, in-
wards, or outwards, i.e., if the eye-
ball is moved up, along vertical or
horizontal meridians, the after-
iniiige is still vertical. Turn the
eyeball upwards and to the right,
or downwards and to the left, the
head being kej)t in the same jiosi-
tion, the after-image appears tilted
to the riglit : if the eyes are directed
upwards and to the left or downwards and to the right, the after-imgae appears
tilted to the left. A similar result occurs with a horizontal strip of paper,

Fig. 26j.- Appearance of a Cross in False
Wheel Movements of Eyeballs.

346

PRACTICAL PHYSIOLOGY.

[lxxiii.

but the after-images are inclined against the inclination of the vertical
images.

Suppose we look at a rectangular red cross (;;) under the same circumstances
(tig. 263), on turning the eyes, i.e., the visual line, to any vertical or hori-
zontal line passing through p, the after-image is a rectangular cross, but it
appears oblique, and its angles are neither horizontal nor vertical when the
eyes look obliquely, i.e., when the point of vision diverges considerably from
the above-named lines. The a2)pare7itly displaced crosses are shown in a, b,
c, d.

These oblique after-images were formerly regarded as showing that the
eyeball rotated on its antero-posterior axis, i.e., " ivhr.el movements." This is
not the case, the movements are only (ij)parenl. If they were real the after-
images ought to move in the same direction with both vertical and horizontal
strips, but they do not.

4. Irradiation. — By irradiation is meant the fact that, under
certain circumstances, objects appear larger than they should be
according to their absolute size and distance from the eye, larger

than other objects of greater
or less brightness of the
same size and at the same
distance.

(a.) Cut out two circles
as in fig. 264, or two squares
of exactly the same size, of
white and of black paper.
Fig. 264.— Irradiation. Place the white patch on a

black, and the black on a
v/hite sheet of paper. Hold them some distance from the eye, and,
especially if they be not distinctly focussed, the white circle will
appear larger than the black one.

Fig. 265.

Fig. 266.

{h.) Divide a square into four, as shown in fig. 265, two of the
smaller squares being white and two black. Hold the figure at
some distance from you. The two white squares appear larger, and

LXXIII.]

PERIMETRY, IRRADIATION, ETC.

347

they appear to run into each other and to be joined together by a
white bridge.

(e.) Look at fig. 266, placed at such a distance that the accommodation is
imperfect. The white stripe, which is of equal breadth throughout, appears
wedge-shaped, being wider below between the broad black patches, and
narrower above. To me also the narrow black patches appear to be broader
above and narrower below.

(d.) Gum on to a sheet of white paper two strips of black pa})er 5 mm. wide,
and parallel to each other, leaving a white interspace of 8 mm. between them.
Look at the oliject, and, especially if it be not sharply focusSed, the smaller
black strips will appear broader than the white one.

5. Imperfect Visual Judgments.

(a.) Make three round black dots, A, B, C, of the same size, in
the same hne, and let A and C be equidistant from B. Between
A and B make several more dots of the same size. A and B will
then appear to be farther apart than B and C.

(h.) Make on a white card two squares of equal size, omitting
the outlines. Across the one draw horizontal lines at equal dis-

feooofeooo

Fig. 267.

tances, and in the other make similar vertical lines. Hold them at
some distance. The one with horizontal lines appears higher than
it really is, while the one with vertical lines appears broader, z>.,
both appear oblong.

(c.) Look at the row of letters (iS) and figures (8). To some
the upper halves of the letters and figures may appear to be the
same size as the lower halves, to others the lower halves may
appear larger. Hold the figure upside
down, and observe that there is a con-
siderable difference between the two,

the lower half being considerably larger

(fig. 267).

{'t.) Zollner's Lines. — Make two lines

parallel to each other. Note that one

can judge very accurately as to their

parallelism. Draw short oblique lines

through them. The lines now no longer

appear to be parallel, but seem to slope

inwards or outwards, according to the

direction of the oblique lines.

(e.) Look at fig. 268 ; the long lines do not appear to be parallel,

although they are so.

FiQ. 268. — Zolluer's Line*.

34^ PRACTICAL PHYSIOLOGY. [lXXIIL

{/.) TI113 length of a line appears to vary according to the angle
and direction of certain other lines in relation to it (fig. 269). The
length of the two vertical lines is the same, yet one appears much
longer than the other. (A large number of similar illusions will be
found in Du Bois-Rei/mojid's Archiv, 1890,
p. 91, by F. C. Miiller-Leyer, and LAska,
p. 326.)

6. Imperfect Judgment of Distance.

(a.) Close one eye, and hold the left

forefinger vertically in front of the other

eye, and try to strike it with the right

forefinger. On the first trial one will

probably fall short of the mark, and fail

to touch it. Close one eye, and rapidly

try to dip a pen into an inkstand, or put

a finger into the mouth of a bottle placed

fiG 260.— To show False ^^ ^ Convenient distance. In both cases

Estimate of Size. one will not succeed at first. In these

cases one loses the impressions produced

by the convergence of the optic axes, which are important factors

in judging of distance.

(h.) Hold a pencil vertically about 15 cm. from the nose, fix it
with both eyes, close the left eye, and then hold the right index-
finger vertically, so as to cover the lower part of the pencil. With
a sudden move try to strike the pencil with the finger. In every
case one misses the pencil and sweeps to the right of it.

(c.) Fix a wire ring about 3 inches in diameter into the end of a rod about
2 feet in length. Hold the rod at arm's-length, close one eye, try to put
into the ring a vertical process attached to a rod of similar length held in the
other hand.

7. Imperfect Judgment of Direction.

As the retina is spherical, a line beyond a certain length when
looked at always shows an appreciable curvature.

(a.) Hold a straight edge just below the level of the eyes. Its
upper margin shows a slight concavity.

(b.) In indirect vision the aj)])Veciation of direction is still more imperfect.
While leaning on a large table fix a j)oint on the table, and then try to arrange
three small pieces of coloured paper in a straight line. Invariably, the papers,
being at a distance from the fixation-jwint, and being seen by indirect vision,
are arranged not in a straight line, but in the arc of a circle with a long
radius,

8. Perception of Size.

Fix the centre of fig. 270 at a distance of 3 to 4 cm. from

Lxxiir.]

PERIMETRY, IRRADIATION, ETC.

349

the eye, when by iiuliiect vision the broad white and black areas
of tlie periplieral parts, bounded by hyperboHc curves, will appear
as small and the lines bounding them as straight as the smaller
areas in the middle zone,

9. Convergence of the Visual Axes Influences one's Concep-
tions of Size and Distance.

(a.) Place a blackened paper tube before each eye, look at a fixed
object, and then gradually converge the tubes ; the object appears
larger and nearer.

Fio. 270.

(b.) Look at an ohject through two pieces of glass (2^x2^x5- in.), held
at first in the same j>laiie, one in front of each eye. Let the adjoining edges of
tlie two plates of glass be moved each on a vertical axis, so that they form either
a more or less obtuse angle with each other. In order to see the object dis-
tinctly the axes of the ej'eballs must converge to a greater or less extent, as
the case may be, with the result that the object appears larger or smaller, or
appears to a]i|)roach or recede as the plates are rotated. Special forms of
ajiparatus contrived by Rollett, and another by Landois, are used for tiiis
{(urpose.

350

PRACTICAL PHYSIOLOGY,

[LXXIV.

10. Apparent Movements.

(a.) Strobic Discs. — Give the discs a somewhat circular but rapid movement
and observe that the rings appear to move, each one on its own axis.

(b.) Radial Movement. —
While another person rotates
a disc like fig. 271 on the
rotating wheel, look steadily
at the centre of the disc.
One has the impression as
if the disc were covered with
circles which, arising in the
centre and gradually becom-
ing larger, disappear at the
I)ei'iphery. After long fixa-
tion look at printed matter
or at a person's face ; the
letters appear to move
towards the centre, while
the person's face appears
to become smaller and re-
cede. If the disc be rotated
in the o])posite direction,
the opposite results are ob-
tained.

(c.) Fix an object, turn
the head rapidly, and note
that the object appears to
move in an opposite direction. When the eye does not move, we judge
that a body is in motion when the image of that body falls successively on
different points of the retina, and at the same time are conscious that the
ocular muscles have not contracted {Beaimiis).

Fro. 271.

LESSON LXXIV.

KUHNB'S ARTIFICIAL EYE — MIXING COLOUR
SENSATIONS— COLOUR-BLIN DNESS.

1. Kuhne's Artificial Eye (fig. 272).

{a.) Fill the instrument with water, and place it in a darkened room with
the cornea directed to a hole in a shutter, through which sunliglit is directed
by means of a heliostat. If this is not available, use an ox3'-hydrogen lamp
or electric light to throw parallel rays of light on the cornea. If these cannot
be had, use a fan-tailed gas-burner, but in this case the illumination and
images will be feeble. To enable one to observe the course of the rays of light,
pour some eosin or fluorescin into the water in the instrument.

[h.) Formation of an image on the retina. Observe the course of the rays
of light, which come to a focus behind the lens — the principal posterior focus.
Move the ground glass representing the retina, and get a clear inverted image
of the source of light. N.B. — In this instrument accommodation is effected
not by altering the curvature of the lens, as in the normal eye, but by moving
the retina.

LXXIV.]

KOHNE's ARTmCIAL EYE.

351

(c.) Place convex and concave lenses between the source of light and the
cornea ; observe how each alters the course of the rays and their focus.

(d.) After having an image well focussed upon the retina, move the latter
away from the lens, when the image becomes blurred owing to diffusion. If,
however, a slip of zinc, Avith a hole cut in it to act as a diaphragm to cut oii
some of the marginal rays, be interposed, the image is somewhat improve 1.

(c.) After seeing that the light is sharply focussed on the retina, remove the
lens— to imitate the condition after removal of the lens for cataract— and
observe that the rays are focussed quite behind the retina.

(/.) Place the removed lens in front of the cornea, the principal focus is
now much in front of the retina, so that a much weaker lens than the one
removed hns to be used after removal of the lens for cataract.

272.— Kiihne's Artificial Eye, as made by Jung of Heidelberg.

ig.) ABtigraatism. — Fill the plano-convex glass {g)—to imitate a cylindrical
lens— with water, and place it in fiont of the cornea. Between the cornea
and the cylindrical lens place a sheet of zinc with a cross cut out in it, or with
a number of holes in a horizontal line. One cannot obtain a distinct image of
the cross or the holes, as the case may be.

(h.) Scheiner's Experiment.— With the light properly adjusted, place in
front of the cornea a piece of zinc perforated with two holes (c), i cm. in
diameter, in a horizontal line, the distance between the holes being le.ss than
the diameter of the pupil. Find the position of the retina— and there is only
one position— in which the two beams of light are brought to a focus. Mo\e
the retina toward? the cornea, and observe two images ; close the right-hand

352

PRACTICAL PHYSIOLOGY.

[lxxiv.

hole and the right-hand image disappears. Bring the retina posterior to the
prini^ipal focus, and again there are two images. On closing the right-hand
hole the left hand image disappears, and vice vrsd.

2. Hering's Apparatus for Mixing the Colours of Coloured Glasses.

By mixing two primary colours (rsd, yellow, green, blue), one may obtain
all intermediate hues, and by mixing three colours (red, green, and blue, or
yellow, green, and violet), one can obtain white. The apparatus consists of a
box k (fig. 273), two pieces of mirror glass (* and Sj ). each placed at an angle of
45° to the horizontal plane as shown in fig. 274. The base of the box consists
of a coloured glass {f^), while the lower half of the right lateral wall is
filled with the coloured glass j)late (/, ), and the upper half of the left wall by
the coloured glass jdate (/). The white gLss plates (W, W,, Wg) reflect light
through the coloured glasses (fig. 273). The light transmitted from below,

KiG. 273. — Hering's Appaiatus for Mixing
(."oloured Liglit k. Box; t, fj. Lids-
W, Wi, H'2. VTliite rellecting surfaces.

Fig. 274.— Scheme of t'ig. 273. /./i./a- Col-
oured glasses. W, Wi, W^. White reflect-
ing surfaces : s, «i. Glass plates.

and that ft'om the two sides, is transmitted by a tube to the observer's eye.
The brightness can b3 varied by adjusting the white reflecting surfaces, which
are placed opposite a well-lighted window. By means of three small metallic
doors (t, /, ) any one of the colours can be cut off". Thus any combination of
coloured lights can be made, as the glasses are movable. The writer has
found it best to put the violet or blue lowermost.

3. Mixing Colour Sensations.

(a.) Lambert's Method. — On a black background place a blue
wafer or square of blue ])aper, and 6 or 7 inches behind it a
yellow square or v/afer. Hold a plate of clear glass vertically,
about 10 inches above and midway between the two squares.
Look obliquely through the glass, and get the reflected image of

LXXIV.]

COLOUR-BLINDNESS.

353

yellow to overlap the blue, seen directly through the glass ; where
they overlap appears white. Hering has arranged a large form of
this apparatus suitable for class purposes.

{b.) Arrange on the spindle of the rotating apparatus the disc with coloured
sectors provided for you (tig. 275). On rotating the disc rapidly, observe that
it appears grey or whitisli. The disc is provided with sectors corresponding
to the colours ot the spectrum, and arranged in varying proportions.

(c.) Arrange three of Clerk-Maxwell's colour discs — red, green, and violet
— ujion the spindle of the rotating a]>paratus. Adjust the relative amounts
of these three colours, so that on rapidly rotating them they give rise to the
sensation of grey or white. Each disc is of a special colour, and has a radial
slit from the centre to the circumference. This slit enables a disc of a ditierent
colour to be slij'jied over the other, and thus many discs can be superposed,
and the amount ol each colour exposed regulated in any desired proportion.

Fig. 275.— Rothe's Rotatory Apparatus for Colour Discs. It is so arranged as to give
various rates of rotation by combining the motions of i, 2, ami 3.

('/.) Combine a chrome-yellow disc and a blue one in various proportions,
and on rotating, the resultant colour is never green, but a yellowish- or reddish-
grey.

(e.) Arrange two coloured discs of vermilion and bluish-green in the pro-
portion of 36 of the former to 64 of the latter. On the same sjiindle arrange
a white and a black disc — with a diameter a little more than half that of the
former i)air — the white being in the }iroportion of 21.3 to 78.7 of the black.
On rotating, a grey colour is obtained fiom both sets of discs.

4. To Test Colour-Brndness. — On no account is the person
being tested to be a.>^ked to name a colour. In a large class of
students one is pretty sure to find some who are more or less colour-
blind. The common defects are for red and green.

354 PRACTICAL PHYSIOLOGY, [lXXIV".

(n.) Place Holmgren's worsteds on a white background in a
good light. Select, as a test colour, a skein of a light green colour,
such as would be obtained by mixing a pure green with white.
Ask the examinee to select and pick out from the heap all those
skeins which appear to him to be of the same colour, whether of
lighter or darker shades. A colour-blind person will select
amongst others some of the confusion-colours, e.r/., pink, yellow.
A coloured plate showing these should be hung up in the labora-
tory. Any one who selects all the greens and no confusion-colours
has normal colour vision. If, however, one or more confusion-
colours be selected, proceed as follows : — Select, as a test colour, a
skein of pale rose. If the person be red-blind, he will chose blue
and violet ; if green-blind, grey and green.

(/).) Select a bright red skein. The red-blind will select green
and brown : the green-blind picks out reds or lighter brown.

5. Contrast and Simultaneous Contrast.

The following are examples of simultaneous contrast where
stimulation of the retino-cerebral apparatus modifies the sensations
excited by a different portion of the retina when the compared
objects — light or colour— are looked at simultaneously. Contrast
phenomena were carefully studied by Chevreul in relation to the
effects produced by colours juxtaposed in tapestry in the Gobelin's
factory of Paris. Contrast may apply to size, light, colour, and it
may be simultaneous or successive.

(a.) Place a small white square or oblong piece of paper or cross
on a dull, black surface. Stare steadily at the white square, and
observe that the edges appear whiter than the centre ; indeed, the
centre by contrast may appear greyish. A white strip of paper
placed between two black strips, looks white at the margin near
the black.

(/).) Look with one eye at the sky through a i-inch blackened
tube, both eyes being open. The field of vision looks much brighter
when seen through the tube than is the case with the other eye.

(r.) Place side by side a white and black surface. Cut two
oblong (i|"x2") pieces of grey, yellow, or other coloured paper
of exactly the same size, and lay one piece of the grey on the white
background, and the other on the black. Observe how much
brighter the latter looks owing to contrast. Reverse the pieces,
and notice that the same result occurs. Repeat with other
colours.

(d.) On the rotating machine cause a disc, as in fig. 276, to
rotate with moderate rapidity, when several zones will be seen, the
innermost black, while each one farther outwards is lighter in tint.
Each zone, where it abuts against the inner darker zone, is lighter

LXXIV.] CONTRAST. 355

than the rest of the same zone, and shades off gradually to tlio
outer part of the zone.

(e.) Take two pieces of different coloured paper (say pale red and
pale green) and place them side by side. Fix two similar strips
apart from each other and
distant from the other two.
The two slips juxtaposed
differ in colour from the
isolated pieces. In the juxta-
posed slips the colour of
the one influences the colour
of the other, i.e., each one
looks as if it were mixed
with a certain amount of
the complementary colour
of the juxtaposed slip
(Cf^eweul).

{/.) Place on a table a small
sheet (4" X 4") of red and one of
green j)aper. Cut out of a sheet Fiq. 276.— Disc for Contrast,

of red pa])er two pieces about

1 inch square, and place them on the two large squares. Observe that the
small red square on the green ground appears liar brighter and more saturated
than the red square on the red ground.

{(/.) Cut a small hole (5x5 mm.) in a piece of coloured paper, e.g., red,
and look through the hole at a sheet of white paper, the hole appears
greenish.

(/(. ) On a mirror jilace a slip of transparent coloured glass, e.g., red or green.
Hold in front of the coloured glass a narrow strip of white paper ; by adjust-
ing the position of the glass in relation to the light, we see two images reflected
from the anterior and posterior surface of the mirror ; one has the same colour
as the coloured glass, while the other or posterior one has the complementary
colour ; if a red glass be used the latter is green, if a green glass it is red.
Hold in front of the red glass a piece of white paper with black printed matter
on it. Tlie black print is seen green in the posterior image. Gum a few
narrow strij>s of white paj)er (i mm. in diameter) on black paper, and on hold-
ing it up in front of the red glass, as before, the anterior image appears in the
comj)lementary colour of the glass, viz., green.

(/. ) Place four lighted candles in a dark room before a white surface, and
push between the candles and the screen towards the centre of the series an
opaque screen. c.(i., cardboard, with a clean-cut vertical edge. A part of the
white surface is illuminated by all four candles, tl:en a vertical area illumi-
nated by three, and so on, and finally a part not illuminated by any of the
candles. Each of these areas is throughout its entire extent equally illumi-
nated, yet on the side where each area abuts against a darker area it a])pears
lighter, on the other side darker, and gradually shaded between its outer and
inner limits. This is due to the fact that strong stimulation of one part of
the retina diminishes the excitability in the other })arts, and the parts most
afiected are those next the excited area. Thus a change in the excitability
of one part of the retina is brought about by stimulation of an adjacent
part.

356

PRACTICAL PHYSIOLOGY.

[lxxiv.

0'.) H. Meyer's Experiments on simultaneous contrast.
(i.) Cut out a small oblong of white, or preferably of grey, paper,
and put it on a large piece of bright green paper (4 inches square) ;
the grey suffers no change. Cover the whole Avith a thin semi-
transparent sheet of tissue paper. The grey oblong appears ■jdnh.

(ii.) Instead of green paper place the grey slip on red, and cover
it as before ; a greenish -blue contrast colour is seen.

(iii.) Eepeat (a.), but place a red square on a grey ground ; the
red square will appear greenish.

(iv.) A grey square upon blue appears yellow ; a yellow upon

blue appears white, when
covered Avith tissue paper.
All the above are modifica-
tions of H. ]\Ieyer's experi-
ment. The tissue paper is
used, as contrast colours are
far more readily excited
by pale than by saturated
colours, so that differences
of sensation are much greater
with weak than with strong
stimulation.

(v.) Surround the small
square with a broad black
line, each square appears in
its own colour. The effect

Fig. 277.-Disc for Simultaneous Contrast. ^f contrast is destroyed.

{k. ) Place side by side two strips of paper, green and red (6x3 in. ). Over
the line of junction jilace a strip of grey paper (x x 6 in.), and cover the whole
with tissue paper, as before. The grey appears pink on the green side, and
greenish on the red. This contrast is also set aside by running a black
margin round the grey strij). Do the same with yellow and blue.

(/.) Arrange a disc like fig. 277 on the rotating wheel.
On a white disc fix four narrow, coloured {e.g., green)
sectors, and interrupt each in the middle, as in the
figure, with a black and white strij)e. On rotating the
disc, the ring, which one might expect to be grej' from
the black and white, appears reddish, i.e., the comple-
mentary colour of the greenish ground.

(»(.) Place a strip of grey paper -on a black background
and a corresponding strip on a white ground. The
former will appear much lighter, the grey on white
much darker. Fix the eyes for a minute on a point mid-
way between the strips ; close and cover the eyes. The
after images will show a great difference in luminosity.
(?i.) Bagona Scina's Experiment. — Two pieces of wood fixed at right angles
to each other are covered by white paper, while a coloured sheet of glass is
held at an angle of 45° between them (fig. 278), or the apparatus of Hering (fig.

Fig,

278. — Kagona
Scina's Experi
nient.

LXXIV.]

CONTRAST.

357

279) may be used. Look vertically through the glass at the horizontal white

paper, and observe a pale red tint. Attach a small black square to the centre of

the vertical arm at B, the image of this square is seen at h as a deep red image.

Place a similar black square on the horizontal board at C, it should appear

grey ; but a grey on a red ground causes

contrast, and so one sees a grt-enish-blue

S(juare alongside a red one. /^^^H S" ^ ///[■

6. Hering's Apparatus for Simultaneous
Contrast.

(«. ) By means of one or two doubly
refractive prisms (fig. 280, P, P) a double
image is obtained of narrow stri})s of
coloured paper placed eilhei- on a white or
a coloured background. If blue be placed
on yellow, the double image is bluish, and
if yellow be ])laced on blue, the double
image is yellowish {P^flmjer^s Archiv, vol.

47, P- 237).

(/'.) The apparatus of Hering (fig. 281)
is also useful for simultaneous contrast.
Coloure i glasses (''.</., blue and red) are
placed in P and P', and light is refiected
through them by the adjustable white
surfaces (W, W). On looking at a narrow-
black strip (S) oil a white ground, one sees
contrast phenomena according to the colours of the glass used.

The white surface in front of the red glass, when looked at with one eye, is
red, just as that in front of the blue glass is blue \inder the same conditions.
Focus the eyes for an object nearer than the black strip on the white ground.

-Hering's Apparatus for
Contrast.

FlO. 280. — Hering's Apparatus for siimiltiuieous
Contra.->t witli Binocular Vi.'^ion l>v two
D.)ub v Refractive Prisms, P, P. G. Gla.ss
to avoid reflection.

Fig. 281.— Hering's Apparatus for Simultaneous Con-
trast. P, P'. Coloured glasses: H', H". White
reflectors: .*?. Black line on white surface.

This is done by looking at a bead {k) fixed on the point of a rod (supplied
with the instrument), the latter being held between the eyes and the white
ground. The black strip seen under these conditions forms a double image,
i.e, its image is formed on two non-corresponding parts of the retina. The

358 PRACTICAL PHYSIOLOGY, [lXXIV.

two images are in strong contrast, while the two surrounding areas scarcely
contrast at all. (Hering's api»aratus is made by Rothe, Wenzelbad, Prague.)

There are two theories of contrast, viz., that of Helmholtz, the
"psychological theory," and the "physiological theory," of which
Hering is the chief supporter. Hering has devised many experiments
in support of liis contention. The former theory represents contrast
as due to an error of judgment. On the physiological theory, Hering
supposes that there are material chemical changes in a hypothetical
retino-cerebral "vision-stuff" (" Seh-stoff'"). These changes may
be assimilative (anabolic) (black, blue, green), or dissimilative
(katabolic) (white, yellow, red). A change in one area may
influence the retino-cerebral apparatus outside the area directly
affected by the stimulus.

7. Hering's Experiment on Simultaneous Contrast.

Divide a large (|uadrilateral sheet of paper vertically into halves,
and make one half black and the other white. Near the centre of
the vertical division gum two V-shaped pieces of grey paper (one
on the black and the other on the white half) with their apices
together. The V on the black looks lighter by contrast than that
on the white. Fix the V's for a minute, and then look at a uniform
surface. Even after the after-image of the back grounds has
disappeared, the after-image of the V on the black ground looks
darker than that of the V on the light ground. This, Hering con-
tends, must be due to a material change taking place in a localised
part of the retino-cerebral apparatus. It seems difficult to explain
this result as dependent upon an error of judgment due to the
influence of the background. Hering regards this as a fundamental
experiment in support of his theory. Similar experiments may be
made with coloured papers.

8. Successive Light Induction {Herivg).

{a.) Look for one minute at a small white circular disc on a black back-
ground, e.g., velvet. Close and cover the eyes. A negative after-image of
the disc appears, but it is darker and blacker than the visual area, and it has
a peculiar light area round it, brightest close to the disc, and fading away
from it.

{b.) Look at two small white squ.ire patches of {)aper placed one-eighth of
an inch apart on a black background. On closing the eyes, the black space
between them looks brighter than the other three sides of the squares.

(c. ) Look at a black strip on a white ground. On closing the eyes there is
no partial darkening of the white ground, but only an intensely bright image
of the strij'.

9. Coloured Shadows.

{n.) Place an opaque vertical rod fl inch in diam. ) in front of a white back-
ground. Admit not too bright daylight to cast a shadow of the rod. Place
a lighted candle behind one side of the rod, the shadow caused by the yellow-

LXXIV.] CONTRAST. 359

red light of a candle, and illuniiiiated by the daylight, appears blue, i.e., a
purely subjective blue, the complementary colour of the yellow-red light of
the candle, which casts a yellow light. The ettect is more pronounced the
darker both shadows aie. To show that the blue is j)urely subjective, roll up
a sheet of black paper— black surface innermost — in the form of a tube about
} inch or less in diameter. At a distance of i8 inches look at the centre of
the blue shadow, and let an observer cut off the light from the candle by
means of an opaque screen. On removing the screen no change is visible,
but if the tube be directed to the line of junction of the blue shadow, with
the illuminated background just beyond it, the blue appears.

{b.) In a window-shutter of a dark room cut two square holes (lo cm.) on
the same horizontal j)lane, and 2 feet apart. In one fix a piece of clear glass
to admit ordinary white light, and into the other fit a red or green coloured
glass. Botii openings must be provided with a movable shutter to regulate
the amount of light admitted. At 3-4 feet distance place a rod or flat piece
of wood vertically against a white surface. Observe two shadows. Suppose
the glass to be red, then the shadow due to the ordinary light is red, that of
the red glass is greenish. Substitute for the red light that of a lighted candle.
The shadow then appears blue.

10, Choroidal Illumination.

(«.) In a dark room light an ordinary lamp or fan-tailed gas-burner. Place
the source of light at the right side, about 2 feet from an open book or sheet
of paper. Partly separate the fingers of the left hand and place them over the
face, so that different portions of the paper are seen by each eye. That half of
the page seen with the right eye has a greenish tint, the other part seen
with the left eye is red or pinkish. Change the source of light to the left side,
the colours are reversed.

{!).) With the conditions as in (a.), hold a piece of paper (3-4 cm. wide), era
visiting-card, between the eyes with its flat surface towards the face, the same
phenomena are seen

(c. ) Cut in a piece of black cardboard two rectangular holes (4 x 10 mm.),
separated by a distance about equal to that between the pupils, with the con-
ditions as in {11.}. Hold the cardboard about 10 inches or more from you,
and look through the holes at a white surface ; four images of the two holes
will be seen ; the inner right and outer left images are impressions from the
right eye, the inner left and outer right from the left eye. This is easily
proved by closing either eye, when the images belonging to that eye disappear.
If the source of light be on the right side, the former pair of images is greenish
in colour, the latter is pale pink. Change the light to the left side and the
colours are reversed ( //. Sewall). The colour-phenomena occur without the aid
of objective colour, and are due to light passing through the sclerotic and
choroid coats.

11. Binocular Contrast.

Place a white strip of paper on a black surface, look at the white j)aper
and squint so as to get a double image. In front of the right eye hold a blue
glass, and in front of the left one a grey (smoked) glass. The image of the
right eye will be blue, that of the left yellow. Instead of the grey glass, a
card with a small hole in it placed in front of the left eye does perfectly well.
The yellow of the left eye is a contrast sensation.

12, Positive Afterimages.

(a.) In a room, not too brightly illuminated, rest the retina by
closing the eyes for a minute. Suddenly look for two seconds at a

360 PRACTICAL PHYSIOLOGY. [lXXIV.

gas-jet surrounded with a white globe, then close the eyes. An
image corresponding to that looked at will be seen.

{b.) Rest the retina by closing the eyes, tlien look at a gas-
flame surrounded with a coloured glass, or look at a gas-flame in
which some substance is burned to give a characteristic flame, e.g.,
common salt. Then look at a white surface, when a positive after-
image of the same colour will be seen. In all these cases the
image moves as the eye is moved, showing that we have to do with
a condition witliin the eye.

13. Negative After-images. These are regarded as a sign of
retiuo-cerebral fatigue. — Successive Contrast.

(a.) Rest tlie retina, and then stare steadily for half a minute or
less at a small white square or white cross on a black ground. To
ensure fixation of the eyeballs, make a small mark in the centre of
the white paper, and fix this steadily. Then suddenly slip a sheet
of white paper over the whole, a black square or cross will appear
on the wliite background. I find that the best black surface to use
is the dull black of the " Tuch-papier," such as is used by opticians
for lining optical apparatus. Notice also while staring at the white
paper that its margins appear much brighter than the centre, owing
to contrast.

{b.) The black negative after-image may also be seen by closing
the eyes.

(c.) Look at a black square or cross on a white ground. Turn
to a grey surface, when a white square or cross will appear.

{(i.) Stare intensely at a bright red square on a black surface
for twenty seconds, and then look at a white surface : a bluish-
green patch on the white is seen. It waxes and wanes, and finally
vanishes.

(e.) A green stared at in the same way gives a red, i.e., in each
case the complementary colour is obtained as a " negative coloured
after-image."

(./'.) Place a small red and a small green square side by side on
a black background, stare at them, and quickly cover the whole
with a sheet of white paper : a greenish-blue after-image will appear
in place of the red, and a reddish-purple instead of the green.

Tliese negative after-images are examples of so-called " Succes-
sive Contrast."

14. Haploscope (dTrXoos — single).

Place the eyeballs in the primary position, i.e., look straight
ahead at a hypothetical object on a level with the eyes, but placed
at the horizon. The visual axes are parallel, and we have two
distinct and separate fields of vision. On looking through two

LXXIV.]

STEREOSCOPE.

361

Fig. 282. — To illustrate Haploscopic Vision.

parallel tubes placed one in front of each eye, one obtains two
different retinal pictures. Nevertheless, single vision is the result,
and the two different pictures are combined to give an illusory
sensation of one object. One gets approximately haploscopic vision
with a stereoscope.

Haploscopic vision may be illustrated by vertical lines, parts of
circles (Heriug, Hermann's Handbuch d. Physiologie, iii. p. 355),
or by tlie familiar bird
and cage experiment (fig.
282). Hold the figure
close to the eyes, separate
the two fields of vision
by a card held vertically
in the mesial plane be-
tween the eyes, and look
beyond the picture, i.e.,
allow the eyeballs gradu-
ally to diverge from the point of convergence. On doing so, as
the visual axes become less convergent, one has on the right visual
field a bird, on the left a cage, — the bird appears to move into the
cage, and in consciousness we have the illusion as if the bird were
in the cage.

15. Stereoscope.

(a.) Examine a series of stereoscopic slides to show the combina-
tion of the images obtained by the right and left eyes respectively.

{}).) Struggle of the Fields of Vision. — Place in a stereoscope
a slide of glass Avith vertical Hues ruled on one half of it and hori-
zontal lines on the other half. Look at the two dissimilar images ;
note that tliey are not combined, but sometimes one sees it may be
only the horizontal, at another only the vertical lines. It may be
done also with coloured slides.

{c.) Lustre. — Use a stereoscopic sUde, preferably a geometrical
pattern, e.g., a crystal where tlie boundary-lines are white and the
surfaces black. iSuch a slide shows glance or lustre.

16. Lustre in Coloured Objects.

This may be sliown by looking at a _<,'reen patch (electric green) on a red
ground through coloured glass, e.g., a blue glass before one eye and a red one
before the other eye. Other combinations may be made,

17. Stereoscopy Dependent on Differences of Colour.

{n. ) Difference of colour may be the cause of an apparent difference in
distance. If one looks from a distance of 3 metres at red and blue letters
(8x4 cm.) on a black background, to most observers the red appears nearer
than the blue. It is usual to explain this by difference of accommodation,
more effort being required to focus for the red letters than for the blue ; and

362 PRACTICAL PHYSIOLOGY. [LXXIV.

hence the red is regarded as nearer. This is not a sufficient explanation, as
many see the blue nearer than the red. The apparent difference disappears
on closure of one eye, but on opening the other eye, the difference of distance
asserts itself. Is this due to stereoscopy ? Einthoven supposes that it is.
(Einthoven, " On the Production of Shadow and Perspective Effects by Difference
of Colour," i/ram, 1893, p. 191.)

(b.) Briicke showed that the retinalimages of differently coloured points
are shifted with respect to one another. Yik on a black background a narrow
vertical strip of pa})er, the upper and lower thirds being red and the middle
third blue. On looking at the strip with one eye the blue part deviates to
one side and the red to the other side. '" By covering either eye alternately
a deviation of the red and blue parts in o{)posite directions will be observed ;
and on both eyes being used, the notion of a difference in distance is proved
by the combination of the two images in such a way that the parts that
deviate to the nasal side constitute the nearer image, the parts that deviate
to the temj)oral side, the further image." Einthoven finds that the stereo-
scopic effect is more marked with the coloured letters.

(c.) The relative removal of the differently coloured images is due to the
excentricity of the pupil. The pupils may be made highly excentric by
covering them partially. With a nasal excentric pupil {i.e., covered on the
temporal side) a shifting of the differently coloured images in one direction
will be observed ; with a temporal excentric pupil {i.e., nasal side covered)
the shifting will be in the other direction.

Let any one who sees the red letters before the blue "cover his pupils
symmetrically on the temporal side, the red letters retreat and soon appear to
be behind the blue. On covering the pupils symmetrically on the nasal side,
the red letters come forward more and more."

The bearing of these experiments is fully discussed by Einthoven in the paper
already referred to.

17. Benham's Spectrum Top.

{n. ) A cardboard circular disc, about 4 inches in diameter, is made with one
half black and the other half white. On the white are a number of arcs of
concentric circles of dilierent radius. On rotating this disc, coloured lines are
seen whose order is reversed when the disc is made to rotate in an opposite
direction. The experiment is best performed by artificial light.

{b.) Modification by Hurst.

On a circular disc, 4 or 5 inches in diameter, half white and half black,
draw in black on the white half and in white on the black half arcs of various
lengths and thicknesses, as, for instance, the arcs shown in fig. 283. Mount
the disc on a peg and spin it. The arcs appear as circles of various colours,
the colour of each depending on its position and length, on the velocity of
rotation, and on the kind and intensity of illumination. The two outermost
lines on the disc figured when the disc is turned to the left and seen in very
Ijright lamp-light appear purple-grey, becoming, as the rotation becomes
slower, brighter and redder, and then in succession bright crimson, scarlet,
and orange-vermilion. By very bright direct sunlight the earlier shades are
brighter than the later ones, the colour being at first usually a very pure blue.
When the disc is turned to the right, the colours are in succession dark green,
indigo fringed with pale blue, black, by lam)>light, while by bright sunlight
the colour is first dull red, then brown, and finally dark blue. They appear,
however, very different to different observers.

The colours of the white lines are almost entirely yellow, orange-pink, puce,
and "electric blue."

If, instead of arcs of circles, a sj)iral-line is drawn as in fig. 284, the disc
exhibits, when spun at a suitable speed, a broad band of colour, consisting of

LXXIV.]

SPECTRUM TOP.

363

a complete series of all the colours of the spectrum in their normal order, red
being on the outer and violet on the inner side of the band when the disc is
turned to the left, and in the reverse order when it is turned to the right.
Tlie purity of the colours seen depends very greatly on the light used. With
bright daylight no trace of a spectrum is seen, but a series of colours ranging
from purple through brown to green, or other series according to intensity of
light and velocity of rotation. Even under the best conditions, namely,
bright lamp-liglit, slow rotation, and the eyes too fatigued to follow the line
round or sutficiently practised to remain motionless, the colours are not all
brightest at the same moment. The violet has merged into black before the
rotation has become slow enough to give the brightest red and orange.

Beyond the limits of the spectrum-coloured band are two fringes, a purj)Ie
or violet one beyond the red, and luminous pale blue on the violet side. These

Fias. 283 and 284. — Modifications of Discs for Benham's Spectrum Top {Uurst).

ft'inges, as well as the spectral band, change somewhat in colour as the speed of
rotation changes.

The spiral is most easily drawn with a brush full of black paint, by draw-
ing it lightly across a rotating while disc while the disc is spinning. A suit-
able j)ortion of the curve is chosen and tire other half of the disc is blacked.
Dull black paint, such as water-colour " lamp-black," is best.

A very diflerent colour-band is produced by a similarly shaped spiral curve
of white drawn on the black half of the disc. The colours are " electric " blue,
pink, yellow, the blue being outermost when the disc is spun to the lefL
Spirals of various ' pitches " may be used, the line itself being not more than
one-fifth of the breadth of the space between two successive turns of the spiral.
— {Cominunkated hij C. llcrhcrt Hurxt, Ph.D.)

The appearances presented when the tojjsare viewed in monochromatic light
are quite as surprising as those described above (see Abney, Xalure, vol. 51,
p. 292, 1895).

18. Anaglyph.

The pictures of one object are printed on one card in different colours, say
pale red and blue. The two pictures are slightly displaced relative to each
other. On looking at tlie picture through a blue and a red glass, i.e., a blue
glass iu front of one eye, and a red one in front of the other, one sees a nearly
colourless object, but the whole is stereoscopic.

364 PRACTICAL PHYSIOLOGY. [LXXV.

LESSON LXXV.

OPHTHALMOSCOPE— INTRAOCULAR PRESSURE—
FICK'S OPHTHALMOTONOMETER.

The Ophthalmoscope. — Two methods are employed, and the
student must familiarise himself with both, by examining the eye of
another person, or that of a rabbit, or an artificial eye.

1. Direct — giving an upright image.

2. Indirect — giving an inverted image.

A. Human Eye. — (i.) Dii'ect Method.

(a.) About twenty minutes before the examination is commenced,
instil a drop of solution of sulphate of atropine (2 grains to the
ounce of water) into, say, the right eye of a person with normal
vision. The pupil is dilated and accommodation for near objects
is paralysed, owing to the paralysis of the ciliary muscle. The
patient is seated in a darkened room, and the observer seats himself
in front of him, and on a slightly higher level. Place a brilliant
light, obscured everywhere except in front, on a level with the left
eye of the patient.

(h.) The observer takes the ophthalmoscope mirror in his right
hand, resting its upper edge upon his eyebrow, holds it in front of
his own eye, looking through the central hole in it, and directs a
beam of light into the observed eye, when a red glare — the reflex
— is observed. The patient is told to look upwards and inwards,
which is conveniently accomplished by telling him to look to the
little finger of the operator's riglit hand. The operator then
moves the mirror, with his eye still l)ehind it, and looks through
the hole until the mirror is within two to three inches from the
observed eye, taking care all the time that the beam of light is
kept steadily thrown into the eye. If the eyes of the observer
and patient be normal, the observer has simply to relax his
accommodation, i.e., look as it were at a distant object, when the
retina comes into view as an erect or upright object.

(c.) Observe the ntinal blood-vessels running in different direc-
tions on a red ground. Move the mirror about to find the optic
disr, with the central artery emerging from it. Trace the course
of the veins accompanying the arteries across the disc.

(2.) The Indirect Method, giving an inverted image.

(a.) The patient, the light, and the observer are as before.

£

LXXV.] OPHTHALMOSCOPE. 365

The observer places himself ahoiit 20 to 18 inches from the patient,
and, holding the mirror in his right hand, by means of it throws
a beam of light into the eye of the patient. When the eye is
illuminated, he takes a small biconvex lens of 2 to 3 inches focus
in his unemployed hand — the left in this case — holding it between
his thumb and index-finger, placing it vertically 2 or 3 inches from
the observed eye. To ensure that the lens is held steadily, rest the
little finger upon the temple or forehead of the patient. Keep the
lens steady, and move the mirror until the optic disc is seen, with
the details already described.

In the direct method only a small part of the retina is seen at
one time, but it is considerably magnified ; while by the indirect
method, although more of the retina is seen at once, it is magni-
fied only slightly.

If the observed or observer's eye is abnormal, suitable glasses to
be fixed behind the mirror are supplied with every ophthalmoscope.
In some forms of ophthalmoscope,
such as that of Gowers and others,
these lenses (convex + , and con-
cave — ) are fixed to a rotating
disc behind the mirror. As the
disc is rotated, lens after lens can
be brought to lie exactly behind
the hole in the mirror, and thus
correct any anomaly of refraction.

3. Eye of a Living Rabbit. Fig. 285— carriage for Rabbit.

Instil atropine as before, or
use an atropinised gelatine disc to effect the same result. Place
the rabbit in a suitable cage to keep it from moving. A suitable
one was devised by Michel ; use it (fig. 285). Examine the eye by
the direct and indirect methods. N.B. — If an albino rabbit be
used the observer sees the large choroidal vessels.

4. Perrin's Artificial Eye.

Use this until a clear image of the fundus is obtained by both methods.
In fact, it is well for the student to begin with this. In this model, eye-caj)s
to fit on to the eye are suj)j)lied. so as to render the eye-model eitlier myopic
or hypermetropic. Afterwards test these, and use the necessary lenses behind
the mirror to correct these errors in the shape of the eyeball.

Fro-st's artificial eye, as made by Curry and Paxtou, is also useful, as is also
that of Priestley Smith.

5. KUhne's Method. — If an artificial eye is not at hand, a very
suitable arrangement is that devised by Kiihne. Paint a disc to
resemble the normal fundus when it is seen with the ophthalmo-

366

PRACTICAL PHYSIOLOGY.

[lxxv.

scope. Remove the eye-piece — long one — from an ordinary micro-
scope. Screw out the lower lens of the eye-piece, fix in the painted
disc, and block up the lower aperture with a piece of cork. Fix
the eye-piece in a suitable holder, and use it instead of an eye to be
examined.

6. Demonstrating Ophthahnoscope {Priestley Smith).

The general arrangement of this instrument is shown in fig. 286. At one
end of the horizontal bar is a chin support for the patient ; at the other a
perforated glass mirror, capable of steady adjustment to any position. The
transverse arm near to the mirror carries a candle, provided with a light metal
screen on either side of it ; one of these hides the candle from the patient, the
other hides it h-om the observer, and enables him at any moment to cut off
the light from the mirror, and thus to protect the patient's eye from unneces-

FiG. 286. -Denioustrating Ophthalmoscope. Made by Pickard and Curry. Cost, £3, 10s.

sary illumination without disturbing the adjustment of the instrument. A
wire placed in the pillar of the mirror, and movable to either side, carries a
piece of white paper, which serves as a fixation point for the patient's eye.
At the middle point of the horizontal bar is a jointed support carrying a light
rod, one end of which is held in the hand of the observer, while the other holds
the lens. By means of this rod the observer can place the lens in any desired
position in relation to the patient's eye.

(i.) Arrange the instrument as in fig. 286.

(2.) Adjust the patient's seat so as to bring his chin comfortably on the
sujiport ; let him rest his arms u])on the table.

(3.) Place the rod quite horizontal, and then raise or lower the centra]
support until the centre of the lens is on a level with the patient's pu[)il.

(4.) Push the lens to one side and adjust the mirror so as to throw the light

LXXVI.] TOUCH, SMELL, TASTE, HEARING. 367

upon tlie patient's eye, telling him to look, not at the mirror, but at the paper
placed upon the wire. The paper must be on the opposite side to the eye.

(5.) Take the rod in the hand and adjust the position of the lens so as to
bring the optic disc into view.

(6.) In changing places with another observer, cut oflF the light from the
mirror by means of the candle-screen.

7. Intraocular Pressure. — Fick's Ophthalmotonometer,

This instrument is extensively used in German eye-hospitals, and consists of
a small brass plate (6 mm. diameter), which is attached by means of a metallic
spring to a base, which also carries a scale which indicates the amount of
pressure applied. One presses the disc of the instrument against the eyeball
until it flattens the part to which it is applied, when the pressure is read off
in grammes. The experiment may be done first on a rabbit, as most of them
remain quite ])assive. Place a person with his left shoulder next the window,
ask him to turn his eyeballs to the right and open his eyelids, whereby
sufficient of the eyeball is made visible for the application of the instrument.

8. The Pupil. — Normally the pupil in man, rabbits, and other animals is
black, but in albinos it is reddish. Why ?

( I. ) Select an albino rabbit, and exactly in front of its pupil hold up a black
card with a hole in it the size of the pupil. Direct the pupil to the light, and
arrange the shade so that all light is kept from the eye except that which
enters it by the pupil. The albino pupil then appears black.

This shows that the blackness of the pupils is not due to the light
entering the eyeball being absorbed by the pigment of the fundus of the eye,
but that light entering the eye can only emei'ge by the pupil when the iris and
the neighbouring parts of the choroid, in virtue of their jiigmentation, do not
permit light to pass through them. The construction of the dioptric apparatus
of the eye is such that light from the fundus of the eye must be reflected back
to the source from which it came, i.e., to the focus. As we emit no light from
our eye none can come to us from the observed eye, so we see the pupil black
because we do not illuminate the fundus with our body {Schciik).

LESSON LXXVI.
TOUCH— SMELL— TASTE— HEARING.

1. Touch— The Sense of Locality.

(a.) Ask a person to sliiit liis eyes, touch some part of his body
Avith a pin, and ask him to indicate the part touched.

(h.) JEsthesiometer. — Use a small pair of wooden compasses,
or an ordinary pair of dividers witli their point.s guarded by a
small piece of cork, or Sieveking's .SJsthesiometer. Apply lightly
the points of the compasses simultaneously to different parts of
the body, and ascertain at what distance ajjart the points are felt
as two. The following is the order of sensibility :— Tip of tongue

368

PRACTICAL PHYSIOLOGY.

[LXXVL

(i.i mm.), tip of the middle finger (2.3), palm (8 to 9), forehead
(22), back of hand (31.6), back (66).

(c.) Test as in (/a) the skin of the arm, beginning at the shoulder
and passing downwards. Observe that the sensibihty is greater as
one tests towards the fingers, and also in the transverse than in the
long axis of the limb. In all cases compare the results obtained on
both sides of the body.

(d.) By means of a spray-producer spray the back of the hand with ether,
and observe how the sensibility is abolished.

(c. ) V. Fray's Method.— A hair of the head or beard (20-40 mm. long) is
fixed to a wooden match. On pressing the point of the hair against the skin
it may or may not be felt as a tactile sensation. This depends on the pressure
exerted on the hair, and this in turn on the sectional area and stiffness of the
hair itself. One can measure the pressure exerted by pressing the hair on a
balance and from the sectional area of the hair deduce the pressure per sq.
mm. According to v. Frey the sensibility of the coi'nea and conjunctiva is
distributed in a punctiform manner, insensible areas existing between : pain
alone, according to v. Frey, being experienced from stimulation of the cornea
with the exception of its margin and the teeth, or rather the dentine and pulp.
(V. Frey, " Beitrage z. Physiologic d. Schmerzsinns," and "Beit. z. Sinnes-
physiologie d. Haut," Bench, a. d. math.-phys. Glasse d. Koniql. Sachs.
Gesell. d. Wisscn. Leipzig, Dec. 1894, and March 1895. Criticism by Nagel,
Pfliiger's Archiv, Bd. 59, p. 563, 1895.)

(J.) Illusions — Aristotle's Experiment.- — Cross the middle over
the index-finger, as in fig. 287, roll a small ball between the
fingers ; one has a distinct impression of two
balls. Or, cross the fingers in the same way,
and rub them against tlie point of the nose.
The same illusion is experienced.

2. The Sense of Temperature.

(a.) Ask the person experimented on to
close his eyes. Use two test-tubes, one fiUed
with cold and the other with hot water, or
two spoons, one hot and one cold. Apply one
or other to different parts of the surface, and
ask the person to say whether the touching
body is hot or cold. Test roughly the sensi-
l)ility of different parts of the body with cold
and warm metallic-pointed rods.
{h.) Touch fur, wood, and metal. The metal feels coldest,
although all the objects are at the same temperature.

(r.) Plunge the hand into water at 36° C. One experiences a feeling of heat.
Then plu7ige it into water at 30° C. , at first it feels cold, because heat is
abstracted from the hand. Plunge the other hand direct into water at
30" C. without previously placing it in water at 36° C, it will feel pleasantly
warm.

Fig. 287.

LXXVI.] TOUCH, SMELL, TASTE, HEARING. 369

(d.) Hold one hand for a time in water at 10° C, and afterwards place it
in water at 20° C, at first the latter causes a sensation of beat, which soon
gives place to that of cold.

(e.) Test with the finger the acuteness of the sense of temperature, i.e., in
two given fluids of dilferent temperatures, what fraction of a degree C. can be
distinguished. One can usually distinguish f°, although the acuteness is
greater when the fluids are about 30' C.

(/". ) Use two brass tubes (5 cm. long and i cm. in diam.), terminating in a
point. Cover both, all except the point, with india-rubber tubing. Fill one
with warm water and the other with cold. Test the position of the warm and
cold points on another person on various parts of the skin.

{(/.) Warm and Cold Spots.

With a blunt metallic point touch different parts of the skin.
Certain points excite the sensation of warmtli, others of cold,
although the temperatures of the skin and the instrument remain
constant. Map the position of the cold and hot spots by means of
different colours.

3. Sense of Pressm-e.

(a.) Rest the back of the hand on a table, cover a small area of
the jialm ^yith a non-conducting material, e.r/., a wooden disc. On
the latter place different weights. Estimate the smallest difference
of weight which can be appreciated.

{b.) Dip the hand or a finger into mercury. The greatest sensation is felt
at the plane of the fluid in the form of a ring, but even this is best felt on
moving the hand up and down.

4. Peripheral Projection.

(a.) Press the ulnar nerve at the elbow, the prickling feeling is
referred to the skin on the ulnar side of the hand.

(6.) Dip the elbow in ice-cold water ; at first one feels the sensation of cold
owing to the effect on the cutaneous nerve-endings. Afterwards, when the
trunk of the ulnar nerve is affected, the i)ain is felt in the skin of the ulnar
side of the hand where the nerve terminates.

5. Reference of Tactile Impressions to the Exterior. — Gene-
rally speaking, the sensation of touch is referred to our cutaneous
surfaces. In certain cases, however, it is referred even beyond
this.

(a.) Holding firmly in one hand a cane or a pencil, touch an
object therewith ; the sensation is referred to the extremity of the
cane or pencil.

(b.) If, however, the cane or pencil be held loosely in one's liand,
one experiences two sensations, one corresponding to the object
touched, and the other due to the contact of the rod with the skin.
The process of mastication afllbrds a good example of the reference
of sensations to and beyond tlie periphery of the body.

2 A

370 PRACTICAL PHYSIOLOGY, [lXXVL

6. Sense of Contact.

Touch your foreheatl with your forefinger, the finger appears
to feel the contact ; but on rubbing the forefinger, or any other
digit, rapidly over the forehead, it is the latter which is interpreted
as " feeling " the finger.

7. Weber's Circles.

Cut short lengths from glass tubing of various sizes, varying from
a quarter of an inch to two inches or more in diameter, and provide
glass vessels of similar size, each with a glass base. Press the
smaller circles and corresponding size of vessel on the cheek and
forehead and the larger ones on the thorax or abdomen. It is
impossible when the eyes are shut to determine whether a closed
or open vessel is pressed on the skin. The size of the vessel to
obtain this result varies with the cutaneous surface experimented

8. Illusions.

(n..) Place a thin disc of cold lead the size of a florin on the forehead of a
person whose eyes are closed, remove the disc, and on the same spot place
two warm discs of equal size. The person will judge the latter to be about
tlie same weight, or lighter, than the single cold disc.

{/>.) Comjjare two similar wooden discs, and let the diameter of one be
slightly greater than that of the other. Heat the smaller one to over 50° C,
and it will be judged heavier than the larger cold one.

(f. ) Lay on different parts of the skin a small square piece of paper with a
small central hole in it. Let the person close his eyes, while another person
gently touches the uncovered piece of skin with cotton wool, or brings near it
a hot body. In each case ask the observed person to distinguish between
them. He will always succeed on the volar side of the hand, but occasionally
fail on tlie dorsal surface of the hand, the extensor surface of the arm, and
very frequently on the skin of the back.

((/.) Estimation of the distance of two neighbouring parts depends on the
size of the sensory circles. If the points of a pair of com|)asses about i cm.
ajiart are placed on the skin in front of the ear and moved towards the lips,
the points feel as if they diverged.

9. The Muscular Sense.

(a.) With the arm and hand unsupported, the eyelids closed, and the same
precautions as in 3 («.), determine the smallest difference which can be per-
ceived between two weights. It will be less than in cartridges filled with a
known weight of sliot, and tested by the pressure-sense alone. The cartridges,
('.(/., 100 grins., are numbered, and they are so made as to have a small increas-
ing increment of weight. They are alike in external ap])earance.

(b.) Take two equal iron or lead weights, heat one and leave the other cold.
The cold one will fuel the heavier.

10. Taste and Smell.— Prepare a strong solution of sulphate of
quinine, with the aid of a little sulphuric acid to dissolve it (bitter),

LXXVI.] TOUCH, SMELL, TASTE, HEARING. 37 1

a 5 per cent, solution of sugar {sired), a lo per cent, solution of
common salt (m/ine), and a i per cent, solution of acetic acid
(acid).

(a.) Wipe the tongue drj^ lay on its tip a crystal of sugar. It
is not tasted until it is dissolved.

{f>.) Apply a crystal of sugar to the tip and another to the back
of the tongue. The sweet taste is more pronounced at the tip.

{('.) Repeat the pi-ocess with sulphate of quinine in solution. It
is scarcely tasted on the tip, Init is tasted immediately on the back
part of the tongue.

('/.) Test where salines and acids are tasted most acutely.

(e.) Connect two zinc terminals with a large Grove's battery, aj)j)ly them to
the upper and under surface of the tongue, and pass a constant current through
the tongue. An acid taste will be felt at the positive, and an alkaline one at
the negative pole.

(/. ) Close the nostrils, shut the eyes, and attempt to distinguish by taste
alone between an ap}ile and a potato.

(</.) Gymnema Sylvestre. — Use a 5 p.c. decoction of the leaves and apply
it to limited areas of the tongue by means of a camel-hair jiencil. In 20-30
seconds wash out the mouth and then test the action of glycerin (5-10 p.c),
quinine (i p.c. with .01 p.c. of H^SOj', H0SO4 (.05 p.c.'), NaCl (.5 p.c).

The sweet and bitter tastes are readily prevented in all regions ; but acid
and saline tastes are not influenced (L. E. Shore, "A Contribution to our
Knowledge of Taste Sensations, " Journ , of Phys. , xiii. p. 191). It has no effect
on tactile sensations.

11. Ear. Hearing.

(a.) Hold a ticking watch between your teeth, or touch the
upper incisors with a vibrating tuning-fork, close both ears, and
observe that the ticking is heard louder. Unstop one ear, and
observe that the ticking is heard loudest in the stopped ear.

(J).) Hold a vibrating tuning-fork on the incisor teeth until you
cannot hear it sounding. Close one or both ears and you will hear
it.

{c.) Listen to a ticking watch or a tuning-fork kept vibrating
electrically. Close the mouth and nostrils, and take either a deep
inspiration or deep expiration so as to alter the tension of the air
in the tympanum ; in both cases the sound is diminished.

(</.) Connect two telephones in circuit with a vibrating Xeef's
hammer of an induction machine, and place a telephone to each
ear ; one hears the sound as if it came from within one's own head
in the vertical median plane.

{e.) With a blindfolded person test his sense of the direction of
sound, e.g., by clicking two coins together. It is very imperfect.
Let a person press both auricles against the side of the head, and
hold both hands vertically in front of each meatus. On a person

372 PRACTICAL PHYSIOLOGY, [LXXVL

making a sound in front, the observed person will refer it to a
position behind him.

(/) Test the highest audible sound by means of Galton's
whistle.

12. Dissection of the Middle Ear. — It is most important for the
student to do this. Use the head of a sheep. Remove the lower
jaw, expose the temporal bulla. Open this and thus reach the
tympanic cavity, when the various structures situated in the
middle ear are readily brought into view.

13, Influence of Excitation of one Sense-Organ on the other
Sense-Organs. — Urbantschitsch has made a large number of
experiments on this subject.

{a. ) Small coloured patches whose shape aud colour are not distinctly visible
may become so when a tuning-fork is kept vibrating near the ears. In other
individuals the visual impressions are diminished by the same process.

(b.) On listening to the ticking of a watch, the ticking sounds feebler or
stronger on looking at a source of light through glasses of different colours.

(c.) If the finger be placed in cold or warm water tlie temperature appears
to rise when a red glass is held in fi'ont of the eyes.

APPENDIX.

SOME WORKS USEFUL IN THE LABORATORY

R. Gscheidlen, Physiologische Methodik, 1876 (incomplete). — E. Cyon,
Methodik der pliysiologischen Experimente u. Vivisektionen, with Atlas,
1876 (only one part issued). — Ott, The Actions of Medicines, Phil., 1878. —
Claude Bernard and Huette, Precis iconographique de medecine operatoire et
d'anatomie chirurgicale, with 113 plates, 1873 ; also Lecons de physiologie
operatoire (edited by Duval), Paris, 1879. — Sanderson, Foster, Klein, and
Brunton, Handbook for the Physiological Laboratory (Text and Atlas). The
French edition contains additional matter. — Meade-Smith, Trans, of
Hermann's To.xicol. — J. Burdon-Sanderson, Practical Exercises in Physiology,
London, 1882. — Foster and Langley, Pract. Phys., London, 1884. — B. Stewart
and Gee, Pract. Physics. — Vierordt, Anat. Physiol, u. Physik. Daten u.
Tabellen, Jena, 1888.— Muller-Pouillet, Lehrb. d. Physik., 8th ed., Braunsch-
weig.— Wiillner, Lehrb. d. exp. Physik. — Liven, Manuel de Vivisect., Paris,
18S2. — Harris and Power, Manual for the Phys. Lab., 5th ed., 1892. — Strans-
Durckheim, Anat. descrip. comp. du. chat, Paris, 1845. — W. Krause, Die
Anatomic des Kaninchens, Leipzig, 2nd ed., 1883. — A. Ecker, Die Anatomic
des Frosches, 1864-1SS2, and ed., pt. i., 1888. — Biolog. Memoirs, edited by
Burdon-Sanderson. — Helmholtz, Physiol. Optik, 2nd ed. — Hennann, Hand
buch der Physiologie (by various authors). — Gad, Real-Lexikon d. Med. Pro-
piideutik, Wien, 1893 (not yet completed). — L. Fredericq, Manipulations de
Physiologie, 1892. — LangendorfF, Physiol. Graphik. — Gotch, Practical Exer-
cises in Physiology. — Halliburton, Syllabus of Exjierimental Lessons, 1893. —
Schenck, Physiologisches Practicum, Stuttgart, 1895. — W. Biedermann,
Elektrophysiologie, .Jena, 1895 (^ most useful work, chiefly dealing witii
Muscle and Nerve). — Richet, Dictionnaire de Physiologie, vol. i., Paris, 1S95.

The above list takes no account of the various Physiological Journals.

374 APPENDIX,

n.

SOME WORKS OF REFERENCE OX CHEMICAL
PHYSIOLOGY.

Hoppe-Seyler, Physiologische Clieuiie, Beiliu, 1892-94. — Lehmann,
Lehrb. d. phys. Chem., 3rd edit., Leijtzig, 1853 ; and Handbuch, 1859. — Leo.
Liebermann, Grundziige der Chemie des Menschen, Stuttgart, 1880. — Robin
and Verdeil, Traite de chem. anat. et phys. (with Atlas 'i, Paris, 1853. This
Atlas contains beautiful plates with figures, many coloured, of all the most
imjjortant organic crystalline bodies. — A. Wynter Blyth, Foods, iSSj.—Gorup-
Besanez, Anleitung zur Zoo-chemischen Analyse, 1871. — Gautier, Chimie
applique a la Physiologie, 1874. — Lehmann's Phys. Chem. (translated by
Cavendish Soc, 1851-1854), with Atlas of 0. Funke's plates. These plates
contain some histological figures, and many coloured plates of blood-crystals,
deposits in urine, &c. — Kingzett, Animal Chem., 1878. — Thudichum, Ann. of
Chem. Med., 1879, —A, Gamgee, Physiological Chemistry of the Animal
Body, vol. i., 1880; vol. ii.. Chemistry of Digestion, 1893. — Hoppe-Seyler,
Medicinische Chemische Untersuchungen, Berlin. This contains a number of
special memoirs by the pupils of the author.— Hoppe-Seyler, Zeitschrift fiir
physiologische Chemie, Strassburg, 1877, and continued until the present. —
Watts' Dictionary of Chemistry, second supplement, London, 1875. — Ralfe,
Clinical Chemistry, London, 1880 ; and Clinical Chem., 1 883. ^Wurtz, Traite
de chim. biol., Pari.s, 1880.— Parkes' Hygiene, 7th edit. — T. C. Charles,
Physiological and Pathological Chemistry, London, 1884.- — Maly's Jahresb.
ii. Thierchemie. This gives a resume of the most important memoirs pub-
lished during the year.— Articles in Hermann's Handbuch d. Physiologie,
1879-18S4, and the various Text-books on Organic Chemistry. — Roscoe and
Schorlemmer, (Organic) Chem., 18S4-1889. — Beilstein, Handb. d. organ.
Chem. — Krukenberg, Grundriss d. med. chem. Analyse, 1S84. — MacMunn,
The Si>ectroscope in Medicine, 1880 ; Clinical Chemistry, 1890. — Drechsel,
Anleit. z. Darstell. phys. Chem. Pr.iparate, 18S9. — Ladenburg, Handwiirter-
buch d. Chemie. This consists of special articles, and is on the plan of
Watts' Dictionary of Chemistry. —Kossel, Leitfaden fiir med. chem. Curse,
1889. — Rohmann, Anleitung z. chem. Arbeiten, 1890. — Landolt, Dasoptisches
Drehungsvermiigen is the standard work on polariscopic methods. — MacMunn,
on the Spectroscope. This work has good lithograjjhed and coloured spectra.
— Tollens, Handbuch d. Kohlenhydrate, Breslau, 1883. This is the best work
on the Carbohydrates. — Sutton, Volumetric Analysis. This work gives all
the most important methods for this process. — Bunge, Phys. and Path. Chem.,
trans, by Wooldridge, 1890, 4tli German ed., 1894. — V. Jaksch, Clinical
Diagnosis, trans, by Cagney, 2nded. — Halliburton, Chemical Phys. and Path.,
i8qi. — Hammarsten. Lehrb. d. Physiol. Chem., 2nd ed., Wiesbaden, 1891. —

APPENDIX. 375

S. Lea, The Chemical Basis of the Animal Body, 1892. — Salkowski, Practi-
cum d. phys. u. path. Chemie, Berlin, 1893. — Armand Gautier, Cours de
Chemie ; Chimie Biologique, vol. iii., Paris, 1892. — Hempel, Gas Analyse,
translated by L. M. Dennis. — Neumeister, Lehrb. d. phys. Chem., pt. L,
1892. — Chittenden, Dige.stive Proteolysis, New Haven, Conn., 1895.

The literature on the " Urine " is necessarily very large, and may readily be
obtained on consulting any of the standard works on that subject.

The following are the CHIEF JOURNALS AND PERIODICALS containing
physiological literature.

Proceedings and Transactions of the Royal Society.

Journal of Anatomy and Physiology (Humphry, Turner k M'Kendrick)
from 1868.

The Journal of Physiology (Foster, and presently Langley) since 1878.

Archivfiir Anatomic und Physiologic (Miiller 1834-1858, du Bois-Reymond
from 1859.

Zeitschrift fiir Biologic (Kiihne & Voit from 1865).

Archiv fiir die ge.sammte Physiologic (Pfliiger from 1868).

Archiv fiir path. Anat. und Physiologic (Virchow from 1847).

Archiv fiir exp. Path, und Pharmacologie (Naunyn & Schmiedeberg from

1873)-

Skandinavisches Archiv fiir Physiologic 1 Holmgren from 1889).

Zeitschrift fiir Physiol. Chemie (Hoppe-Seyler from 1877).

Sitzungsberichte der. Acad. d. Wisseuschaften, of Berlin from 1836, of
Vienna from 1848.

Ludwig's Arbeiten Leipzig from 1866-1877 (continued in du Bois Archiv
from 1877).

Comjites rendus de 1' Acad, des Sciences from 1835.

Comptes rendus de la Socii-te de Biologic from 1850.

Berichtc d. dc >tsch. chem. Gesellschaft.

Journal de la Physiologic (Brown-Sequard from 1858- 1863).

Archives de Physiologic (formerly Brown-Sequard, now Bouchard, Chauveaux
& Marey) from J 868.

Journal de I'Anat. et de la Physiol. (Robin, Pouchet, now Mathias Duval)
from 1864.

Archives Italienne&de Biologie (Mosso from 1882),

GENERAL REFERENCES AXD ABSTRACTS.

Schmidt's Jahrbucher (from 1S34). Canstadt's Jahresbericht ; Hoffmann
& Schwalbe's Jahresbericht (from 1873, now by Hermann). Maly's Jahres-
bericht ii. d. Fortschritte d. Thier Chemie (chiefly physiological chemistry).
Hayem, Revue des Sciences medicales. Reports of the Chemical Society.

n^

APPENDIX.

III.

CARBOHYDRATES

-= — 111

■33 — ^tc

Cellulose.

Starch.

Glycogen.

Dextrin.

Cane-Siigar.

Milk-Sugar.

CV2H22O11+H2O.

Maltose.

Ci.,H.,.,Oii H- H.,0.

Dextrose.

OeFij^OsC + H.O].

Lsevulose.

Galactose.

0,FT,A-

Solubility.

Insoluble in water,
dilute acids, ami
alkalies; soluble
in animonio-
oxide of copper.

Swells up in water,
dissolves in
warm water.

Soluble in water,
opalescent.

Readily soluble
in water ; sol-
uble with
difficulty in
strong alcohol.

Relation to

lodo-iodide o!

Potassium

Solution.

After treat-
ment with
H2SO4.
Blue.

Blue.

Brown or port
wine.

Browu.

Uiicoloured

Rotation
WD-

+ 197

+ 211

+ 174-5

+ 66.5

+ 52.53
Birotation.

+ 140
Half-
rotation.

+ 52-74
Birotation.

- 71.4

+ 80.S
Birotation.

APPENDIX.

3;;

{after Tollens).

By Hydrolysis on

Boiling with [ Action of

Dilute Acids. | F'erments.

Arises

Arabinose,

Galactose, and

other bodies.

Dextrose.

No action.

By diastase

into
Dextrin

and
Maltose.

By diastase
slowly into
Dextrose.

Yeast and
Similar Fungi.

No action.

J- No action.

Reducing
Power.

Phenyl-hydrazin
Compounds.

Dextrose and
Lsevulose.

By invertin

Dextrose and

Lsevulose.

After invertin

ferments by

Yeast.

Phenyl-glucosazon.

Dextrose and
Galactose.

By ferment of
Kefyrs, Dex-
trose, and
Galactose.

Ferments

with

Kefyrs.

Dextrose.

By diastase
Dextrose [?].

Fermentation
by Yeast.

Non-fermen-
tation by
Yeast.

}- o --i

M.P.

-Lactosazon 200°

-Maltosazon

206°

-Glycosazon

304/5°

-Laevulosazon

204°

-Galactosazon 193°

378

At>l»ENDlX.

BODIES OP THE

The Aromatic Compounds of the Urine and their

C«H

Tyrosin.

OH
4CH,.CH.NH.,.C00H.

From albumin —

Bj' trypsin.

By putrefaction.

By fusing with KHO.

In urine —

In acute yellow atrophy
of tlie liver and phos-
phorus poisoning.

Phenylamidopropionic
Acid.

CgHs. CHg. CH . NH.^. COOH.

Decomposition of albumin
in seedlings.

Oxjrphenyloxypropionic
Acid.

[Oxyhydroparacumaric
acid.]

OH
6"4CH,.CH.OH.COOH.

C«H.

Phenylpropionic Acid.

CgHs.CHa.CHo.COOH.

Decomposition product of
albumin, oxidised in the
organism to

Benzoic acid.

CgHg.COOH.

which passes into the
urine as

Hippuric acid.
C6H5.CO.NH.CH2.COOH.

In the urine of the rabbit
after feeding with ty-
rosin.

In human urine, after
acute yellow atrophy of
the liver and phospho-
rus poisoning.

Oxyphenylpropionio Acid

[Hydroparacumaric acid.]

*"fi"^CH2.CH.^C00H.

Normal constituent of
urine, decomposition
product of tyrosin.
When given to an ani-
mal, part is excreted
unchanged, part is oxi-
dised to

Paraoxybenzoic acid.

pttOH
'-6"4COOH

which passe.s into the
urine as

Paraoxybenzuric acid.
'^6"*C0.NH.CH.,.C00H.

Phenylamidoacetic Acid.

C6Hg.CH.NH2.COOH.

Yields during putrefac-
tion

Amygdalic acid.
C6H5.CH.OH.COOH.

AffENDlX.

379

AROMATIC SERIES.

Relation to the Decomposition Products of Albumin.

Oxyphenylacetic Acid.

OH
'^CH.,.COOH.

CfiH,

Putrefactive product of
tyrosiu ; normal uri-
nary constituent. When
given to an animal, it
leaves the organism un-
changed.

Phenylacetic Acid.

CgHj.CHo.COOH.

Putrefactive product of
phenylamidopropionic
acid and of allnnnin,
passes into the urine as

Phenaeeturic acid.

C6H..CH2.CO.NH.CH2
COOH.

Parakresol,
P„OH

Putrefactive product of
ty rosin ; occurs in urine
as

Indol.
CH = CH

Obtained from albumin
by putrefac^tion, and
heating with caustic
potash.

In the organism it is oxi-
dised to

Indoxyl.
C(OH) = CH

Passes into the urine as

Indoxylsulphuric acid.
C(0.S03H) = CB

NH-"^

Phenol.

CglTe-OH.

Putrefactive product of
tyrosiu ; occurs in urine
as

C6H5.OSO2OH.

In the organism, it is
partly oxidised into

Pyrocatechin.

^6"*0H

which occurs as a con-
stituent of horses' urine,
partly as an ether
sulpho-compound, and
partly free.

C6H4<^

Skatol.
C(CH3)=CH

NH-^

Putrefactive product of
albunuii, passes into the
urine as

(Skatoxylsulphuric acid).
C(CHo.O.SO.,OH) = CH

C6H4<^

38c APPENDIX.

SOME PRODUCTS OF TRYPTIC PROTEOLYSIS— LYSIN,

LYSATIN.

In Lesson X., 5, Leucin and Tj'rosin" are stated to be products formed by the
action of the tryptic enzyme on proteids. These substances, as well as others,
viz,, aspartic acid and glutamic acid, have long been known as decompobition
])roducts of vegetable proteids, e.g., as cleavage products by boiling w th
dilute acids. Aspartic acid is amido-succinic acid, C00H.CHoCH(NH2).
COOH, and is also a product of pancreatic digestion of fibrin, while glutamic
acid, COOH. C3H5(N Ho). COOH, is amido-pyrotartaric acid. Both acids
belong to the fatty acid series.

Drechsel has recently discovered two new nitrogenous bases — lysin and
lysatinin or lysatin — ]iroducts of the decomposition of proteids {e.g., casein,
gelatin, egg-albumin) when the latter are boiled with HCl and stannous
chloride. These bodies result from the simple hydrolytic cleavage of the proteid
molecule, and it has recently been shown by Hedin that they are also formed
in trypsin-proteolysis.

Lysin, CgHjjN.jOa, is a diamidocaproic acid, and is a representative of the
fatty acid group, and has intimate chemical relationships with leucin.

Lysatinin or Lysatin, CgHjaNjOo. —Its composition is less accurately known,
b"ut it has the composition of a creatin. The special interest which attaches
to this body is that, as a product of trypsin-proteolysis, it can by simple
hydrolytic decomposition break down into urea. Thus trypsin-proteolysis
yields cleavage products, from one or more of which comes the substance lysatin,
which behaves like creatin in this respect, viz., that when boiled with baryta-
water, it yields sarkosin and urea. Thus chemists have found a series of
cleavage products the result of hydrolytic decomj)osition between proteid and
uroa. (Chittenden, iJigestive proteolysis, p. 103, New Haven, 1895. Cartwright
Lectures.)

APPENDIX.

381

XANTHIN" BODIES.

NH-C=N

/ I >

Xanthin. CO C-NH
CsH.N.O.,. \ II

NH - OH

Heteroxanthin.
C«H«N,0.,.

N(CH3)-C=N^

Theobromin. CO

C.H.N.O,

\

C-N(CH3)

NH - CH

N(CH3)-C-N

/ ! >

C-NH

Theophyllin. CO
CVHgN.Oo. \ II

N(CH3)-CH

Paraxanthin.
C-HgNiOa.

N(CH3)-C = N

/ I >^'^

CaflFein. CO C-NlCHj)

CsHioN^O^. \ II

N(CH3) - CH

NH-C=N.

/ I >

Guanin. C==NHC-NIJ
C5H5N5.O. \ II

NH - CH

Adenin.
CgH^N.-OH.

Hypoxanthin.

CgH^N^.O.

Camin.

C^HsN^O.

{Rahmann. )

KELATION OF UREA TO THE CO, DERIVATIVES
AND THE GY-COMPOUNDS.

^_p(OH ^_^(NH2 Q_p,iNH3

0=C^nti ^-^|0H ^-'-'iNHz

)0H
Carbonic Acid.

Carbamic Acid. Urea=Carbainid.

/NH2
C02+2NH3=C0<'

N0-NH4
Carbamate of Aminonia.

3S2 APPENDIX.

heating to 130-140° C. : —

\O-NH4 \NH, \0-NH4 V

On heating to 130-140° C. :-

/NH2 /NH2 /O - NH,

C0<'

sNH,
Carbamate of Ainnionia. Urea. Ammonium Carbonate. Urea.

By heating with strong mineral acids or alkalies : —

,NH2 yO-NH4

<1 „
+ SS = CO ,
NH2 \0-NH4

Urea. Carbonate of Ammonia.

{Kruke.nbefrg.')

CORRECTION FOR TEMPERATURE AND PRESSURE
IN THE HYPOBROMITE METHOD (LESSON XIX.).

Theoretically i gram of urea evolves 372.7 cubic centimetres of N", but in
practice it is found from urine that about 343 cc. are obtained. Sujjpose 25 cc.
of N passes over into the gas-collecting tube, and that the temperature of the
room (<) = 10° C. and the barometric pressure 755 mm. Hg, what is the volume
at standard temperature and pressure ?

Let V be the required volume at 0° C. and 760 mm. Hg ; v be the volume
read off ; P = pressure of 760 mm. Hg ; ■p the barometric pressure of the room ;
T the absolute temperature = -273° ; < = the temperature of the room (in
degrees Centigrade + 273) ; then

VP< = vpll.:v = -^^ and V = "J^^

-.T 25 X 755 X 273
V = ^ '^^ ^ '^ = 23.95 cc.
760 X 283 -^ ^^

Next to urea, uric acid is the most important substance present in urine
which is decomposed by hypobromite of sodium. It yields 47,7 per cent, of
its N. But as the quantity of uric acid present in urine is very small, for
practical purposes it may be neglected.

CORRECTION FOR TEMPERATURE AND PRESSURE OF
THE VOLUME OF A GAS, e.g., THE GASES OF THE
BLOOD.

The volume of a gas must be reduced to the standard pressure, 760 mm. of
mercury, and standard temperature, 0° C, according to the formula : —

760 (i -{at)

APPENDIX:. 383

V==the required volume at standard temperature, 0° C, and 760 mm. Hg.
V^ = the volume at the observed temperature and pressure.
A = the observed pressure.

a = the coefficient of expansion, which is a constant (.003665).
t = the observed temperature.

The formula is obtained as follows : —

With reference to the correction of the given volume for temperature .•

and ioT pressure;

760 (i + at)

Example. — Suppose the volume of gas to be corrected for temperature and
pressure, i.e., V'==30 cc, the observed barometric pressure, i.e., /t = 740 mm.,
and the temperature of the room, i.e., <=I5° C, then the required volume
will be :

,, 30 X 740 22200 ^

y ^ -^ '^ . = =27 6 CC

760 ( I +.003665 X 15) 801.78100

i.e., 30 cc. of a gas at 740 mm. pressure and 15° C. are reduced to 27.6 cc. at
standard pressure and temperature (760 mm. and 0° C).

at : I

.-. V=

:: yi

VI

I +at

: V

l+at

■.-.h:

760

V=-^

YWh

SOLUBILITIES IN WATER AT 15° to 18° C.

Ammonium chloride, . . . ... 36 per 100.

Sodium chloride, . . . . . • 36 ,, ,,

Ammonium sulphate, . . . . . • 5° >> »i

Magnesium sulphate, 125 ,, „

IV.

RECORDING APPARATUS.

There are many forms of recording apparatus in use, and some of them are
described in the text (Lesson XXXIV.). When a number of students have to
be taught to record graphically the results obtained in an experiment, then

384 APPENDIX.

drums moved by some kind of motor are essential. Drums moved by clock-
work, however convenient for individual work, are not suitable for students'
purposes. Hence various devices are used so that many men are enabled to
work at separate drums at the same time.

Motor. — One has first to consider what form of motor one should use to
drive the drums. Some use a small gas-engine, others use a water-motor, as,
for example, the Swiss form of motor made by Schmidt, or the Thirlmere form,
while others prefer an electric motor where electricity is available. Such an
electric motor is made by Siemens and Halske, Berlin, but the initial cost of
this apparatus is considerable.

Transmission of Motion. — Next arises the question as to how the motion is
to be transmitted to the drum. This is done in various ways. In the
Cambridge system, which is adopted foi some of the drums in the Physio-
logical Department of Owens College, the motion is transmitted from the
motor —gas-engine or Thirlmere water-motor placed in the basement — by means
of an endless quick-running cord. This method is extremely convenient, and
the drums are so made that they can be readily arrested, and can also be
made to move at different speeds.

Some use shafting fixed on a sujjport on the wall or ceiling or on a table.
To the shaft are fixed coned pulleys, i.e., wheels of different diameters, whereby
a good range of sj)eeds can be obtained.

Recording Drum. — Next comes the form of drum to be used. In the
Cambridge arrangement the drum can be raised or lowered on a vertical axis
by means of a clutch, while the drum itself can be set in motion or arrested by
means of a handle on the driving pulley. The rate of movement can also be
changed as desired.

Prof Schiifer has also designed a form of drum which is moved by a short
cord passing over coned pulleys fixed to a long rod placed on bearings fixed to
a table and moved by a water-motor. It is made by Backhouse, Physiological
Department, University College, London.

The Oxford pattern is somewhat different from this, and is made by Butler,
Physiological Department, Oxford.

In Bering's large kymograj)hion there is a long sheet of paper (2 metres)
stretched over an ii'on framework, which is moved by clockwork driven by a
weight. In University College, London, to this framework a small cogwheel
is adapted whereby this arrangement can easily be driven by an ordinaiy
motor. It is specially useful for research work where a moderate or slow speed
of the recording surface is required.

In the " i)hysiological recording drum" (fig. 288), as made for Dr
Sherrington, the cylinder is 6 inches by 6 inches, and is so arranged that it
can be used in a vertical or horizontal position, and has a lever by which it
can be instantly started or stopped at any portion of a revolution. The cone
pulley gives a good range of speeds. The brass cylinder is turned perfectly
true in a self acting lathe, and has about 5 inches vertical adjustment. It is
easily removed for the purpose of blacking, and can be run by any light motor
or clockwork, as desired. The whole is mounted upon a substantial cast-iron

APPENDIX.

38:

base, so as to stand firm without clamping down. It is made by C. F. Palmer,

5 Kellett Road, Brixton, S.W.

It costs as above . . . . . . . . . jC^ 12 6

Or with levelling screws (vertical and horizontal) . . .600
Extra for automatic break-key (as shown in position) .086

FlO. 288.— Sherrington's Drum.

Professor de B. Birch's System of Recording Apparatus.— The following
description applies to a system of recording apparatus devised for the Experi-
mental Laboratory in the New Medical School buildings of the Yorkshire
College. The motive power, a small Chicagos top, is geared for reduction of
speed to a 54-inch bicycle wheel, and this again by a cord to a piece of shafting,
19 feet long, running on ball bearings and su])ported by brackets fixed to the
wall of the Laboratory. The shafting carries step cones (I, fig. 289), to these the
drums are geared by cords which run over guide pulleys suspended from the
ceiling in convenient positions. The tension on these cords is kept constant
by counter weights (L), which allow the former the play required in shifting
fiom one speed to another on the cones when changing the rate of revolution

2 B

386

APPENDIX.

APPENDIX. 387

of the drums. An inverted cone outside the pulley (Dj reduces the chance
of the cord being liberated from (D) during the latter operation.

The drums can be run in practically any position on their table, and they
can be removed from the latter without trouble, the gearing cords when not in
use being attached to hooks on the wall close to the shafting. The tables are
thus left completely free for other purposes. The drums are provided with a
starting and stopping contrivance (B) which is independent of the gearing
cord. The driving spindle, which carries the cone (D) and pulley (E), runs
in ball bearings in a rocking carrier which is tilted by the lever (B) either
into contact with or free of (F), a disc attached on the cylinder axle. This
axle is also on ball bearings. The drum can be readily adjusted for height
or removed for covering and smoking without stopping the driving spindle.

The running parts are throughout the system either on centres or on ball
bearings. The resultant diminution of friction is so considerable that the
small motor already mentioned turns eight to twelve cylinders easily with a
25-pound water pressure.

The disc (F) has holes bored into its edge into which a pin or pins can be
fixed for making contact with (H) when automatic stimulation is required at
a definite epoch in the revolution of the cylinder.

The stand (M)^ lends itself to most experiments on frog muscle, nerve, and
heart. The bracket (P), adjustable on the pillar (N), will carry any ordinary
form of muscle chamber, &c. , with slight adaptation. For the support of a
time-marker the "stirrup" (Q) is provided. This turned behind the
muscle-chamber will hold a rod uT)on which the muscle-lever can be rested in
an after-load experiment, or to which a spring can be attached for the muscle
to pull upon in taking an isometric myogram. The same can be accomplished
with the stirrup in the front position by using a second clamp and bent metal
rod.

The points of the writing-levers, after being adjusted by hand, can be finely
adjusted or lifted off the paper by means of the adjusting screw and lever
(0). Stability is conferred by the weight of metal in the stand {Birch).

MICRO-CHE^riCAL DETECTION OF GLYCOGEN, IRON
AND PHOSPHORUS IN VARIOUS CELLS.

Glycogen in Liver Cells. — The essential part of this process is that, as
glycogen is soluble in water, the liver or other tissue supposed to contain the
glycogen must not he placed in water. Feed a rabbit on carrots, and 5-6
hours afterwards kill it ; cut part of the liver into small pieces and harden
them in absolute alcohol. Cut hand sections, moistening the razor with

1 Since tliis stand was devised ahniit three years ago, Dr Birch has become acquainted
with the fact tliat luinne of Basle makes a stand of somewhat similar construction which
he calls the Basler stativ.

388 APPENDIX.

alcohol, or embed and cut in paraffin. Get rid of the paraffin by means of
turpentine, and treat both the paraffin and alcohol sections with chloroform
in which iodine is dissolved, and mount in chloroform balsam containing some
iodine. The brown stain in the liver cells indicates glycogen, which is
deposited chiefly in the cells around the hepatic vein (Dele^i7ie).

Iron, — («.) The tissue — liver ot young animal, or spleen— must be hardened
in alcohol. The sections are transferred to a freshly-prepared solution of
potassium ferrocyanide acidulated with hydrochloric acid. The granules of
iron become blue {Tizzoni).

(b.) Harden the liver in 65 p.c. alcohol, then in 90 p.c. alcohol to which a
few drops of sulphuretted hydrogen are added. After twenty-four hours the
iron granules become green [Zaleski).

Phosphorus. — Place sections of the fresh organ for half an hour in a strong
solution of ammonium molybdate, and then transfer them to a 20 p.c.
solution of pyrogallic acid dissolved in ether. After a few minutes pass
them through spirit and clove oil, and mount in Canada balsam. A com-
pound containing phosphorus is stained yellow or brown, and such compounds
are usually found in the nuclei. It is stated that by this method nucleo-
albumin may be distinguished from mucin [Lilienfeld aiid Monti),

KJELDAHL'S METHOD OF ESTIMATING NITROGEN.

1, Destruction of Organic Matter. — Place in a boiling flask ot 100 cc,
capacity o. i-i gramme of the powdered dry substance. To destroy the organic
matter add 10-20 cc. of the following mixture : 200 cc. pure oil of vitriol, 50
cc, Nordhausen oil of vitriol, phosphoric acid in sticks, 2 grammes, all free
from ammonia. Heat on a wire gauze with a Bunsen-burner, but keep the
temperature below boiling. To hasten the destruction a little potassium
permanganate may be added. Heat for 1-2 hours until the fluid becomes
clear and greenish.

2, Neutralisation. — Cool the flask, add a little water, and wash the contents,
with as little water as possible, into a large flask of 700 cc. capacity.
Neutralise with pure caustic soda or potash (S.G. 1.13). Add a little
metallic zinc to prevent bumj)iiig during the subsequent distillation.

3, Distillation. — Rapidly close the flask with a perforated caoutchouc stopper
through which passes a tube with two i inch bulbs blown upon it. The bulbs are
to collect and prevent the j)assage of soda spray. The tube above the bulbs
passes through a condenser, and the delivery tube end of the condenser tube
passes into a flask containing a measured excess of standard acid (HCl).
Distil the mixture about an hour in the flask, and the ammonia passes over
into the acid.

APPENDIX. 389

4. Titration. ^Determine the amount of acidity in the distillate by titration
with a standard solution of caustic soda or potash, methyl orange being used
as an indicator of the end of the reaction. Methyl orange gives a pink with an
acid, and yellow with an alkali.

The apparatus used in the Physiological Laboratory of Owens College is
that made by Messrs Baird and Tatlock (see their catalogue), and is so
arranged that several estimations can be made simultaneously. Other modi-
fications are in use.

Example. — Suppose o. 15 gramme of the N-substance has been treated with
acid, neutralised, and the ammonia distilled over and received by loo cc. of a
decinormal solution of HCl ( = 10 cc. normal acid). The distillate is then treated
with decinormal caustic soda, and suppose it is found that the neutral point
is reached when 60 cc. of the decinormal soda has been added. The remaining
40 cc. must therefore have been neutralised by the ammonia obtained from the
nitrogenous substance investigated. This 40 cc. of decinormal acid = 4 cc. of
normal acid = 4 cc. ofnormalammonia = 4 x 0.017 = 0.068 gramme of ammonia ;
o. 15 gramme of the substance, therefore, yields 0.068 gramme of ammonia, and
this amount contains 0.056 gramme of nitrogen ; 100 grammes of the substance

investigated will therefore contain ' =37.3 grammes of nitrogen. —

(From Sutton's Volumetric Analysis by Warington.)

MEASURES OF LENGTH.

Metric System.

The standard is the metre ; for multiples of the metre prefixes deca- hecto-
and kilo- are used ; for subdivisions thereof, milli- centi- and deci- are
used just as in the case of the gramme in the table below.

I millimetre =0.001 metre= 0.03937 inch.
I centimetre = 0.01 ,, = 0.3937 ,,
I decimetre =0.10 ,, = 3.93707 inches.
I metre =39-37079 m

English System.

I inch = 25.4 millimetres.

I foot= 12 inches -304.8 „

390

APPENDIX.

MEASURES OF CAPACITY.

Metric System.

A litre is the standard, and is equal to looo cubic centimetres (looo cc);
each cubic centimetre is the volume of i gramme of distilled water at 4° 0.

I cubic centimetre (i cc.) = 16.931 minims.

I litre=icxx3 cc. = i pint 15 oz. 2 drs. 11 min. (35.2154 oz.)

English System.

I minim ■= 0.059

I fluid drachm = 60 minims = 3.549

I fluid ounce = 8 fluid drachms = 28.398 ,,

I pint =20 fluid ounces =567.936 ,,

I gallon = 8 pints = 4.54837 litres,

cubic centimetre,
cubic centimetres.

WEIGHTS.

Metric Stjstem,

I milligramme =

o.ooi gram. =

0.015432 grain.

1 centigramme =

O.OI ,, =

0.154323 „

I decigramme =

0.1 ,, =

1-543235 ,.

I gramme =

I ,, =

15-43235 grains.

I decagramme =

xo grams. =

154-3235

I hectogramme =

100 ,, =

1543-235

I kilogramme =

1000 ,, =)

'5432.35

= :

I lb. 3 oz. 119.8 ,,

[For practical purposes

the kilogramme or

kilo is taken at 2.2 lbs.)

English System.

I grain — 0.0648 gramme.

1 ounce = 437. 5 grains = 28.3595 grammes.
I lb.- 16 oz.- 7000 „ =435-5925 M

APPENDIX. 391

THERMOMETRIC SCALES.

Fahrenheit scale, freezing point of water 32°, boiling point 212°
Reaumur ,, ,, ,, ,, 0° ,, ,, 80'

Centigrade ,, ,, „ ,, 0° ,, ,, 100°

To convert degrees F. into degrees C. subtract 32 and multiply by J or
C = (F - 32)5. To convert C° into F° the formula is F = | C + 32.

SOME OF THE INSTRUTMENT-MAKERS WHO SUPPLY
PHYSIOLOGICAL APPARATUS.

Backhouse, University College, London.
Butler, Physiological Laboratory, Oxford.
Cambridge Scientific Instrument Co.
Hume, Lothian Street, Edinburgh.
Kershaw, Cankerwell Lane, Leeds.
Meyer (J. F. ), Seilergraben 7, Zurich.
Palmer, 5 Kellett Road, Brixton, London.
Petzold, Bayerische Strasse, Leipzig.
Rothe, Wenzelbad, Prague.
Siedentopf, Wiirzburg.
Runne, Basel and Heidelberg.
Verdin, Rue Linne 7, Paris.
Zimmermann, Leipzig.

INDEX.

Aberration— Chromatic, 330.
,, spherical, 330.

Absorption-bands, 47.
Accommodation, 331.

„ line of, 335.

Aceto-acetic acid, 146.
Aceton, 146.

Achroo-dextrin, 18, 22, 69.
Acid-albumin, 8, 73.
Acid-hfematin, 50.
Acidulated brine, 138.
Acme sacchar-ureameter, 145.
Action-current of muscle, 237.

,, nerve, 238.

Acuity of vision, 339.
Adamkiewicz, reaction of, 3.
^sthesiometer, 367.
After-images, 3.")9.
After-load, 200.
Air expired, 311.

,, analysis of, 313.

Albumenoids, 13.
Albumin, 1.

,, coagulation temperature

of, 4.

,, derived, 7.

egg, 14.

,, general reactions, 2.

,, native, 4.

,, nitrogen in, 3.

,, serum, 5.

,, soluble, 4.

,, sulphur in, 3.

,, vegetable, 98.

Albumin — Estimation of, 139.

,, in urine, 136.

,, tests for, 137.

Albuminates, 73.
Albuminimeter, 139.
Albuminuria, 136.
Albumoses, 8, 73, 78.
Albumosuria, 139.

Alkali-albumin, 7.
Alkali-hsematin, 51.
,, reduced, 51.
Alkaline phosphates, 112.
Amalgamation of zinc, 158.

,, mixture, 158.

Amidulin, 22.
Ammonium carbonate, 109, 382.

„ urate, 151.

Ampere, 160.
Amyl nitrite, 294.
Amyloid substance, 11,
Amylopsin, 80.
Amyloses, 16.
Anaglyph, 363.
Analysis of a fluid, 32.
solid, 156.
Animal starch, 19.
Anode, 157.
Apex-preparation, 282.
Apncea, 310.

Apparent movements, 350.
Aromatic compounds, 378.
Arterial pressure, 301,
Artificial eye, 350, 365.
,, gastric juice, 71.
,, pancreatic juice, 79.
Aristotle's experiment, 368.
Astigmatism, 335.
Atroftin on heai't, 277.
Auto laryngoscopy, 316.
Automatic break excitation, 201.
Auxocardia, 291.

Barfoed's solution, 2.
Baryta mixture, 124.
Bayiiss' writing-point, 270.
Benham's top, 362.
Benzoic acid, 131.
Benzo-purpurin, 76.
Bergmann's experiment, 340.
Bernard's method for curare, 193.

INDEX.

393

Bernstein's method for heart, 261.
Bezold's experiment, 330.
Bichromate cell, 159.
Biederniann's modification, 243.
Bile, 87.

acids, 87.
actions of, 89.
cholesterin in, 89.
crystallised, 87.
Gmelin's test, 88, 141.
in urine, 141.

Pettenkofer's test, 88, 141.
pif^ments, 88.
salts, 87.
Bile-acids in urine, 111.
Bile-pigments in urine, 141.
Bilin, 87.
Bilirubin, 88.
Biliverdin, 88.
Binocular contrast, 359.

,, vision, 345.
Biuret reaction, 9, 119.
Bismuth test, 21,
Black-band experiments, 342.
Black's experiment, 311.
Blind spot, 337.
Blix's myograph, 217.
Blood, 33.

,, acids on, 55.
,, action of saline solution, 34.
,, Buchanan's experiments, 39.
,, clot, 35.
,, coagulation of, 35.
,, corpuscles, 43.
,, defibrinated, 37.
,, grape-sngar in, 42.
,, laky, 33.
,, mammalian, 35.
,, nitrites on, 53.
,, plasma, 35.
,, reaction, 33.
,, red cor[)Uscles of, 34.
,, serum of, 35, 37-
,, sodium fluoride on, 54.
,, specific gravity of, 34.
,, spectroscopy of, 46.
,, stains, 59.
,, transparent, 33.
Blood in urine, 140.
Blood-corpuscles, 43.

,, numeration of, 43.

Blood-gases, 312.
Blood-i>ressure, 300, 306.

„ tracings, 304.

Bone, 81.
Bottger's test, 21, 142.

Bowditch's rotating coil, 167.

Bread, 99.

Break extra -current, 173.

Break-shock, 171.

Brine-test, 138.

British gum, 18.

Briicke's method for glycogen, 91.

Brush electrodes, 237.

Bu'>hapan's experiments, 39.

VJutiy coat, 35.

Burette, 116.

Calcium phosj)hate, 112.
Calcuii, urinary, 149.
Cane-sugar, 24.

,, estimation of, 25.

,, inversion of, 24.

Cannula, 305.

Capillaries, pressure in, 300.
Capillary electrometer, 233.
Carbohydrates, 15, 376.

,, classification of, 16.

,, general characters, 1.^.

,, rotatory power, 28.

Carbolo-chloride of iron test, 77.
Carbonic-oxide haemoglobin, 47.

,, spectrum of, 57.

Cardiac delay, 272.
Cardiograph, 287.
Casein, 11.
Caseiuogcn, 8, 95.
Cathode, 157.

,, as stimulus, 249.
Cellulose, 19.

Centrifugal machine, 43, 147.
Charpentier's experiments, 342.
Chemical stimulation, 182.
Chloral, 321.
Cholesterin, 89, 90.
Cholicacid, 88.
Chondrin, 14.
Clion<lrigen, 14.
Cliordogram, 206.
Choroidal illumination, 359.
Christison's formula, lOtJ.
Cliromatic aberration, 330.
Chromo-cytometer, 62.
Chronograph, 211.
Ciliary motion, 177.
Circulation, scheme of, 297.

,, microscopic examination

of, 300.
Circumpolarisatiou, 25.
Clerk-Maxwell's experiment, 340.
Coagulated proteids, 10.
Coagulation of blood 35.

394

INDEX.

Coagulation, action of neutral salts,36.
„ ,, of cold, 35, 40.

,, experiments, 39.

,, oxalates, 36.

Cold— Effects on blood, 35.
,, ,, heart, 264.

,, „ muscle, 213.

,, ,, nerve, 257.

Cold spots, 369.
Collagen, 13.
Colloid, 19.

Colorinietric method, 65.
Colour-blindness, 353.

,, sensations, 352. «

Coloured fringes, 330.

,, shadows, 358.
Combined sulphuric acid, 112.
Commutator, 165.
Conduction in nerve, 247, 25f).
Congo-red, 76.
Constant current, 16(1.

,, ,, action of, 254.

,, ,, ,, on heart, 278.

Contact key, 162.

„ sense of, 370.
Contraction — maximal, 199.
,, minimal, 198.

,, paradoxical, 241.

,, secondary, 241.

,, without metals, 239.

Contrast, 354.

„ binocular, 359.
Grank-myogmph, 200.
Crystal lin, 7.
Ciirare, 190, 193.
Curdling of milk, 96.
Current, demarcation, 234, 237.
„ of heart, 242.
,, of injury, 234.
Cystin, 151.

Daniell's cell, 157.
Darby's Huid meat, 9.
D'Arsonval's N. P. electrodes, 237.
Defibrinaied blood, 37.
Deglutition apnoea, 310.
Demarcation cuirents, 234.
Deposits in urine — organised, 147.

,, unorganised, 147.

Depressor nerve, 302.
Derived albumins, 7.
Di'spretz's signal, 210.
Detector, 159.
Deutero-albumose, 78.
Dextrin, 18.

,, preparation of, 19.

Dextrin, varieties of, 22.
Dextrose, 20.

, , reducing power of, 70.

,, rotatory power of, 26.
Diabetes, 143.
Dialyser, 78.
Diffusion, 329.
Digestion — Biliary, 87.

,, gastric, 71.

,, pancreatic, 79.

,, salivary, 67.

Diplopia monoph thai mica, 336.
Direct stimulation, 188.

,, vision, 339.
Direction, judgment of, 348.
Disacchariiles, 16.
Distance, judgment of, 348.
Donne's test, 148,
Double conduction in nerve, 253.
Du Bois electrodes, 169.
,, induction coil, 166.

key, 160.
,, rheochord, 249.
Dudgeon's sphygmograph, 294.
Dupre's apparatus, 121.
Duration of impressions, 342.
Dynamometers, 189.

Ear, 371.

Earthy phosphates, 112.
Egg-albumin, 4.
Elasticity of artery, 218.
,, lungs 309.

,, muscle, 216.

Elastin, 14.

Electrical keys — Brodie's, 175.
,, Contact, 162.

„ Du Bois, 160.

„ mercury, 162.

„ Morse, 162.

plug, 163.
„ spring, 162.

trigger. 162.
Electrical constant cuirent, 184.
„ repeated shocks, 184.
,, single shocks, 183.
,, stimulation, 183.
,, stimuli, 181.
Electrodes, 168.

,, d'Arsonval's, 237.

„ brush, 237.

„ Du Bois, 169.

,, for nerve, 304.

,, non-polarisable, 233.

,, polarisation of, 169.

Electrometer, capillary, 238.

INDEX.

395

Electro-motive phenomena of muscle,
235.

Electro-motive phenomena of heart,
238, 242.

Electro-motive phenomena of electro-
tonic variation, 248.

Electro-tonic variation of excitability,
243.

,, ,, electro-motivity,

248.

Eiectrotonus, 243.

iillis' air piston recorder, 295

Enmlsion, 30, 83.

l']nd()cardial pressure, 281.

Eiigelinann's experiment, 254.

Entoptical vision, 341.

Enzymes, 68, 75.

Erdniann's float, 116.

Ergngiaph, 230.

Erythro-ilextriii, 18, 22, 69.

Esliach's aibuininimeter, 139.

Ewald's coil, 167.

Examination of a fluiil for proteids
au't carbohydrates, 32, 154.

Examination of a solid, 156.

Excitability, muscular, 190.

„ V. conductivity, 256.

,, of nerve, 254, 256.

Exhaustion in nerve and muscle, 225.

Exporimentum mirabile, 327.

Expired air, 311.

Extensibility of muscle, 216.

Extensors, excitability of, 256.

Extra-current, 173.

Far point, 333.
Faradic electiicity, 160.
Faradisation, 172,
Fatigue of muscle, 223.

„ nerve, 225.

Fats, neutral, 29.
Fehliiig's solution, 142.
Ferments — Amylopsin, 80.

,, fibrin, 40.

,, milk curdling, 84, 96.

,, pancreatic, 80.

,, pepsin, 72.

,, pialyn, 84.

,, ptyalin, 68.

,, rennet, 7.'>.

,, steapsiii, 84.

,, trypsin, 81.

,, in urine, 135,

Fibrin, 10, 37.
Fibrin-ferment, 40.
Fibrinogen, 7, 36, 39.

Field of vision, 344.
Flexors, excitability of, 256.
Flour, 98.
Fovea centralis, 339.

,, shadows on, 341.

Fractional heat-coagulation, 11.
Furfurol, 88.

Gad's emulsion experiment, 30.
Gall stones, 89.
Galvanic electricity, 157.
Galvani's experiment, 239.
Galvanometer, 251.
Galvanoscope, 159.
Garrod's test, 129.
Gas-.sphyj;moscope, 295.
Gases in blood, 312.
Gaskell's clamp, 267.

,, heart lever, 266,
Gastric action on milk, 75.

,, content'^, examination of, 79.

,, digestion, 72.

,, juice, 72.

,, peptones, 74.

, , products of, 73.
Gelatin, 13.

Gerrard's urea apparatus, 126.
Globin, 7.
Globulins, 6.
Globulinuria, 138.
Glucose, 20.

,, in blood, 42.

,, to prepare, 22.

,, rotatory power of, 26.
Glucoses, 16.
Gluten, 11, 98.
Glycerin; 29.
Glycin, 104.
Glyco-cholic acid, 87.
Glycocol, 104.
Glycogen, 19, 91.

., preparation of, 91.
,, tests for, 93, 387.
Glycosamin, 103.
Glycosuria, 141.
Gmelin's test, 88.
Goltz's tapping experiment, 287.
Gotch's arrangement for excised

heart, 269.
Gotch's localised cold nerve, 258,
Gracilis, experiment on, 2.^3.
Grape-sugar, 20, 42.
Graphic method, 194.
Grove's cell, 158,
Griirihagen's experiment, 256.
Guaiacum test, 140.

396

INDEX.

Guanin, 104.

Gymnema sylvestre, 371.

Haematin, 52.

,, preparation of, 58.

Haeniatinonieter, 49.
Hajmatoporphyrin, 53.
Hsematoscope, 49.
Hsematuria, 140.
Haeniin, 59.
Hfeiiiochromogen, 51.
Hsemocytometer, 43.
Hemoglobin, 34.

,, ash of, 43.

,, carbonic oxide, 49, 57.

,, crystals of, 45.

,, estimation of, 59.

,, nitrites on, 53.

,, non-ditfusibility, 34.

oxy-, 47.
,, ozone test, 46.

' ,, preparation of, 45, 65.

,, reduced, 48, 56.

,, spectrum of, 47, 55.

Haemoglobinometer, 59.
Hsenioglobinuria, 140.
Haemometer, 60.
Hand-electrodes, 168.
Haploscope, 360,
Haser-Trapp's coefficient, 106
Haycraft's method for S. G. of blood,
34
,, uric acid, 136.

Hearing, 371.

Heart — Action of drugs on, 277.
apex, 282.
atropin on, 277.
casts of, 285,
clamp, 267.
cold on, 261.
cotistant current on, 278.
current of frog, 242.
endocardial pressure, 281.
excised, 260, 269.
frog's, 259.

graphic record of, 262.
heat on, 261.
inhibition of, 271.
inhibitory centre, 271.
latent jieriod, 272.
lever, 263.
mammal's, 286.
motor centres, 272.
movements of, 262.
muscarine, 277.
nervous system ou, 279.

Heart —effect of temperature on, 260.
264, 267.

,, nicotin ou, 277.

,, ox, 286.

,, perfusion, 279.

,, pllocarpin on, 277.

,, record of, 262.

,, reflex inhibition, 271, 287.

,, section of, 261.

,, sounds of, 286.

,, staircase of, 271, 278.

,, Stannius's experiment, 270.

,, suspension methods, 266.

,, swallowing on, 287.

,, sympathetic on, 275.

,, tonometer, 282.

,, tortoise's, 265.

,, vagus on, 273, 305.

,, valves of, 284.
Heat — Effect on cilia, 177.

,, ,, heart, 264.

,. ,, muscle, 214.

,, ,, nerve, 255.

Heat-rigor of muscle, 206.
Heller's test, 137.

blood test, 140.
Helmholtz's modification, 174,
Hernial bumose, 8, 78.
Hempel's method, 314.
Hering's apparatus for contrast, 357.
Hetero-albumose, 78.
Hey wood's experiment, 313.
Hippuric acid^ 131.
Holmgren's worsteds, 354.
Hot spots, 369.

Hufner's urea apparatus, 120, 125.
Hydrocele fluid, 39.
Hydrostatic test, 310,
Hypobiomite method, 120.
Hypobromite of sodium, 121.

Hluminated ox heart, 286.
Illusions connected with skin, 370.
Image, formation of, 329.
Impressions, duration of, 342.
Independent muscular excitability,

190.
Indican, 134.
Indiff'erent fluid, 179.
Indigo-forming substance, 134.
Indirect stimulation, 188.

„ vision, 339.
Indol, 83, 85.
Induced electricity, 166.
Induction coil, 163.

,, Ewald's form, 167.

INDEX.

397

Induction, new form of, 166.

,, graduated form of, 167.

,, .shocks, effects of, 171.
Iiifl iiuination, 300.
Inhibition of ralibit's heart, 287.
Inhibitory heart arre-st, 271, 287.
liiterrupt<2d current, 172.
Intra-omilar jiressure, 367.
Intra-iiK-ural pressure, 3 '2.
Intra-thoracic pres.sure, 311.
Inverted image, 329.
Invert-sugar, 25.
Iodine solution, 18.
Iris, movements, 326.
Iron, test for. 388.
Irradiation, 346.
Isometric contraction, 203.
Isotonic ,, 203.

Jaffe's test, 133.
Judgment of direction, 348.

,, ofdiistance, 348.

,, of size, 318.

Keratin, 14.

Key — Hrodie's, 175.
,, Du B'lis-Revmond's, 160.
,, mercury, 162.
,, Morse, 162.
„ plug, 163.
,, spring or contact, 162.
„ trigger, 163.
Kjeldahl's method, 127, 388.
Knee-jerk, 321.
Koenig's Hames, 317.
Kreatin, 101.
Kreatinin, 132.

Kiihne's — Curare experiment, 132,
194.
,, nerve current experiment,

242.
,, eye, 3E0.

,, gastric juice, 71.

,, gracilis experiment, 2.i3.

,, Tnuscle-press, 242.

,, pancreas powder, 80.

,, .xartorius ex|)eriment, 191.

Kiilz's metliod for glycogen, 91.
Kymograph, 301.

Lact-albumin, 6, 95.
Lactic aciil, 77.
Lactoscope, 98.
Lactose, 23, 95.
I^nmhert's method, 3.52.
Lardacein, 11.

Laryngoscope, 315.
Latent period ol heart, 272.
,, reHex, 319.

,, vagus, 275.

Laurent's polarimeter, 26.
Lecithin, 10:5.
I.,egars test, 146.
Leucin, 82, 85.
Lieben'.s test, 146.
Lieberkiihn's jelly, 7.
Liebermann's n-action, 3.
Liebig's extra';t of meat, 101.
Ligature, effect of, 285.
Liquor pancreaticus, 80.

,, pepticus, 72
Listing's reduced eye, 337.
Litliates, 130.
Livei-, extracts of, 93.
Load on muscle, 214.
Localit}', sense of, 367.
Ludwig's kymograh, 301.

,, sphygmograph, 294.
Lungs, elasticity of, 309.
Lustre, 361.
Lymph-hearts, 300.
Lysatinin, 3 SO.
Lysin, 380.

Magnesia mixture, 113.
Magnetic tuning-fork, 222.
Make shocks, 171.
Malt extract, 70.
Maltose, 22, 69.

,, estimation of, 23.

,, reducing power, 23.

,, .saliv.iry digestion, 69.
Manometric flames, 317.
Marey's niyogiapli, 213.

,, sphvgniograph, 291.

,, tambour, 228.
Marriotte's experiment, 337
Maximal contraction, 198.
Maxwell's experiment, 340.
.Measures of capacitv, 390.
,, length," 389.
i .Meat, extract of, 101.
.Mechanical stimulation, ISl.
Meiocardia, 291.
Mercurial key, 162.
Metaphosphoric acid, 138.
Methiemoglobin, 52, 54.
Methyl violet, 76.
Meyer on contrast, 356.
Metronome, 22-'.
Micro-spectroscopes, 17.

398

INDEX.

Milk, 94.

,, caseinogen of, 95.

,, coagulation of, 97.

,, curaling, of, 96.

,, fat of, 9d.

,, gastric juice on, 75.

,, lactalbumin of, 95.

., opacity of, 98.

,, pancreatic juice oil, 84.

,, to peptonise, 75, S5.

,, rennet on, 75.

,, salts of, 97.

,, souring of, 96.

,, sugar of, 95,
Milk-curdling ferment, 96.
Milk-sugar, 23, 95.
Millon's reagent, 2.
Mineral v. organic acids, 76.
Minimal contraction, 199.
Molir's test, 77.
Moist chamber, 197.
Molisch's test, 22.
Mono.'-accharides, 16.
Moore's test, 20.
Morse key, 162.
Mosso's ergograph, 2-30.
Mucin, 14.
Mucus in urine, 135.
Mulberry calculus, 152.
Miiller's valves, 312.

,, experiment, 295.
Murexide te.st, 128.
Musc?e volitantes, 341.
Muscarin on heart, 277-
Muscle — Action current of, 237.

,, action of heat, 214.

,, ,, veiatria, 214.

,, curve of, 203.

,, demarcation current, 234.

,, direct stimulation of, 188.
effect of load, 214.

,, ,, two .shocks, 219.

,, elasticity, 216.

,, electrical stimulation, 181.

,, exi'italdlity, 192.

,, extensibility of, 226.

,, extra tives of, lul.

,, extracts of, 100.

,, fatigue, 223.

„ independent excitability of,
190.

,, indirect stimulation of, 188.

,, lever, 197.

„ load, 214.

,, on mercury, 185.

,, pigments of, 102.

Muscle — plasma of, 102.
,, pre.ss, 242.
,, proteids, 102.
,, reaction of, 99.
,, rupturing strain, 189.
,, serum, 102.
,, single contraction, 184, 197.
,, sound, 189.
,, stimulation of, 183.
,, successive shocks on, 2 1 9.
,, temperature on, 213.
,, tension of, 204.
,, tetanus, 220.
,, thickening of, 22S.
,, twitch, 198.
,, veratria on, 214.
,, wave, 226.
,, work of, 205.
Muscular contraction, 213.
,, load on, 214.
,, sense, 370.
,, temjierature on, 213.
,, veratria on, 214.
Myelin-fornis, 104.

Myographic experiments on man, 229.
Myographs, 196.

Blix's, 217.
,, crank, 200.

,, Fredericq's, 213.

,, Marey's, 213.

,, pendulum, 206.

,, spring, 208.

Myo.sin, 7, 11, lo2.
Myosiudgen, 100.

Native albumins, 4.
Neefs hammer, 172.
Negative variation, 236.

,, after-images, 360.
Nerve-muscle preparation, 177, 179.
Nerves — action current, 238.

,, cold on, 257.

,, demarcation current, 237.

,, double conduction, 253.

,, excitability of, 192.

,, fatigue of, 225.

,, localised cold on, 258.

,, salt on, 255.

,, section of, 256.

., unequal excitability, 254.

,, velocity of energy, 250.
Neuramoebimeter, 326.
Neuro-keratin, 14.
Nicotin on heart, 277.
Nitrites, 53.

,, in saliva, 68.
Nitrogen, estimation of, 388.

INDEX.

399

Non-polarisable electrodes, 233, 237.
Normal saline. 179.

,, soda solution, 110.

,, urobilin, 133.
Nuclein, 103.
Nucleo-albumin, 104.

Ohm, 160.

Oils, chemistry of, 29.

Olein, 29.

Ophthalmoscope, 364.

Ophthalmotouoineter, 367.

Organic acids as tests, 76.

Organised deposits in urine, 147.

Ossein, 30.

Ox-heart, 286.

Oxalate plasma, 36.

Oxalate of lime, 152.

Oxy haemoglobin, 47.

, , crystals of, 45.

,, reduction of, 49.

,, spectrum of, 47, 49.

Palmitin, 29.

Pancreatic action on fats, 83.

,, ,, on proteids, 81.

,, ,, on starch, 80.

,, digestion, 79.

,, extracts, 80.

„ juice, 79.

„ milk, 84.

,, peptones, 81.

Paradoxical contraction, 241.
Paraglobulin, 38
Pavy's solution, 144.
Pea-meal, 99.
Pendulum myograph, 206.
Pepsin, 72, 78.
Peptones, 9. 74, 78,

,, diti'usibility of, 10.

,, tests for, 9.

,, Witte's, 8.
Peptonised milk, 75.
Peptonuria, 139.
Perfusion, 279, 306.
Perimetry, 344.
Periplieral projection, 369.
Perrin's eye, 365.
Pettenkofer's test, 88.
Pfliiger's law of contraction, 247.
Phakoscope, 333.
Phenol in urine, 134.
,, tests for, 146.
Phenyl-glucosazon, 21.
,, tests for, 146.
,, hydrazin test, 15, 21.
„ maltosazon, 2^,

Phloro-glucin vanillin, 76.
Phosphenes, 340.
Phosphoric acid, ll.">.

, , volumetric process for, 115.

Phosphorus, test for, 388.
Physiological apparatus, list of makers
of, 391.
,, rheoscope, 240.

Picric acid, 138.
Picro-carmine, sjjectrum of, 54.
Picro-saecliarin)eter, 144.
Pigments of bile, 88.

,, urine, 134.

Pilocarpin on heart, 277.
Pince niyograj)hique, 228.
Piotrowski's reaction, 2.
Piston -recorder, 281.
Pithing, 176.
Plasma of blood, 36.
,, of muscle, 102.
,, salted, 36.
Plasniine, 36.

,, of muscle, 102
Plattner's bile, 87.
Pletli3'smograph, 295.
Plug key, 163.

Pohl's commutator, 165, 193.
Poisons on heart, 277.
,, on muscle, 214.
,, on spinal cord, 320.
Polarimeters, 25.
Polarisation of electrode-s, 169.
Polaristrobometer, 28.
Polygraj.h, 289.
Polv.sacchnrides, 16.
Po.sitive after-images, 359.
Potassio-mercuric iodide, 93.
Potassium bronnde, 321.
chloride, 321.

,, sulphocyanide, 68.

Preformed sulphuric acid, 112.
Pressure sense, 369.
Proteids, 1.

,, classification of, 4.

,, coagulated, I'l.

,, general reactions, 2.

,, non-dilfusiliiliiy, 3.

,, removal ot, 12.

,, rotatory power, 28.
Proteoses, 8, 73.
Proto-albumo.se, 78.
Ptyalin, 68.
Pulse, 291.
Pulse -wave, 296.
PupU, 367.

,, albino, 836.

400

INDEX.

Pupil reflex, 336.
Purkinje's figures, 341.

,, Sanson's images, 280.
Pus in urine, 147.
Putrefactive products of pancreatic

digestion, 83.
Pyroeatcchin, 147.
P3'uria, 147.

Quantitative estimation of acidity,
110.

,, ,, chlorides,

111.

,, „ phosphates,

115.

» sugar,

143.

,, ,, urea, 120.

,, ,, uric acid,

135.

Radial movement, 350.

Ra^ona Scina, 356.

Ranvier's emulsion experiment, 30.

Reaction, biuret, 9.

,, of Adauikiewicz, 3.

,, of Liebermann, 3.

,, of Piotrowski, 2.

,, of Utfelmann, 77.

,, xanthoproteic, 2.
Reaction-time, 323.
Recording apjiaratus, 194, 3S3.
Reduced aikali-hfematin, 52.

,, hwuioglobin, 48.

,, ,, spectrum of, 49.

Ri'flex action, 318.
Rennet, 75.
Repeated shocks, 172.
Ri'spiration, voluntary, 310.

,, on pulse, 295.
Respiratory movements, 308.

,, of Irog, 311.
Retinal shadows, 341.
Reverser, 166.
Rlieochords, 163, 245, 249.
Riieometer, 298.
Hlieoiiome, 187.
Rlieoscopic fro^', 240.
liigor mortis, 100.
Ringer's fluid, 280.
Ritter's tetanus, 249.
Rosentlial's modification, 193.
Roy's tonometer, 282.

Saccharimeter, 143.

Saccharoses, 16.

Saliva, 67.

,, digestive action of, 68.

,, oxidising power of, 71.
Salivary digestion, 68.
,, effects on, 69.
Saponification, 30.
Saitorius of frog, 186.
Scheiner's experiment, 331.
Sehitf's test, 129.
Secondary contraction, 240, 241.

,, Biedermann's modification
243.

,, tetanus, 241.
Semi-membranosus and gracilis pre-

]iaration, 179.
Serum of blood, 35, 37.

,, proteids of, 38.

,, to obtain, 41.
Serum, salts of, 40.

,, sugar of, 40.
Serum-albumin, 5, 38, 41, 136

„ globulin, 6, 38, 41, 138.

,, -proteids, 38.

,, coagulation of, 39.
Shadows, coloured, 358.
,, on retina, 341.

Shielded electrodes, 168,
Shunt, 234.

Simple muscle curve, 202.
Sinuiltaneous contrast, 354.
Single contraction, 185.
Single induction sliocks, 171.
Size, 348.
Skatol, 83.
Smell, 370.
Soap, 30.

Soluble albumin, 4.
Soluble starch, 69,
Soluhilities, table of, 383.
Specific rotation, 25.
Spectroscope, 46.
Spherical aberration, 330.
Sphygmographs, 291.
Sj)hygniomanometer, 306.
Sphygmoscope, 295.
Spinal nerve roots, 322.
Spirometer, 311.
Spring key, 162.
S{)ring myograph, 208, 213.
Staircase, 271, 278.
Stannius's experiment, 270.
Starch, 17.

,, action of malt, 70.

,, animal, 19.

,, colloid, 18, 70.

,, conversion to sugar, 22.

INDEX.

401

Starch, potato-, 18.

,, soluble, 22.

,, stages to glucose, 22, 25.

,, stages to maltose, 69.

,, under microscope, 17.

,, under polariscope, 18.
Stearin, 29.

Steele's apparatus, for urea, 123.
Stellar phosphate, 114.
Stereoscope, 361.
Stethographs, 308.
Stethometer, 310.
Stethoscope, 286.
Stimuli, 181.
Stokes's fluid, 49.
Strasburger's test, 88.
Strobic discs, 350.
Struggle of fields of vision, 361.
Strychnia, 320.

Successive liglit induction, 358.
Successive shocks, 219.
Sugar in urine, estimation of, lAl

143, 145.
Sugar fermentation method, 137.

,, tests for, 142.
Sulphocj-anides, 68.
Sulphur test for bile, 88.
Suprarenal extract, 307.
Swallowing on heart, 287, 312.
Sympathetic of frog, 275.

,, rabbit, 302.

Syntonin, 8.

Talbot's law, 342.
Tambour, 228.
Tapping experiment, 287.
Taste, 370.
Taurin, 90.
Taurocholic acid, 87.
Telephone experiment, 189.
Temperature, sense of, 368.

,, on muscle, 213.

Tendon, to rupture, 189.
Tension of muscle, 204.

„ recorder, 205.
Test meal, 79.
Test types, 282.
Tetauomotor, 182,
Tetanus, 220, 221.

,, secondary, 241.
Tetra paper, 71.
Thermal stimulation, 182.
Thermometric scales, 391.
Time-markers, 210.
Tissue-fibrinogen, 104.
Tonometer, 282.

Total N., estimation of, 127.

Touch, 367.

Trichloracetic acid, 138.

Trigger key, 162.

Triple phosphate, 114.

Trommer's test, 20, 142.

Tropaeolin, 76.

Trypsin, 81.

Tryptic digestion, 81.

Tubes, rigid and elastic, 295, 298.

Turck's method, 319.

Twitch, 185, 198.

Tyro.sin, 82, 86.

Uffelmann's reaction, 77.
Unipolar stimulation, 186.
Unorganised deposits in urine, 149.
Urates, 130.
Urea, 117.
,, nitrate, 117.
,, oxalate, 118.
,, preparation, 117.
,, quantity, 119.
,, reactions of, 119.
,, synthesis of, \-^6.
,, volumetric analysis, 120, 123.
Ureameter, 123, 126.

,, ot Doremus, 123.
Uric acid, 127.
,, estimation of, 135.
,, reactions, 128.
,, salts of, 130.
,, quantity, 127.
,, tests, 128.
Urinary calculi, 149.

,, deposits, 147, 149.
Urine, 104.

,, abnormal constituents, 13d.

,, acidity, 107, 110.

„ albumin in, 136.

,, alkalinity, 107.

„ bile in, 141.

,, blood in, 140.

,, chlorides, 111.

,, colour, 105.

„ colouring-matters, 183.

„ diabetic, 142.

„ deposits in, 147, 149.

„ fermentations of, 108.

,, ferments in, 135.

,, general examination of, 168.

„ inorganic bodies, 110.

,, mucus in, 135.

„ odour, 106.

„ organic bodies, 117.

„ phenol in, 134.

20

402

INDEX.

Urine, phosphates in, 112.

,, pigments of, 134.

,, pus in, 147.

,, quantity, 105.

,, reaction, 107.

,, reaction to reagents, 135.

„ solids in, 106.

,, specific gravity, 105.

,, sugar in, 142.

,, sulphates in, 111.

,, transparency, 108.

,, urates in, 130.

,, urea in, 117.

,, uric acid in, 127.
Urinometer, 105.
Urobilin, 133.

„ febrile, 134.

Vagus of frog, 273.

,, ,, latent period of, 275.

„ rabbit, 302.

,, on heart, 305.
Valsalva's experiment, 295.
Valves of heart. 284,
Vanillin, 76.
Varni.sh, 197.
Vascular tonus, 279.
Veratria, 214.
Vibrating reed, 211.
Vision, physiology of, 329.
Visual axes, 349.

,, judgments, 347.
Vital capacity, 311,
Vitellin, 7.

Vogel's lactoscope, 98.
Volkmann's experiment, 338.

Volt, 160.

Volumetric process, 114.

„ for phosphoric

acid, 115.
,, for sugar, 143.

for urea, 120, 123
Vomit, examination of, 79.
Vowel-sounds, 317.

Wave-lengths, 55,

Wave of muscle, 228.

Weber's circles, 370.

Weights, 390.

Weyl's test, 133.

Wlieaten flour, 98.

Wheatstone's flutteiing hearts, 330.

Wheel movements, 345.

Whistle, Galton's, 372.

White of egg, 1, 2.

Wild's apiiaratus, 228.

,, polaristrobometer, 28.
Wilke's reagent paper, 158.
Witte's peptones, 8.
Wittich's method, 71.
Work done by muscle, 205.
Writing point of Bayliss, 270.

Xanthin, 101.

,, bodies, 381,
Xanthoproteic reaction, 2.

Yellow spot, 340.

Zbllner's lines, 347.
Zymogen, 80.

fHB £NJX