COLUMBIA LIBRARIES OFFSITE HEALTH SCIENCES STANDARD nm HX64171930 QP44.St5 1890 Outlines of practica HI >■;•■••.■■;:: . IFFIN'S SCIENTIFIC TEXT-BOOKS RECAP OK 4 COLUMBIA UNIVERSITY DEPARTMENT OF PHYSIOLOGY THE JOHN G. CURTIS LIBRARY 1 J imim »".vi. m A I iTV B ■ ■ I ■■■ 41 • • -a* ■ m ■ ' ■ Edit* '-V- ■ ■*- ■■■•v*:fc ■ I T ■ r ■ ■ s# ■ w Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/outlinesofpracti1890stir OUTLINES OF PKACTICAL PHYSIOLOGY. STUDENTS' TEXT-BOOKS. Companion- Volume by the same Author. In extra crown 8vo, with 344 Illustrations, cloth, 12s. 6d. PRACTICAL HISTOLOGY (Outlines of) : A Manual for Students. "The general plan of the work is admirable. ... It is very evident that the suggestions given are the outcome of a prolonged experience in teaching Practical Histology, combined with a REMARKABLE JUDGMENT in the selection of METHODS." — British Medical Journal. By Professors LANDOIS and STIRLING. Third Edition. Medium 8vo, with 692 Woodcuts. 34s. HUMAN PHYSIOLOGY (A Text-Book of) : Including Histology and Microscopical Anatomy, with Special Reference to Practical Medicine. By Dr. L. Landois, of Greifswald. Translated from the Fifth German Edition, with Annotations and Additions, by Wm, Stirling, M.D., Sc.D. "The MOST complete resume of all the facts in Physiology in the language."— Lancet. By Professor A. MACALISTER, F.R.S. In medium 8vo, with 816 Illustrations, cloth, 36s. HUMAN ANATOMY, Systematic and Topographical (A Text- Book of) : Including the Embryology, Histology, and Morphology of Man, with Special Reference to the Requirements of Practical Surgery and Medi- cine. By A. Macalister, M.D., F.R.S., Professor of Anatomy, University of Cambridge. " By far the most important work on this subject which has appeared in recent years. " — Lancet. By Professor A. C. HADDON, M.A. In medium 8vo, with 192 Illustrations, cloth, 18s. EMBRYOLOGY (An Introduction to the Study of). For the Use of Students. By A. C. Haddon, M.A., Professor of Zoology, Royal College of Science, Dublin. " An excellent resume of recent research." — Lancet. By W. ELBORNE, F.C.S., F.L.S. In extra crown 8vo, with Lithographic Plates, and numerous Illustrations, cloth, 8s. 6d. PHARMACY AND MATERIA MEDICA (A Laboratory Course) : Including the Principles and Practice of Dispensing. By W. Elborne, F.L.S. , late Assistant-Lecturer on Materia Medica and Pharmacy in Owens College, Manchester. "Mr. Elborne evidently appreciates the requirements of medical students, and there can be no doubt but that one who works through this course will obtain an excellent insight into Chemical Pharmacy." — British Medical Journal. By J. R. AINSWORTH DAVIS, B.A. In extra crown 8vo, with 158 Illustrations, cloth, 12s. 6d. BIOLOGY (A Text-Book of). Comprising Vegetable and Animal Morphology and Physiology. By J. R. Ainsworth Davis, B.A., Lecturer on Biology at the University College of Wales, Aberystwyth. " The volume is literally packed with information. " — Glasgoxo Medical Journal, LONDON: CHARLES GRIFFIN AND COMPANY. OUTLINES OP PRACTICAL PHYSIOLOGY: BEING A /IDanual for tbe ipb^siolooical Xaboratorp, INCLUDING CHEMICAL AND EXPERIMENTAL PHYSIOLOGY, WITH REFERENCE TO PRACTICAL MEDICINE. BY WILLIAM STIRLING, M.D., Sc.D., BRACKENBURY PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN THE OWENS COLLEGE. AND YICTORIA UNIVERSITY, MANCHESTER ; AND EXAMINER IN PHYSIOLOGY IN THE UNIVERSITY OF OXFORD. SECOND EDITION, REVISED AND ENLARGED. BHitjj 234 ^lustrations. LONDON: CHARLES GRIFFIN AND COMPANY EXETER STREET, STRAND. 1S90. [All rights reserved.] 'SaHantgne -press BALLANTYNE, HANSON AND CO. EDINBURGH AND LONDON BeMcatefc TO MY REVERED AND BELOVED MASTER, CARL LUDWIG. PBEFACE TO SECOND EDITION. The fact that this little work has run through an edition in a little over a year seems to show that it has met a want felt both by teachers and students of Physiology. The Second Edition has been thoroughly revised in the light of more extended experience as to what may be fairly accom- plished in the limited time at the disposal of candidates for Medical Degrees. The fact that ere long a five years' course of study will be demanded from all medical students leads one to hope that more time will be devoted in the future to the study of Practical Physiology. The exercises for advanced students, and for those aspiring to Honours Degrees in Medicine and Science, have been put in small type, either in the general text or as " Additional Exercises." A considerable number of new exercises have been added both in the Chemical and Experimental Sections, and some of those in the first edition have been recast. In connection with the Chemical Section, I am indebted to Professor Drechsel's Anlei- tung zur Darstellung plujsiologisch-chemischer Praeparate, and to Pbhmann's Anleitung zum chemischen Arbeiten. For some of the experimental exercises I have to thank my friends Professors Kiihne of Heidelberg and Fredericq of Liege. Vlll PREFACE. As regards the Illustrations, I have again to express my obli- gations to Professor Fredericq, and further, to Messrs. Laurent and Oh. Yerdin of Paris, Rothe of Prague, Zeiss of Jena, Her- mann and Pfister of Berne, Gibbs, Cuxson, & Co., and the Cam- bridge Scientific Instrument Co. A considerable number of engravings, from original drawings and tracings, have also been added, increasing the total number of illustrations from 142 in the first to 234 in the present edition. WILLIAM STIRLING. Physiological Laboeatoey, The Owens College,, Manchester, Sep.tew.bcr 1890. CONTENTS. LESSON I. II. III. IV. V. VI. VII. VIII. IX. X. XI. XII. XIII. XIV. XV. XVI. XVII. XVIII. XIX. XX. XXI. XXII. XXIII. XXIV. PART I— CHEMICAL PHYSIOLOGY. THE PROTEIDS . . . . . . . . THE ALBUMENOIDS AND SOME NITROGENOUS DERIVATIVES OF PROTEIDS THE CARBOHYDRATES .... FATS, BONE, AND EXERCISES . THE BLOOD— COAGULATION — ITS PROTEIDS THE COLOURED BLOOD-CORPUSCLES — SPECTRA OF HEMOGLOBIN AND ITS COMPOUNDS WAVE-LENGTHS — DERIVATIVES OF HEMOGLOBIN — ESTIMATION OF HEMOGLOBIN SALIVARY DIGESTION GASTRIC DIGESTION PANCREATIC DIGESTION THE BILE GLYCOGEN IN THE LIVER MILK, FLOUR, AND BREAD MUSCLE .... SOME IMPORTANT ORGANIC SUBSTANCES THE URINE THE INORGANIC CONSTITUENTS OF THE URINE ORGANIC CONSTITUENTS OF THE URINE . VOLUMETRIC ANALYSIS FOR UREA . URIC ACID — URATES — HIPPURIC ACID — KREATININ ABNORMAL CONSTITUENTS OF THE URINE BLOOD, BILE, AND SUGAR IN URINE QUANTITATIVE ESTIMATION OF SUGAR . URINARY DEPOSITS, CALCULI, AND GENERAL EXAMINATION OF THE URINE I-I3 I3-l6 I6-2S 29-33 33-41 42-52 53-65 65-69 69-76 76-82 82-S6 86-89 S9-93 93-95 96-97 97-103 103-109 109-112 112-119 119-12S 128-132 132-135 135-I3S 139-146 X CONTENTS. PART II.— EXPERIMENTAL PHYSIOLOGY. LESSON PAGES XXV. GALVANIC BATTERIES AND GALVANOSCOPE .... I47-150 XXVI. ELECTRICAL KEYS — RHEOCHORD I5°-I55 XXVII. INDUCTION MACHINES — ELECTRODES 155— 158 j XXVIII. SINGLE INDUCTION SHOCKS — INTERRUPTED CURRENT — BREAK EXTRA-CURRENT — HELMHOLTZ's MODIFICATION . . I59-I61 XXIX. PITHING — CILIARY MOTION — NERVE-MUSCLE PREPARATION — NORMAL SALINE 16I-164 XXX. NERVE-MUSCLE PREPARATION — STIMULATION OF NERVE — MECHANICAL, CHEMICAL, AND THERMAL STIMULI . . 1 64- 1 67 XXXI. SINGLE AND INTERRUPTED INDUCTION SHOCKS — TETANUS — CONSTANT CURRENT 167-170 XXXII. RHEONOM — TELEPHONE EXPERIMENT — DIRECT AND INDIRECT STIMULATION OF MUSCLE — RUPTURING STRAIN OF TENDON — MUSCLE SOUND — DYNAMOMETERS .... I7O-171 XXXIII. INDEPENDENT MUSCULAR EXCITABILITY — ACTION OF CURARE — ROSENTHAL'S MODIFICATION — POHL's COMMUTATOR . I 72- 1 75 XXXIV. THE GRAPHIC METHOD — MOIST CHAMBER — SINGLE CONTRAC- TION— WORK DONE 175-182 XXXV. ANALYSIS OF A MUSCULAR CONTRACTION — PENDULUM-MYO- GRAPH — SPRING-MYOGRAPH — TIME- MARKER — SIGNAL . 182-I9O XXXVI. INFLUENCE OF TEMPERATURE, LOAD, AND VERATRIA ON MUSCULAR CONTRACTION IQO-I92 XXXVII. ELASTICITY AND EXTENSIBILITY OF MUSCLE . . . 1 92- 1 93 XXXVIII. FATIGUE OF MUSCLE AND NERVE — ERGOGRAPH . . . 1 94- 1 97 XXXIX. PRODUCTION OF TETANUS — METRONOME — THICKENING OF A MUSCLE 197-201 XL. TWO SUCCESSIVE SHOCKS — ACTION OF DRUGS ON EXCISED MUSCLE 201-203 XLI. DIFFERENTIAL ASTATIC GALVANOMETER — NON-POL ARISABLE ELECTRODES — SHUNT — DEMARCATION AND ACTION CUR- RENTS IN MUSCLE 203-208 XLII. NERVE-CURRENTS — ELECTRO-MOTIVE PHENOMENA OF THE HEART — CAPILLARY ELECTROMETER .... 209 XLIII. GALVANl's EXPERIMENT — SECONDARY CONTRACTION AND TETANUS — PARADOXICAL CONTRACTION — KUHNE's EXPERI- MENT 210-213 CONTENTS. XI LESSON PAQE3 XLIV. ELECTROTONUS — ELECTKOTONIC VARIATION OF EXCITABILITY 2 1 3-2 1 5 XLV. ELECTROTONIC VARIATION OF THE ELECTRO-MOT1VITY — PFLUGER'S LAW OF CONTRACTION — RITTER'S TETANUS . 215-217 XLVI. UNEQUAL EXCITABILITY AND VELOCITY OF NERVE-ENERGY IN A MOTOR NERVE — KUHNE'S GRACILIS EXPERIMENT . 217-220 XLVII. THE FROG'S HEART — BEATING OF THE HEART — EFFECT OF HEAT AND COLD — SECTION OF THE HEART . . . 220-224 XLVIII. GRAPHIC RECORD OF THE FROG'S HEART-BEAT — EFFECT OF TEMPERATURE 224-227 XLIX. STANNIUS'S EXPERIMENT, AND INTRA - CARDIAC MOTOR CENTRE . ........ 228-229 L. CARDIAC VAGUS AND SYMPATHETIC OF THE FROG AND THEIR STIMULATION 229-232 LI. ACTION OF DRUGS AND THE CONSTANT CURRENT ON THE HEART — DESTRUCTION OF THE CENTRAL NERVOUS SYSTEM . - 233_235 LII. PERFUSION OF FLUIDS THROUGH THE HEART — PISTON RECORDER 235-236 LIIL ENDO-CARDIAL PRESSURE — APEX-PREPARATION . . . 237-238 LIV. GASKELL'S CLAMP — HEART-LEVER — TONOMETER . . . 238-242 LV. HEART- VALVES — STETHOSCOPE — CARDIOGRAPH— POLYGRAPH — MEIOCARDIA — REFLEX INHIBITION OF THE HEART . 242-248 LVI. THE PULSE — SPHYGMOGRAPHS — SPHYGMOSCOPE — PLETHYS- MOGRAPH 248-251 LVII. RIGID AND ELASTIC TUBES — THE PULSE- WAVE — SCHEME OF THE CIRCULATION — RHEOMETER . . . . 252-256 LVIII. CAPILLARY BLOOD- PRESSURE — LYMPH HEARTS — BLOOD- PRESSURE AND KYMOGRAPH 256-262 LIX. MOVEMENTS OF THE CHEST WALL — ELASTICITY OF THE LUNGS — HYDROSTATIC TEST 262-265 LX. VITAL CAPACITY — EXPIRED AIR — PLEURAL PRESSURE — BLOOD- GASES 266-26S LXI. LARYNGOSCOPE — VOWELS 26S-27O LXII. REFLEX ACTION — ACTION OF POISONS — KNEE-JERK . . 27I-274 LXIII. NERVE ROOTS — REACTION TIME 274-276 LXIV. FORMATION OF AN IMAGE — DIFFUSION — ABERRATION — ACCOMMODATION — SCHEINER's EXPERIMENTS — NEAR AND FAR POINTS — PURKINJE'S IMAGES — PHAKOSCOPE— ASTIG- MATISM—PUPIL 276-2S3 Xll CONTENTS. LESSON PAGES LXV. BLIND SPOT — FOVEA CENTEALIS — DIEECT VISION — CLEEK- MAXWELL'S EXPEEIMENT — PHOSPHENES — RETINAL SHADOWS 283-288 LXVI. PEEIMETET — IEEADIATION — IMPERFECT VISUAL JUDGMENTS 288-293 LXVII. KUHNE'S AETIFICIAL EYE — MIXING COLOUE SENSATIONS — COLOUE BLINDNESS 293-3OI LXVIII. THE OPHTHALMOSCOPE ....... 302-304 LIX. TOUCH, SMELL, TASTE, HEAPING ..... 304-308 APPENDIX 309 INDEX . . . . 317 LIST OF ILLUSTRATIONS- FIQ. I. 2. 3- 4- 5- 6. 7- 8. 9- io. ii. 12. 13- 14. IS- 16. 17. 18. 19. 20. 21. 22. S3- 24. 25- 26. 27. 28. 29. 3°- 31- 32. 33- 34- 35- Gamgee's apparatus for coagulation temperature Exsiccator. (Gscheidlen.) .... Hot-air drying oven. {Gscheidlen.) Apparatus for fractional heat coagulation. (Halliburton.) Tyrosin. (Stirling.) Potato starch Potato starch viewed with crossed Nicols. (Stirling.) Phenyl-glucosazon. (V. Jaksch.) .... Laurent's polarimeter. (Laurent. ). "Wild's polaristrobometer. (Hermann and Pfister.) Interference lines, seen with fig. 10 Gad's experiment. (Stirling, after Gad.) Apparatus for obtaining pure serum. (Drechsel.) . Bernard's apparatus for estimating sugar. (Stirling.) Incineration of a deposit. (Gscheidlen.) Gower's haemocytorneter ..... Rat's haemoglobin crystals. (Stirling.) . Spectroscope. (Browning.) Platinum wire and support for sodium flame. (Gscheidlen.) Spectra of haemoglobin. (Landois and Stirling.) Absorption by oxy-haemoglobin. (Rollett.) Absorption by reduced haemoglobin. (Rollett. ) Hermann's haematoscope. (Rollett.) Spectra of derivatives of haemoglobin. (Landois and Stirling.) Haemochromogen apparatus. (Stii'ling.) Spectrum of methaemoglobin. (V. Jaksch.) Spectroscope for wave-lengths. (Landois and Stirling. ) "Wave-lengths of haemoglobin and its compounds. (Prey cr and Gamgee Spectra of derivatives of haemoglobin. (Preycr and Gamgee.) Haemin crystals. (V. Jaksch.) Haemoglobinometer of Gowers Fleischl's hsemometer Bizzozero's chromo-cytometer . Several parts of fig. 33 Micro-spectroscope of Zeiss PAGF 4 11 12 12 16 18 19 22 26 27 28 30 38 40 4i 42 44 44 45 46 47 47 48 50 51 51 S3 54 55 57 58 59 60 61 64 XIV LIST OF ILLUSTRATIONS. FIG. 36. Part of fig. 35. (Zeiss.) . 37. Saliva and buccal secretion. ( V. Jaksch 38. Digestion bath. (Stirling.) 39. Ktihne's dialyser. (Stirling.) . 40. Crystals of cbolesterin. (Stirling.) 41. Double walled funnel. (Gscheidlen.) 42. Milk and colostrum. (Stirling.) 43. Porous cell for filtering milk. (Stirling. 44. Lactoscope ..... 45. Kreatin. (Brunton.) 46. Urinometer. (Landois and Stirling.) 47. Deposit in acid urine. (Landois and Stirling.) 48. Deposit in alkaline urine. (Landois and Stirling 49. Stellar phosphate. ( V. Jaksch.) 50. Triple phosphate ...*.. 51. Triple phosphate. (V. Jaksch.) 52. Burette meniscus 53. Erdmann's float 54. Urea and urea nitrate. (Landois and Stirling.) 55. Urea oxalate ....... 56. Apparatus for decomposing urea 57. Steele's apparatus for urea .... 58. Hiifner's apparatus. ( V. Jaksch. ) . 59. Gerard's urea apparatus. (Gibbs, Cuxson & Co.) 60. Ureameter of Doremus. (Southall.) 61. Uric acid . . . . . 62. Uric acid 63. Urate of soda 64. Hippuric acid. (Landois and Stirling.) 65. Kreatinin zinc-chloride. (Landois and Stirling.) 66. Esbach's tube. (V. Jaksch.) .... 67. Johnson's picro-saccharimeter 68. Einhorn's fermentation saccharometer. (Stirling, 69. Sacchar-ureameter. (Gibbs, Cuxson & Co.) . 70. Oxalate of lime 71. Acid urate of ammonium. (V. Jaksch.) 72. Cystin ..... 73. Leucin and tyrosin . 74. Daniell's cell. (Stirling.) 75. Grove's cell .... 76. Bichromate cell 77. Detector. (Elliott.) 78. Du Bois Reymond's friction key 79. Scheme of 78. (Stirling.) 80. Scheme of 78. (Stirling. ) , 81. Plug key .... 82. Morse key. (Stewart and Gee. ) LIST OF ILLUSTRATIONS. XV PAGE FIG. 83. Spring key. {Elliott.) *52 84. Simple rheochord. {Stirling.) I53 85. Rheochord. (Landois and Stirling.) IS4 86. Reverser. {Elliott.) • • IS5 87. Induction coil. {Elliott.) XS6 88. Vertical inductorium x57 89. Hand-electrodes. {Stirling.) • x57 90. Du Bois electrodes x58 91. Break extra-current. {Stirling. ) l6° 92. Helmholtz's modification l6x 93. Frog's leg-muscles. {Ecker. ) x63 94. Frog's sciatic nerve. {Ecker. ) • l63 95. Nerve-muscle preparation l65 96. Straw-flag. {Stirling.) l66 97. Scheme for single induction shocks. {Stirling.) 167 98. Scheme of constant current. {Stirling.) i68 99. Frog's sartorius and thigh muscles. {Ecker. ) 169 100. Rheonom. {Stirling.) x7° 101. Pohl's commutator. {Elliott.) x73 102. Scheme of curare experiment x74 103. Revolving cylinder x76 104. Scheme of moist chamber. {Stirling.) 177 105. Muscle curve. {Stirling.) *79 106. Muscle curve. {Stirling. ) l8° 107. Crank myograph. {Stirling.) 1S1 108. Pendulum myograph l83 109. Pendulum myograph curve. {Stirling.) i84 no. Spring myograph l84 in. Revolving drum l85 112. Time-marker. {Stirling.) i85 113. Electric signal. (Stirling.) l86 114. Chronograph. {Cambridge Scientific Instrument Co.) . . . .186 115. Chronograph. {Verdin.) l87 116. Chronograph writing horizontally. {Marey.) i88 117. Simple myograph. {Mareij.) . *88 118. Myograph. {Fredcricq.) l89 119. Effect of temperature on muscle curve. {Stirling.) . . . .190 120. Muscle curve with load. {Stirling.) 191 121. Veratria curve. {Stirling.) I92 122. Elasticity of a frog's muscle. {Stirling.) 193 123. Elasticity of india-rubber. {Stirling.) 193 124. Fatigue curve. (Stirling.) J94 125. Pfliiger's myograph x95 126. Fatigue curve. (Stirling.) J96 127. Scheme for tetanus. (Stirling.) 197 128. Tetanus curves. (Stirling.) 198 129. Tetanus interrupter. (Stirling.) . . 198 XVI LIST OF ILLUSTRATIONS. FIG. I3O. 131- 132. 133- 134. 135- 136. *37- 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150. IS1- 152. 153- 154- iSS- 156. i57. 158. 159- 160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173- 174. 175- 176. Metronome. (Verdin.) Magnetic interrupter. {Cambridge Scientific Instrument Co Marey'3 registering tambour Pince myographique. {Marey.) .... Marey's tambour, writing-lever cut short Effects of successive shocks on muscle. {Stirling. ) Wild's apparatus. {Stirling.) .... Thomson's galvanometer. {Elliott.) Lamp and scale for 137 ...... Non-polarisable electrodes Shunt. {Elliott.) Scheme for galvanometer. {Stirling. ) . Brush electrodes. {V. Fleischl.) .... D'Arsonval's electrodes. {Verdin.) Non-polarisable nerve electrodes .... Galvani's experiment. {Stirling. ) Secondary contraction ...... Scheme of secondary contraction. {Stirling. ) Scheme of paradoxical contraction. {Stirling.) . Kiihne's experiment. {Stirling.) .... Scheme of electrotonus. {Stirling. ) Scheme of electrotonus. {Landois and Stirling.) Scheme of electrotonic excitability. {Stirling.) . Scheme of Pfluger's law of contraction. {Stirling.) Scheme for unequal excitability of a nerve. {Stirling Scheme of velocity of nerve-energy. {Stirling.) . Kiihne's gracilis experiment. {Stirling.) Frog's heart from the front. {Ecker.) . Frog's heart from behind. {Ecker.) Simple frog's heart lever Tracing of frog's heart. {Stirling.) Electric time-marker. {Cambridge Scientific Instrument Co Effect of temperature on frog's heart tracing. {Stirling. ) Marey's heart lever Francois-Frank's lever for heart of tortoise. {Verdin.) Scheme of frog's vagus. {Stirling.) Vagus curve of frog's heart. {Stirling.) Scheme of frog's sympathetic. {Oaskell.) . Support for frog's heart. {Stirling.) . Staircase heart-tracing Kronecker's frog's heart cannula .... Heart-tracing during perfusion. {Stirling.) Scheme of Kronecker's manometer. {Stirling.) . Gaskell's clamp. {Stirling.) .... Tracing of auricles and ventricles. {Stirling.) Frog's heart-tracing. {Stirling.) .... Frog's heart-lever. {Stirling.) .... PAGE I99 199 200 200 200 20I 202 204 204 204 205 206 208 208 209 2IO 211 211 212 212 214 214 215 2l6 218 2l8 220 221 221 224 225 225 226 227 227 23O 23I 232 233 234 235 236 237 238 239 239 24O LIST OF ILLUSTRATIONS. XV11 FIG. 177. Scheme of Roy's tonometer. (Stirling.) 178. Tonometer. (Cambridge Scientific Instrument Co.) 179. Marey's cardiograph .... 180. Polygraph of Rothe .... 181. Cardiac impulse tracing. (Knoll.) 182. Rothe's tambour ..... 183. Radial pulse and respirations. (Knoll.) 184. Radial pulse and cardiac impulse. (Knoll. ) 185. Marey's sphygmograph. (Bramwell.) . 186. Sphygmograms. (Marey.) . 187. Dudgeon's sphygmograph 188. Sphygmogram. (Dudgeon.). 189. Ludwig's sphygmograph 190. Gas-sphygmoscope .... 191. Marey's scheme of rigid and elastic tubes 192. Rheometer ...... 193. Capillary pressure apparatus (V. Kries.) 194. Lymph-hearts. (Ecker.) 195. Simple kymograph (made by Verdin) . 196. Nerves in neck of rabbit. (Cyon.) 197. Shielded electrodes as made by Verdin 198. Blood-pressure tracing of dog 199. Blood-pressure tracing of dog. (Stirling.) 200. Francois-Frank's cannula. (Verdin. ) . 201. Marey's respiration double tambour 202. Stethographic tracing. (Stirling.) 203. Marey's stethograph. (Verdin.) 204. Stethographic tracing. (Knoll.) . 205. Midler's valves. (Stirling.) . 206. Hey wood's experiment. (Stirling.) 207. Gases collected over mercury. (Gscheidlen. 208. View of larynx ..... 209. Larynx during vocalisation . 210. Konig's apparatus ..... 2x1. Neuramcebometer. (Obersteiner. ) 212. Scheiner's experiment .... 213. Diffusion. (Hclmholtz.) 214. Phakoscope ...... 215. Mariotte's experiment .... 216. Mariotte's experiment (another way) . 217. Blind spot. (Helmholtz.) 218. Bergmann's experiment. (Hclmholtz.) 219. Disc for Talbot's law. (Hclmholtz.) 220. Priestley Smith's perimeter . 221. Irradiation. (Helmholtz.) 222. Irradiation. (Hclmholtz.) 223. Irradiation. (Helmholtz.) . PAGE 241 241 244 245 246 246 247 247 249 249 250 250 250 251 254 255 257 257 258 259 259 260 261 262 263 263 264 264 266 267 267 269 269 270 275 279 280 281 283 284 284 286 287 288 289 290 290 XViil LIST OF ILLUSTRATIONS. 224. Imperfect visual judgments .... 225. Zollner's lines . . ... 226. Perception of size. (Helmholtz. ) . 227. Spiral disc for radial movement. (Helmholtz. ' 228. Kiihne's artificial eye, as made by Jung 229. Rothe's rotatory apparatus .... 230. Disc for contrast. (Helmholtz.) . 231. Disc for simultaneous contrast. (Helmholtz.) 232. Ragona Scina's experiment. (Mood. ) . 233. Michel's carriage for rabbit. (Stirling.) 234. Aristotle's experiment ..... PAGE 291 291 292 293 294 29s 297 298 299 303 3°4 PRACTICAL PHYSIOLOGY. PART L— CHEMICAL PHYSIOLOGY. LESSON I. THE PROTEIDS. The group of proteids includes a large number of compounds, which, in their general characters, present a greater or less re- semblance to white of egg or albumin. In nature they occur only as constituents or products of living organisms. They occur in small amount in plants (except in the seeds), but in animals they form a large part of most of the solids and fluids of the body, existing in some cases in a solid, and in others in a fluid form. The bile, urine, and sweat are the only animal fluids which normally do not contain proteids. They all consist of C, H, 0, and N ; most of them also contain S, and a few of them contain in addition P. Their elementary composition varies as follows : — c. H. N. S. 0. From 50 6.8 154 0.4 22.8 per cent. To 55 7-3 18.2 5-o 24.1 Most of them are amorphous, a very few only occurring in a crystalline form. Most of them are colloids, and do not diffuse readily through animal membranes. When decomposed, they yield a very large number of other bodies, so that their consti- tution is exceedingly complex. In the human body, after under- going a series of metabolic changes, they are chiefly excreted 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. [I. The White of Egg may be taken as the Type. 1. Preparation of a Solution. — Place the 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 mem- branes, and thus liberate the albumin. Add twenty volumes of distilled water, and place the mixture in a flask. Shake well until it froths freely. Cork the flask, and invert it, mouth downwards, over a porcelain capsule ; the membranes will rise to the surface, and, after a time, if the cork be gently withdrawn to allow the fluid to escape, a comparatively clear, or slightly opalescent, fluid will be obtained. The opalescence is due to the precipitation of a small quantity of globulins. 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 alkaline, neutralise it. This solution contains about 5 per cent, of albumin, and diffuses slowly through animal membranes. General Reactions. — (A.) Colour Tests. (a.) Xanthoproteic Reaction. — To some of the fluid in a test- tube add strong nitric acid = a precipitate, which on being boiled turns yellow. Allow the liquid to cool, and add strong ammonia = an orange precipitate or colour. (b.) To another portion add Millon's reagent = a whitish pre- cipitate which becomes reddish on boiling. 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 solu- tion thus obtained add two volumes of water. Allow it to stand, and afterwards decant the clear fluid ; or take one part of mer- cury, 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. (c.) Biuret Reaction. — To a third portion add a drop or two of very dilute solution of cupric sulphate, and then a solution of caustic soda (or potash) = a violet colour. The reaction occurs more quickly if heat is applied. (B.) Precipitation in the Cold. (d.) The solution is precipitated by (i.) Lead acetate, (ii.) Mer- curic chloride, (iii.) Picric acid. (e.) Make a portion strongly acid with acetic acid, and add potassic ferrocyanide = a white precipitate. (/.) By hydrochloric acid in a solution saturated with common salt. I.] THE PROTEIDS. 3 (g.) Precipitate a portion with meta-phosphoric acid. N.B. — Peptones are not precipitated by (e.) and (/.). (C.) Coagulation by Heat. (h.) Heat the fluid to boiling, and then add, drop by drop, dilute acetic acid until a flaky coagulum separates. Filter. (i.) Heat a portion of the neutral solution faintly acidulated with acetic acid = a coagulum at about 70° C. Unless it be acidulated the albumin does not coagulate. (./.) Boil and add dilute nitric acid = a white or yellowish coagulum. (k.) Mix some of the solution with an equal volume of a satu- rated solution of sodic sulphate, add acetic acid until the reaction is strongly acid, and boil = coagulation. This method and the foregoing (i.) are used for separating the albumin in a liquid containing it. (D.) (/.) Non-Diffusibility of Proteids. — Place some of the solu- tion either in a dialyser or in a sausage-tube made of parch- ment-paper, and suspend the latter by means of a glass rod thrust through the tube just below the two open ends, as in fig. 39, in a tall glass jar or beaker filled with distilled water, so that the two open ends are above the surface of the water. The salts will diffuse readily (test for chlorides by nitrate of silver and nitric acid), but on applying any of the above tests no proteid will be found in the diffusate. (Peptones, however, are very diffusible through animal membranes.) (E.) Make also the following experiments : — (m. ) Reaction of Adamkiewicz. — To a solution of white of egg add glacial acetic acid, and heat to get it in solution ; gradually add concentrated sul- phuric acid = a violet colour. (n.) Liebermann's Reaction. — Wash finely powdered albumin first with alcohol and then with cold ether, and heat the washed residue with concen- trated hydrochloric acid = a deep violet-blue colour. This is best done in a white porcelain capsule, or on a filter-paper in a funnel ; in the latter case, the boiling acid is poured gently down the side of the filter-paper. 2. Presence of Nitrogen and Sulphur in Albumin. (a.) Place some powdered dried albumin in a reduction tube, and into the mouth of the tube insert (1) a piece of red litmus paper, and (2) a lead acetate paper. On heating the tube, the former becomes blue from the escape of ammonia, which can also be smelt, and the latter black from the formation of lead sulphide. (6.) Heat some dry proteid with excess of soda-lime in a hard dry tube, when ammonia vapour is evolved. (c.) Place a few grains of the dry proteid, 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 PRACTICAL PHYSIOLOGY. [I- 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 pre- cipitate 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 heat = a brownish colouration, due to lead sulphide. 3. Determination of Temperature of Coagula- tion (fig. i). — "A glass beaker containing water is placed within a second larger beaker also containing water, the two being separated by a ring of cork. Into the water contained in the inner beaker there is immersed a test-tube, in which is fixed an accu- rately graduated thermometer, provided with a long narrow bulb. The solution of the proteid, of which the temperature of coagulation is to be determined, is placed in the test-tube, the quantity being just sufficient to cover the thermometer bulb. The whole apparatus is then gradually heated, and the experi- menter notes the temperature at which the liquid first shows signs of opalescence" (Gamgee). 4. Circumstances Modifying the Coagulating Temperature. — Place 5 cc. of the solution of albu- min in each of three test-tubes, colour them with a neutral solution of litmus, and label them A, B, C. To A add a drop of very dilute acetic acid (o. 1 per cent, acetic acid diluted five or six times) ; to B add a very dilute solution of caustic soda (0.1 per 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 coagu- lation occurs first in A, next in C, and last of all in B, the alkaline solution. Fig. i. — Apparatus for De- termining the Coagula- tion Temperature of Proteids. CLASSIFICATION AND PROPERTIES OF THE CHIEF PROTEIDS. 5. I. Native Albumins are soluble in water, and are not pre- cipitated by alkaline carbonates, sodic chloride, or very dilute acids. They are coagulated by heat at 65° to 73° O, although the temperature varies considerably with a large number of con- ditions. When dried at 40° C. they yield a clear yellow, amber- coloured, friable mass, "soluble albumin," which is soluble in water. (1.) Egg- Albumin. — Prepare a solution as directed in Lesson I. 1. In addition, perform the following experiments : — (a.) Evaporate some of the fluid to dryness at 400 C. over a water-bath to obtain " soluble albumin." Study its characters, notably its solubility in water. This solution gives all the I.] THE PROTEIDS. 5 tests of egg-albumin. It is more convenient to purchase this substance. (b.) The fluid gives all the general pi^oteid reactions. (c.) Precipitate portions of the fluid with strong mineral acids, including sulphuric and hydrochloric acids. (d.) Precipitate other portions by each of the following : — Mercuric chloride, basic lead acetate, tannic acid, alcohol, picric acid. (e.) Take 5 cc. of the fluid, add twice its volume of o. 1 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 not precipitated on saturation with sodic chloride or magnesic sulphate, but it is completely precipitated by ammonium sulphate (NH4)2S04 (compare "Globulins"). (g.) A solution containing 1-3 per cent, of salts coagulates at about 5 6° C. (2.) Serum- Albumin. — Dilute blood-serum until it has the same specific gravity as the egg-albumin solution. Neutralise the solu- tion with very dilute acid until a faint haziness is obtained. Repeat all the tests for egg-albumin, but, in addition, note that the two solutions differ in the following respects : — EGG-ALBUMIN". (a.) Readily precipitated by hydrochloric acid, but the pre- cipitate is not readily soluble in excess. (b.) A non-alkaline solution is coagulated by ether. (c.) The precipitate with nitric acid is soluble with diffi- culty in excess of the acid. (d.) The precipitate obtained by boiling is but slightly solu- ble in boiling nitric acid. [(e.) When injected under the skin, or introduced in large quantities into the stomach or rectum, it is given off by the urine.] SERUM-ALBUMIN. (a.) It is also precipitated by hydrochloric acid, but not so readily, while the precipitate is soluble in excess. (/;.) It is not coagulated by ether. (c.) The corresponding pre- cipitate is much more soluble in excess of acid. (d.) The corresponding pre- cipitate is soluble in strong nitric acid. [(e.) When injected under the skin, it does not appear in the urine.] [(/.) Its solution is not pre- cipitated by MgS04, but is completely precipitated by (NII4),S04.] [Gives the same reactions as in (/.).] 6 PRACTICAL PHYSIOLOGY. [I- 6. II. Globulins are insoluble in pure water, but are soluble in weak solutions of neutral salts — e.g., NaCl, MgS04, (NH4)2S04 — but insoluble in saturated ones. Their solutions in these salts are coagulated by heat. They are soluble in dilute acids and alkalies, yielding acid- and alkali-albumins respectively. Most of them are precipitated from their saline solution by crystals of sodic chloride. (A.) Precipitated by saturation with sodic chloride. (i.) Myosin, see "Muscle." (2.) Serum-G-lobulin. — It is insoluble in water, readily soluble in dilute saline solutions (NaCl, MgS04, (NH4)2S04). Its solutions give the general reactions for proteids. Its NaCl solution coagu- lates at about 750 C. (a.) Neutralise 5 cc. of blood-serum with a few drops of dilute sulphuric acid (o. 1 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. (b.) Boil a portion of the neutralised fluid = coagulation. (c.) To 5 cc. of blood-serum in a test-tube add an excess of crystals of magnesic sulphate, and shake briskly for some time. On standing, a white precipitate of serum-globulin falls. Pour off the supernatant fluid, and observe that the precipi- tate is redissolved on the addition of water. Filter the super- natant fluid and test it for other proteids, which it still contains — viz., serum-albumin. (d.) Take 5 cc. of blood-serum and pour a saturated solution of magnesic sulphate down the side of the glass to form a layer at the bottom of the tube. Where the two fluids meet, there is a copious white deposit of serum-globulin. (e.) Treat another portion of blood -serum to saturation with crystals of sodic chloride or neutral ammonic sulphate, and observe the same result = white precipitate of serum-globulin. (f.) Take another portion of blood-serum, precipitate the serum- globulin with magnesic sulphate, and filter. To the filtrate add powdered sodic sulphate in excess, which gives a further precipi- tate. The filtrate still gives the reactions for proteids. (3.) Fibrinogen, see "Blood." (B.) Not precipitated by saturation with sodic chloride. (4.) Vitellin. — Shake up the yolk of an egg with water and ether, as long as the washings show a yellow colour. (Keep this fluid.) Dissolve the white residue in a 10 per cent, sodic chloride solution. Pour it into a large quan- tity of water, slightly acidulated with acetic acid = copious white precipitate of impure vitellin. (a.) Dissolve some of the precipitate in a very weak saline solution, and observe that it is not reprecipitated by saturation with sodic chloride. I.] THE PROTEIDS. 7 (b.) Test some of the weak saline solution = coagulation about 750 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. 7. III. Derived Albumins are insoluble in pure water and in solutions of sodic chloride, but readily soluble in dilute hydrochloric acid and dilute alkalies. The solutions are not coagulated by heat. (1.) Alkali- Albumin or Alkali- Albuminate — Preparation of Solution. — Prepare a 5 per cent, solution of egg-albumin, as directed in Lesson I. 1. (a.) To the egg-albumin add a few drops of solution of caustic soda or potash (o. 1 per cent.), and heat it gently for a few minutes = alkali- albumin. Boil the fluid ; it does not coagulate. (b.) Test the reaction ; it is alkaline. (c.) Cool some of the alkali-albumin and colour it with litmus solution. Neutralise it carefully with very dilute acid = a preci- pitate on neutralisation, which is soluble in excess of the acid. (d.) Repeat (c.) ; but, before doing so, add a few drops of sodic phosphate solution (10 per cent.), and note that the alkaline phosphates prevent the precipitation on neutralisation, until at least sufficient acid is added to convert the basic phosphate into acid phosphate. The solution must be decidedly acid before a precipitate is obtained. (e.) Precipitate it by saturating its solution with crystals of common salt or magnesic sulphate. (/.) Lieberkiihn's Jelly is really a strong solution of alkali- albumin. Place some undiluted white of ego- in a test-tube, and add, drop by drop, a strong solution of caustic potash. The whole mass becomes stiff and glue-like, so that the tube can be inverted without the mass falling out. (7.) Its solution gives the general reactions for proteids under 1 (A.). (2.) Casein is regarded as a form of alkali-albumin, and will be referred to again. (See "Milk.") To Prepare Casein. — Dilute 200 cc. of fresh cow's milk with 800 cc. of water, and add dilute acetic acid (.75-1 per cent.). The casein is precipitated, and is then rapidly washed and the water decanted. Keep the fluid for the preparation of lactose (Lesson III. 13). The deposit is pressed in a cloth or press, and is then rubbed up in a mortar, and dissolved in the smallest quantity of .1 per cent, caustic soda. Care must be taken that the fluid does not become alkaline ; it must be mutral. The fluid — at first milky — on being filtered several times becomes clear, but with a slight blue opalesence. Dilute again with water, reprecipitate with acetic acid, and repeat this process twice. The precipitate is washed with water, expressed, and rapidly rubbed up to a fine pulp with 75 per cent, alcohol. It is then washed on a filter, first with alcohol and then with ether, expressed, and allowed to dry in a capsule, taking care to stir it from time to time. 8 PRACTICAL PHYSIOLOGY. [I. It forms a white insoluble powder, which reddens moist blue litmus-paper. It is readily soluble in dilute alkalies and acids. In a solution of .2 per cent, hydrochloric acid and pepsin at 38°-40° C, the solution gradually becomes turbid, casein peptone is found in solution, and a deposit of nuclein is formed. (3.) Acid-Albumin or Syntonin. Preparation. — (A.) To a 5 per cent, solution of egg-albumin acid a few drops of dilute acid {e.g., o. 1 per cent, sulphuric acid, or hydrochloric acid .2 per cent.), and warm gently for several minutes = acid-albumin. (B.) To finely-minced muscle, free from fat, add ten times its volume of dilute hydrochloric acid (4 cc. of acid in 1 litre of water), and allow it to stand for several hours, taking care to stir it frequently ; filter, the filtrate is a solution of 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 .1 per cent. HC1, and after a time neutralising the solution with sodic carbonate. Use the clear filtrate from (A.) or (B.) for testing. (a.) The reaction is acid. (b.) Boil the solution; it does not coagulate. (c.) Add some litmus solution, and neutralise another portion with very dilute potash or soda. A precipitate occurs, which is soluble in excess of the alkali. (d.) Repeat (c), but add sodic phosphate before neutralising; the syntonin is precipitated when the fluid is exactly neutralised ; so that sodic phosphate does not interfere with its precipita- tion. (e.) Add strong nitric acid = a precipitate which dissolves on heating, producing an intense yellow colour. (/.) It also gives the biuret test, and that with Millon's reagent (Lesson I. 1). (g,) It is precipitated from its NaCl solution by NaCl, but is dissolved by concentrated HC1. (h.) It is insoluble in NaCl. (i.) Boiled with lime-water = partial coagulation. 8. IV. Fibrin is insoluble in water and in weak solutions of common salt. When prepared from blood and washed, it is a white, fibrous, soft, and very elastic substance, which exhibits fibrillation under a high magnifying power (see " Blood "). (a.) Place some well- washed fibrin in a test-tube, add some 0.1 per cent, hydrochloric acid, and observe that the fibrin swells up and becomes clear in the cold, but does not dissolve. (b.) Place a test-tube as in (a.) on a water-bath at 6o° C. for L] THE PROTEIDS. 9 several hours ; filter, and test the filtrate for acid-albumin by neutralisation with very dilute potash. (c.) For the effect of a dilute acid and pepsin (see "Digestion "). (d.) It decomposes hydric peroxide, and turns freshly-pre- pared tincture of guaiacum blue (see " Blood "). (e.) Place a very dilute solution of cupric sulphate in a test- tube, add a flake of fibrin. The latter becomes greenish, while the fluid is decolorised. On adding caustic potash, the flake becomes violet. This is merely the biuret reaction common to proteids generally. (/.) Steep some fibrin in 10 per cent, sodic chloride for two days. A small part is dissolved ; prove by boiling the fluid = coagulation. ({/.) When boiled = coagulated proteid. 9. V. Coagulated Proteids are insoluble in water, dilute acids, and alkalies, and are dissolved when digested at 35° to 400 C. in gastric juice (acid medium), or pancreatic juice (alkaline medium), forming peptones. They give Millon's reaction. Preparation. — Boil white of egg hard, and chop up the white. (a.) Test its insolubility in water, dilute acids, and alkalies. (&.) 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 water, and test it with Millon's reagent. (d.) For the effect of the digestive juices see " Digestion." 10. VI. Peptones are exceedingly soluble in water. Their solu- tions are not precipitated by sodic chloride, acids, or alkalies, nor are they coagulated by heat. They are precipitated by tannic acid, and with difficulty by a large excess of absolute alcohol. Preparation (see " Digestion "). — For applying the tests dis- solve a small quantity of Darby's fluid meat in warm water, and filter, or dissolve some peptone in water. The latter can be bought as a commercial product. The peptone of commerce usually contains only about 50 per cent, or less of peptone. (a.) Boil a portion; it is not coagulated. (b.) Xanthoproteic Reaction. — To another portion add strong nitric acid, and boil = a faint yellowish colour, and rarely any previous precipitate ; allow it to cool, and add strong ammonia = orange colour. (c.) Acidify a third portion 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 IO PRACTICAL PHYSIOLOGY. [L lead acetate. Each of these causes a precipitate. In the case of picric acid the precipitate disappears on heating, and reappears on cooling. (e.) Biuret Reaction. — To another portion add a few drops of very dilute solution of cupric sulphate, and then caustic soda (or potash) = a rose colour ; on adding more cupric sulphate, it changes to a violet. (/.) Biuret Reaction. — To another portion add a drop or two of Fehling's solution = a rose colour ; on adding more Fehling's solution it changes to violet. (vn 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. (6.) With iodine and sulphuric acid occasionally a blue reaction is obtained. (c.) Methyl-violet and gentian violet give a rose-pink reaction with the waxy parts, while others, i.e., the healthy parts of an organ, give different shades of blue or purple. 12. The Albumoses. — In the peptic and tryptic digestion of proteids these bodies are formed as intermediate products. In peptic digestion syntonin is first formed, and finally peptone. Between the two is the group of albumoses. There are several of them, and they were formerly grouped together as hemi- albumose. (See "Digestion.") Witte's peptone usually con- tains in addition to peptone sufficient hemi-albumose to enable one to obtain the reactions for this body. Dissolve some of this I.] THE PROTEIDS. I I body in warm water, or use a solution of pure hemi-albumose. (See "Gastric digestion.") (a.) The substance is soluble in water, is not coagulated by heat, and is precipitated by saturation with pounded neutral ammonium sulphate. (b.) Add nitric acid = a white precipitate which dissolves with heat (yellow fluid) and reappears on cooling. Divide the heated yellow fluid into two portions, and run cold water from the tap on one tube, and observe that the precipitate reappears. This is a characteristic reaction. (c.) It, like peptone, gives a rosy-pink with the biuret test. (d.) It is precipitated by acetic acid and ferrocyanide of potas- sium, but the precipitate disappears on heating, and reappears on cooling. (e.) It is precipitated by acetic acid and saturation with NaCl. The precipitate disappears on heating, and reappears on cooling. 13. To Obtain Comparatively Pure Hemi-Albumose. — Precipitate Witte's peptonuria siccum with powdered NaCI ami acetic acid, dissolve the precipitate- in water, and purify it by repre- cipitating it as above several times. Filter the hot fluid, concentrate it, and free it from the salt by dialy- sis. Evaporate the fluid to a thick syrup, precipitate it by alcohol. Dry the precipitate over H0SO4 in an exsiccator (fig. 2), and then in a hot-air oven (fig. 3), at 1050 C. 14. Fractional Heat Coagula- tion, e.g., of blood-serum. — This almost explains itself. The serum or other fluid containing proteid is heated until a flocculent preci- pitate occurs. This is filtered off. The filtrate is again heated to a higher temperature, until a simi- lar precipitate appears. This pre- cipitate is filtered off, and the above process repeated, until the liquid is free of proteid. The arrangement shown in fig. 1 may be used, but the rise of temperature takes place rather too slowly, and it is difficult to maintain the temperature constant for a considerable length of time when one is investigating a large number of fluids. The following apparatus used by Halliburton (fig. 4) is more convenient. " A glass flask supported on a stand; down its neck is placed a test-tube, in which again is placed the liquid under investigation in sufficient quantity to cover the bulb of a thermometer placed in it. The flask is kept filled with hot water, and this water is constantly flowing." It enters by (a), passing to the bottom of the flask, and leaves at (b). The water is heated by passing through a coil of tubing contained in a copper vessel, not Fig. 2. — Exsiccator for Drying a Precipitate over Sulphuric Acid. b. Glass bell-jar. covering vessel with sulphuric acid (c), and support (rf) for the deposit or precipitate. 12 PRACTICAL PHYSIOLOGY [I- unlike Fletcher's hot-water apparatus. The fluid to be tested must be well stirred by the thermometer during the progress of the experiment. In carrying out the experiment the following precautions are necessary, Fig. 3.— Hot- Air Oven. G. Gas regulator ; E. Thermometer. 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. Fid. 4. — Apparatus of Halliburton for Fractional Heat Coagulation of Proteids. T. Tap for water ; C. Copper vessel with spiral tube ; a. Inlet, and 6. Outlet-tube to the flask ; t. Test-tube, with fluid and thermometer. Use a 2 per cent, solution of 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 II.] THE ALBUMENOIDS, ETC. I 3 of the liquid is tested by sensitive litmus papers. The liquid must be kept at a given temperature for at least five niiuutes, to ensure complete precipitation of the proteid at that temperature. On heating certain solutions containing certain proteids, as the temperature 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 varies with a large number of conditions. Not only have dif- ferent proteids different coagulating points, which, however, can hardly in the light of recent researches be called " specific coagulation temperatures," but 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 raised by dilution. The effects of salts and acids in altering the coagulation point are well known. LESSON II. THE ALBUMENOIDS, AND SOME NITROGENOUS DERIVATIVES OP PROTEIDS. The group of albumenoids includes a number of bodies which in their general characters and elementary composition closely resemble the true proteids. They are mostly amorphous non- crystalline bodies, and some of them are derived from proteids by the metabolism of the latter. Some of them contain sulphur, and others do not. The decomposition-products resemble the decomposition-products of true proteids. 1. I. Gelatin is obtained by the prolonged boiling of connec- tive tissues, e.g., tendon, ligaments, bone, and from the hypo- thetical substance " Collagen," of which fibrous tissue is said to consist. Preparation of a Solution. — Use commercial gelatin. Make 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.) Note its characters when dry. It is insoluble, but swells up in about six times its volume of cold water. (b.) After a time heat the gelatin swollen up in water; it dissolves. Allow it to cool ; it gelatinises. (B.) With General Proteid Tests (§ 1, A., B.). (c.) Xanthoproteic Test. — Add nitric acid = a yellow colour with no previous precipitate ; the fluid becomes orange on adding ammonia. (i7.) Millon's Reagent = pinkish-red precipitate. 14 PRACTICAL PHYSIOLOGY. [H. (e.) Biuret Test = violet colour. (/.) It is not precipitated by acetic acid and potassic ferro- cyanide (unlike albumin). (g.) It is not coagulated by heat (unlike albumin). (h.) It is not coagulated by boiling with sodic sulphate and acetic acid (unlike albumin). (C.) Special Reactions. (?'.) It is not precipitated by acids (acetic or hydrochloric), or alkalies, or lead acetate. (j.) Add mercuric chloride = white precipitate, insoluble in excess. (Jc.) Add tannic acid = copious white precipitate, insoluble in excess. (/.) Add picric acid (saturated solution) = yellowish-white pre- cipitate, which disappears on heating and reappears on cooling. (in.) It is also precipitated by alcohol and by platinic chloride. 2. II. Chondrin is derived by prolonged boiling from the matrix of cartilage, which is supposed to consist of the hypothetical sub- stance " Chondrogen. " Preparation. — Costal cartilages freed of their perichondrium and cut into small pieces are boiled for several hours in water, when an opalescent 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 "Bile." 4. IV. Elastin occurs in elastic tissue, ligamentum nuchse, and liofamenta subflava, &c. It is prepared from the fresh ligamentum nuchae of an ox by boiling it suc- cessively in alcohol, ether (to remove the fats), water (to remove the gelatin), and finally in acids and alkalies. This substance must be previously prepared so that the student can test its reactions (a. ) It is insoluble in water, but is soluble in strong caustic soda. (b. ) It gives the xanthoproteic test. (c.) It is precipitated from a solution by tannic acid. 5. V. Keratin occurs in epithelial structures, e.g., horn, hoof, hairs, and nails. It is characterised by the large amount of sulphur it contains ; part of the latter is loosely combined. It resists putrefaction for a long time. (a.) Burn a paring of horn, and note the characteristic smell. (b.) Heat a paring of nail or horn with strong caustic soda and lead acetate = black or brown colouration, due to the formation of lead sulphide. (c.) Test for the presence of sulphur by the method, Lesson I. 2. II] THE ALBUMENOIDS, ETC. I 5 Some Nitrogenous Derivatives of the Foregoing, or Nitrogenous Extractives. 6. Urea (CON2H4). — This substance is fully considered under " Urine," but a few of its characteristic reactions are stated here. (a.) To some crystals add caustic soda and heat = vapour with odour of ammonia. (b.) Heat some in a test-tube, and test the residue with the biuret reaction. (c.) Examine its crystalline form, when a watery and an alco- holic solution are evaporated on a slide. (d.) It gives a white precipitate with mercuric nitrate. (e.) Add NaCl and then mercuric nitrate = no precipitate, unless the mercuric nitrate be added in excess. (/.) Add hypobromite of soda = evolution of C02 and N. 7. Uric Acid (C5H4N403).— See also " Urine." Use one of the alkaline urates. (a.) Murexide Test.— To the powder, or if in solution, eva- porate, and to the dry residue on a porcelain capsule add nitric- acid, and heat to about 40° C. =a reddish-yellow stain of alloxan. Cool and add liquid ammonia = purple colour of murexide. 8. For Kreatin and Kreatinin see "Muscle " and "Urine." Leucin or a-Amido-Caproic Acid, C6H13N(X = CH3 (CH2)3, CH(NH.,), CO.OH, and Tyrosin or Paraoxyphenyl-a-Amido- propionicacid,C9HuN03 = C6H4<^2 (NHo)CO.OH.— These two bodies are obtained together from nearly all proteids when the latter are decomposed by the action of acids. The former belongs to the fatty bodies, and is readily obtained from decomposed proteids, and it is formed during pancreatic digestion. Tyrosin belongs to the aromatic group, and is a derivative of benzene (C6H6). 9. Preparation of Leucin and Tyrosin. — Place 2 parts of horn shavings (h-l 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 the 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 resulting precipitate 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 foim crystallises out. i6 PRACTICAL PHYSIOLOGY. [III. The mother-liquor, freed from tyrosin, is treated with hydric sulphide to get rid of the lead, filtered, evaporated, and boiled for a few minutes with freshly precipitated hydrated copper oxide, which 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- posed in water by hydric sulphide, the filtrate when necessary decolorised by boiling with animal charcoal, again filtered and evaporated to crystallisation, when leucin crystallises out. It is ob- tained pure by recrystallisation from boiling alcohol (Drechsel). 10. Tyrosin. — (a.) Observe under the microscope its crystalline form, fine long silky needles generally occur in sheaf-like bundles (fig. 5). It is insoluble in alcohol and in 1000 parts of cold water. (b.) Boil a hot watery solution with Millon's reagent (avoid excess) = a red colour (Hoffman's test). (c.) Dissolve a little tyrosin in a small quantity of concentrated sulphuric acid, and heat it for some time in boiling water, whereby tyrosin -sulphuric acid is formed. Neutralise the solution with barium carbonate and filter. The filtrate on being treated with neutral ferric chloride = a violet colour. 11. Leucin. — (a.) Under the microscope observe it in the form of brown balls, with radiating and concentric lines if it is impure ; and, when it is pure, as white shining lamellae, with a fatty glance. They are soluble in 27 parts of cold water, and much less soluble in alcohol. (b.) Heated in a tube it sublimes unchanged in very fine clouds with the odour of amylamine. A part is decomposed into C02 and CoH13N (amylamine). Many other substances, both nitrogenous and fatty, are de- rived from the metabolism of proteids and their allies in the economy. Fig. 5.— Crystals and Sheaves of Tyrosin. LESSON III. THE CARBOHYDRATES. The term Carbohydrate, first used by C. Schmidt, is applied to a large and important group of substances, which occur especi- ally 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, but to a much smaller extent, in animals, in which they are chiefly 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 O in the same proportion Ill] THE CARBOHYDRATES. \J as in water, i.e., 2 atoms of H to 1 atom of 0. As this propor- tion obtains in many other substances which certainly do not belong to the carbohydrate group, e.g., acetic acid (C2H400), lactic acid (C3H603), 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 carbo- hydrates contain multiples of this. To every 6 atoms of C there are at least 5 atoms of O, so that on the one hand acetic acid is excluded, and pyrogallic acid (CGHfi03) on the other. They have certain general characters. They are indifferent bodies, with a neutral reaction, which form only loose combina- tions with other 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 alkalies. (b.) They rotate the plane of polarised light. (c.) In contact with yeast they split up into alcohol and carbon dioxide, i.e., undergo fermentation. (Some do not undergo fer- mentation.) (d.) On heating with HC1 or H2S04 they are decomposed with the formation of lavulinic acid, humin substance, and formic acid. (e.) They give a deposit of yellow needles with phenyl-hydrazin. (/.) Various colour reactions with acids and aromatic alcohols. (g.) Some, e.g., cellulose and starch, are quite insoluble in water, while others are very sohdtle. Those which are very insoluble in water can usually be rendered soluble by heating them with an acid. This is a process of hydrolysis. They are less soluble 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. Inosit alone undergoes partial sublimation (Tollens). Classification of Carbohydrates : — I. Glucoses or II. Saccharoses or III. Amyloses or Monosaccharides, Disaccharides, Polysaccharides, CeH^Oe. C^H^On. «(C6H10O5). Grape-Sugar or Cane-Sugar. Starch. Dextrose. Lactose or Dextrin. Lrevulose. Sugar of Milk. Glycogen. Invert Sugar. Maltose. Granulose. Cellulose. B i8 PRACTICAL PHYSIOLOGY. [III. Inosit was formerly classified with the glucoses, but recent observers, e.g., Tollens, do not regard it as belonging to this sub- division. The saccharoses are converted into glucoses on boiling with dilute sulphuric acid. O j CglSos + H2° = 2C6Hi2°6 1. I. Starch (C6H10O5)n. — The n in this case is not less than 4, and may be 10 or 20; indeed, Brown and Heron suggest the formula io(C19H20O10). Starch 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 C02 in the leaves of the plant, or (b.) as reserve material in the roots, seeds, or shoots for the later periods of generation or vegetation. Preparation. — Wash a potato thoroughly, 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 off the supernatant fluid. (a.) Microscopical Examination. — Examine the white deposit of starch, noting that each starch-granule shows an eccentric Fig. 6.— Potato Starch. hilum with concentric markings. Add a very dilute solution of iodine. Each granule becomes blue, while the concentric mark- ings become more distinct. (b.) At this stage it is advantageous to compare the micro- scopic characters of other varieties of starch — e.g., rice, arrow- root, &c. (fig. 6). Each granule consists of an outer layer of cellulose enclosing alternating layers of granulose and cellulose, so that they present a laminated appearance. There are very great varieties in the shape and size of starch grains. Ill] THE CARBOHYDRATES. 1 9 (c.) Polariscope. — Examine starch granules with a polarisation microscope. With crossed Xicol's, when the field is dark, each granule shows 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. 7). (>l.) Squeeze some dry starch powder between the thumb and forefinger, and note the peculiar crepitation sound and feeling. 2. Prepare a Solution. — Place 1 gram of starch in a mortar, rub it up with a little cold water, and then add 50 cc. of boiling water, and rub FlG —potato up the whole together until the starch is ap- starch Gran- parently dissolved and a somewhat opalescent polarised light fluid is obtained. The starch granules swell up, ^--thv crossed 1 t t 4 -11 i i • 1 >icols, x 300. burst, and disappear. Allow the solution to cool. [In reality, the starch is only imperfectly dissolved by hot water.] (a.) Add powdered dry starch to cold water. It is insoluble. Filter, and test the filtrate with iodine. It gives no blue colour. (b.) The above method shows that it is imperfectly dissolved in warm water. If more starch be used, a thick " starch paste," which sets on cooling, is obtained. (c.) To a portion of the above fluid add a solution of iodine1 = a blue colour, which disappears on heating 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. (d.) Render some of the starch solution alkaline by adding caustic soda solution. Add iodine solution. oSTo blue colour is obtained. (e.) Acidify (d.) with dilute sulphuric acid, then add iodine = blue colour is obtained. (/.) To another portion of the solution add a few drops of dilute cupric sulphate and caustic soda, and boil = no reaction (compare " Grape-sugar "). (g.) To another portion of the solution add Fehling's solution, and boil = no reaction. (h.) Add tannic acid = yellowish precipitate, which dissolves on heating. 3. Starch is a Colloid. — Place some strong starch solution in a dialyser or parchment tube, and the latter in distilled water. Allow it to stand for some time, and test the water for starch ; none will be found. 1 Solution of Iodine. — Dissolve 2 grams of potassic iodide in 100 cc. of water, add I grain of iodine, and shake well. 20 PRACTICAL PHYSIOLOGY. [III. 4. II. Dextrin (British Gum) (C6H10O5). Prepare a Solution. — Dissolve some dextrin in boiling water, and observe that the solution is not opalescent. (a.) This proves its solubility in water. (p.) To a portion of the solution add a solution of iodine = reddish-brown colour, which disappears on heating and returns on cooling. [The student ought to use two test-tubes, placing the dextrin solution in one, and an equal volume of water in the other. Add to both an equal volume of solution of iodine, and thus compare the difference in colour.] (c.) Precipitate some from its solution by adding alcohol. (d.) Render 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). (/.) It is precipitated by ammonia and basic acetate of lead. There are several varieties of dextrin : — Erythro-dextrin gives a red colour with iodine solution. Achroodextrin gives no colour with iodine solution (see "Saliva"). 5. To Prepare Dextrin from Starch. — Make io grams of starch into a paste with 20 cc. of water, add to it 30 cc. of a 20 per cent, solution of sulphuric acid. Mix, and heat the mixture in a water-bath at 900 C. Cool and precipitate the dextrin by alcohol. Collect the white deposit, wash it with alcohol, and dry it. 6. III. Cellulose (C6Hi0O5)n occurs in every tissue of the higher plants, where it forms the walls of cells, and the great mass of the hard parts of wood. Cotton-wool may be used to test its reactions. (a.) It is insoluble in water and all the feebler solvents. (6.) It is soluble in Schweitzer's reagent, or a solution of ammonio-cupric oxide. This is prepared by dissolving slips of copper in ammonia in an open flask, or by dissolving precipitated hydrated oxide of copper in 20 per cent, ammonia. The former is prepared by precipitating a solution of sulphate of copper by soda in the presence of ammonium chloride. (c.) It is soluble in concentrated acids, and a gelatinous precipitate — called amyloid — falls on the addition of water. The substance precipitated gives a blue colour with iodine. It is also soluble in zinc chloride. (d.) It gives a blue colour with sulphuric acid and iodine, but not with the latter alone. 7. IV. Glycogen or Animal Starch, ^(C0H10O5). — Prepare a solution (see " Liver "). (a.) Take a portion of the solution ; note its opalescence ; add solution of iodine — - 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 difference in colour. The colour disappears on heating and reappears on cooling. It also dis- HI.] THE CARBOHYDRATES. 21 appears on the addition of alkalies, which break up the feeble compound. (b.) Add caustic soda and cupric sulphate solution = a blue solution, boil = no reduction. (c.) Add basic lead acetate = a precipitate (unlike dextrin). (d.) Add ammonia and basic lead acetate = a precipitate. (e.) Boil some with dilute hydrochloric acid. A reducing sugar is formed. Neutralise the acid with dilute caustic soda, and test with Febling's solution for a reducing sugar, maltose or dextrose, = a yellow precipitate. The solution so heated yields first dextrin and then sugar. (/.) Heated with potash or acetic acid the opalescence dimin- ishes, and the solution becomes clear. (g.) The solution is precipitated by alcohol (2 parts absolute alcohol to 1 part of the solution). (h.) Its solutions (even '6 per cent.) are powerfully dextro- rotatory (a)D =211° (Kiiiz). 8. V. Glucose, Dextrose, or Grape- Sugar (C6H12Or(). — In com- merce it occurs in warty uncrystallised masses of a yellowish or yellowish-brown colour. It is readily soluble in water. Prepare a solution by dissolving a small quantity in water. (a.) To the solution add iodine = no reaction. (b.) Taste the glucose, and note that it is not so sweet as cane- sugar. (c.) Heat the solution with sulphuric acid = darkens slowly. (d.) Dissolve some in boiling absolute alcohol. It crystallises in white needles when the alcohol cools. As to the tests, they have been classified as follows : — (A.) Yellow Colouration with Caustic Soda or Potash. (e.) Moore's Test. — Heat the solution with half its volume of caustic soda = a yellow or brown colour. The non-appearance of a yellow colour indicates the absence of dextrose, but the follow- ing substances give the same yellow colour with XaHO : — All the glucoses, together with milk-sugar and lactose. (B.) Tests Depending on Reduction. (/.) Trommer's Test. — To the solution add a drop or two of a solution of cupric sulphate (10 per cent.), and afterwards add caustic soda (or potash) 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 by all the glucoses). Heat slowly ; if grape-sugar be present the blue colour disappears, and a yellow or red precipitate of hydrated cuprous oxide is obtained. It is well to boil the surface of the fluid, and when the yellow pre- cipitate occurs, it contrasts sharply with the deep blue-coloured 22 PRACTICAL PHYSIOLOGY. [III. stratum below. The precipitate is first yellow, then yellowish- red, and finally red. It is better seen in reflected than trans- mitted light. It soon forms a precipitate at the bottom of the tube, where it is easily seen. If no sugar be present, only a black colour may be obtained. (g.) To the fluid add Fehling's solution; boil = a yellow or yellowish-red precipitate of hydrated cuprous oxide. [For the precautions to be observed in using Fehling's solution, and for some other tests for glucose, see "Urine."] (h.) Barford's Solution. — To 200 cc. of a solution of neutral acetate of copper, containing 1 part of the salt to 15 of water, add 5 cc. of a 38 per cent, solution of acetic acid. When heated with 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 this substance has been used to distinguish dextrose from maltose. (i.) Bottger's Bismuth Test. — Heat the fluid with caustic soda and a small quantity of dry basic bismuth nitrate = a grey or black reduction product of bismuth oxide. For Nylander's modi- fication, see "Urine." In all reactions depending on reduction, one must recollect that some substances which are by no means related to the glucoses — e.g., uric acid, kreatinin, phenyl-hydrazin — may cause reduction, and thus lead one into error. (0.) Other Reactions. (j.) Phenyl - Hydrazin Test. — Two parts of phenyl-hydrazin hydrochloride and three of acetate of soda are mixed in a test-tube with 6-10 cc. of the sugar solution. Place the tube for 20-30 minutes in boiling water, and then place the tube in cold water. If sugar be present, a yellow crys- talline deposit is formed, which, when examined /^^K^^^ by the microscope, is seen to consist of yellow ™'' needles either detached or arranged in rosettes SenyiTaSosazo^ (%• 8)* Tne substance formed is phenyl-glu- cosazon with a melting-point of 204°. This is an extremely important and reliable reaction. The best proportions for the ingredients are 1 part dextrose, 2 hydro- chloride of phenyl-hydrazin, 3 sodic acetate, and 20 water. The substance formed is but slightly soluble in water. According to E. Fischer, the following is the reaction which takes place : — C6H1206 + 2C6H5N2H3 = C18H22N404 + 2H20 + 2H. Phenyl-glucosazon. (k.) Molisch's Test. — (i.) To the solution add a drop or two of a 15-20 per cent, alcoholic solution of a-naphthol, and 1-2 vols, of m.] THE CARBOHYDRATES. 23 concentrated sulphuric acid. The colour which first appears is violet; water causes a bluish-violet deposit, (ii.) If, instead of the naphthol, an alcoholic solution of thymol be used, a red colour is obtained. Seegen, however, points out that this re- action can be obtained by other substances, e.g., albumin, which, however, is denied by Alolisch. 9. To Prepare Glucose. — Boil some starch solution for some time (until the fluid becomes clear) with a few drops of 20 per cent, sulphuric acid. After neutralising, test the fluid for glucose by the tests (b.) or (c). A large number of intermediate products, however, are formed. They are as follows (see also " Saliva ") : — Starch ) jy. ... . ,. Soluble starch (amidulin or amylodextrin) . \ v iiriGtiGS ) , I Erythrodextrin .... Iodine gives violet and red. -p. . i Achroodextrin .... No reaction with iodine. TVTnif^o \ Fehling's solution reduced. ( Barford s not. Dextrose Both are reduced. 10. VI. Maltose (C12H.72011). — It forms a fine white warty mass of needles. (a.) Take 1 gram of ground malt, mix it with ten times the quantity of water, place the mixture in a beaker, and keep it at 60 ° C. for half an hour. Then boil and filter ; the filtrate con- tains maltose and dextrin. (b.) Test for a reducing sugar with Fehling's solution or other suitable test. (See also " Salivary digestion.") (c.) With Barford's reagent, i.e., when boiled with half its volume of copper acetate, acidulated with acetic acid = no re- duction. In this respect, and in some others, it differs from dextrose. (d.) It is soluble in water and alcohol. Its specific rotatory power is 138.30, i.e., it is greater than that of dextrose, but its reducing power (on Fehling's solution) is only two-thirds of that of dextrose. (e.) Boiled for i\ hours with the phenyl-hydrazin test it yields phenyl-maltosazon. 11. Preparation of Maltose. — Take 1 part of potato-starch and make it into a paste with 10 of water. Digest the paste with a filtered extract of low-dried malt (200 grams to 1 litre of water) for an hour at 57-60° C, filter, evaporate, precipitate the dextrin with alcohol, concentrate the filtrate to a syrup, and allow the maltose to crystallise. 12. VII. Lactose (Milk-Sugar), C12H.>oOn + H,0 (see " Milk "). — It undergoes the lactic acid fermentation. 24 PRACTICAL PHYSIOLOGY. [III. (a.) Observe its crystalline form, its whiteness and hardness. It is not so sweet as cane-sugar. (b.) It is less soluble in water than cane- or grape-sugar, and insoluble in alcohol. (c.) Heat its solution carefully with sulphuric acid = chars slowly. (d.) Add one drop of solution of cupric sulphate and excess of caustic soda and heat = yellow or red precipitate (like dextrose). (e.) It is precipitated from its saturated watery solution by absolute alcohol. 13. Preparation of Lactose (C12H22O11 + H20). — Boil the filtrate from Lesson I. 7, III. (2), filter, evaporate it with magnesic carbonate, exhaust the residue with alcohol, and extract the residue insoluble in alcohol with boiling water. The watery extract is mixed, filtered, evaporated to a syrup, and allowed to stand in the cold, when milk-sugar separates. Milk-sugar is readily soluble in water, but not in alcohol. Heated with nitric acid, it yields mucic acid, which separates as a white insoluble powder (distinguishing it from cane-sugar, dextrose, and maltose). 14. VIII. Cane-Sugar (CJS^On). (a.) Observe its crystalline form and sweet taste. (b.) Its solutions do not reduce Fehling's solutions (many of the commercial sugars, however, contain sufficient reducing sugar to do this). (c.) Add a drop of solution of cupric sulphate and excess of caustic soda, and heat. With a pure sugar there should be no reduction. (d.) Place some cane-sugar in a beaker, pour strong sulphuric acid on it, and add a few drops of water ; very quickly the whole mass is charred. (e.) Heat the solution with caustic soda = it darkens slowly. (/.) It is practically insoluble in absolute alcohol, but its solu- bility greatly increases with the dilution of the alcohol. (a.) 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," and the solution contains a mixture of dextrose and lsevulose. Test its reducing power with Fehling's solution. Cane-Sugar. Water. Glucose. Lsevulose. C12H22On + H20 = C6H1206 + C6H1206. 15. Invert Sugar — a mixture of grape-sugar and fruit-sugar — is widely distributed throughout the vegetable kingdom, and is so called because it rotates the plane of polarised light to the left, the specific rotatory power of the lsevulose being greater than that of dextrose at ordinary temperatures. III.] THE CARBOHYDRATES. 25 16. Conversion of Starch into a Reducing 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. (b.) Test it with iodine = a blue colour, showing that some soluble starch (amidulin) still remains unconverted into a reduc- ing sugar. ADDITIONAL EXERCISES. POLARIMETERS. 17. Circumpolarisation. — Certain substances when dissolved possess the power of rotating the plane of polarised light, e.g., the proteids, sugars, &c. The extent of the rotation depends on the amount of the active substance in solution. The direction of rotation — i.e., to the right or the left — is constant for each active substance. Of course, light of the same wave-length must be used. The light obtained from the volatilisation of common salt 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 plane of polarised light which is produced by I gram of the substance dissolved in I cc. of liquid, when examined in a layer I decimetre thick. Those substances which cause specific rotation are spoken of as "optically active; " those which do not, as "inactive." If a — the observed rotation ; p — the weight in grams of the active substances contained in 1 cc. of liquid ; I = the length of the tube in decimetres ; (a)D = the specific rotation for light corresponding to the light of a sodium flame ; then («)d=±^ pi The sign -f or — indicates that the substance is dextro- or lsevo-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. 18. Determination of the Specific Rotatory Power of Dextrose. (a.) Fill one of the decimetre tubes with distilled water, taking care that 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 that it lies in the course of the rays of polarised light. (b.) Place some common salt (or fused common sait and sodic 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 26 PRACTICAL PHYSIOLOGY. [III. suitable holder, so that the salt is volatilised in the outer part of the flame. In the newer form of the instrument supplied by Laurent, there are two Bunsen-burners, placed the one behind the other, which give very much more light. Every part of the apparatus must be scrupulously clean. (c.) Bring the zero of the vernier to coincide with 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 Fig. 9.— Laurent's Half-Shadow Polarimeter. 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 the 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 perfectly clear solution 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. Ill] THE CARBOHYDRATES. 27 (e.) Repeat the process several times, and take the mean of the readings. The difference between this reading and the first at (a), when the tube was filled with distilled water — i.e., zero — is the rotation due to the dextrose = a. (/.) Place 10 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 10 cc. ; so that the amount in I cc. is got at once =p. (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 Fig. 10.— Wild's rolaristrobometer. IOO 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 11. 6°. (a)D = n.6° .11x2 53c 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 : — 28 PRACTICAL PHYSIOLOGY. [III. Proteids. — Egg- albumin — 35.5°; serum-albumin — 560: syn- tonin — 72°; alkali-albumin prepared from serum-albumin — 86°, when prepared from egg-albumin — 470. Carbohydrates. — Glucose + 560; maltose + 1500; lactose + 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 loevulose, when heated from 20-900 C, falls in the proportion of 3:2. It is best, therefore, to work at a constant temperature, say 200 C. Again, some solutions have not the same S.R. when they are first dissolved 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 Polaristrobometer. — Between the polariser (which can be rotated) and analyser of this instrument is placed a Savart's polariscope, which 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-flame enters at D, traverses a Nicol's prism which is fixed to and moves with the graduated index K. The polarised 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 inter- ference-lines, which are viewed by means of a lens of short focus. Between M and N is a diaphragm with X-shaped crossed lines. Beyond M, which is designed to protect the eye 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 off the scale, there is a telescope B. In S is a small mirror which reflects the flame of a movable source of light upon the nonius. Usually the instrument is made for a column of fluid 220 mm. long. (1.) Light the movable gas-flame opposite Q. Esti- mate 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 Piq zl —a Interference traversed by dark interference-lines (fig. 11, a). On lines seen with fig. 10. 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. 1 1, b. (2.) Replace the empty tube with the fluid to be investigated, when the interference-lines reappear. Suppose the substance is dextro-laevatory, then rotate the Nicol 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. IV.] FATS — BONE. 29 LESSON IV. FATS-BONE-EXERCISES ON THE FOREGOING. NEUTRAL FATS. The neutral fats of the body generally consist of a mixture 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 jU3> 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. 1. Reactions. (a.) They are lighter than water; sp. gr. .91-94. (b.) Use almond or olive oil or lard, and observe that fat is soluble in ether, chloroform, and hot alcohol, but insoluble in water. (c.) Dissolve a little fat in 3 cc. ether. Let a drop of the ethereal solution fall on paper, e.g., a cigarette paper = a greasy stain on the paper, and the stain does not disappear with strong heat. (d.) To olive-oil or suet add caustic potash or soda, and boil = saponification. 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. Tri- Stearin. Potash. Potassic Stearate. Glycerin. 3(C18H350 ) \ Kl0. .01SH350 [ C3H3 ) C3 H5 ) u3 + 3H j u - 3 K J u H3 j U3 This is the process of saponification. (e.) Heat some lard and caustic soda solution in a capsule to form a soap ; decompose the latter by heating it with dilute sulphuric acid, and observe the liberated fatty acids floating on the top. 30 PEACTICAL PHYSIOLOGY. [IV. (/.) Proceed as in (d.), and add to the soap solution crystals of sodic chloride until the soaps separate. (y.) 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 micro- scopically, 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. (A.) Gad's Emulsion Experiment. — Place in a watch-glass a solution of sodic carbonate (.25 per cent.), and on the latter place a drop of rancid oil. The drop comes to rest, but soon the oil-drop shows a white rim, and at the same time a white milk opacity ex- tends over the soda solution. Examined under the microscope, note the lively movement in the neighbourhood of the fat-droplet, due to the separation of ex- cessively minute particles of oil from the drop of oil. The particles are very minute and regular ; the white fluid is a fine and uniform emulsion (fig. 12). This experiment has an important bearing on the formation of emulsion in the intestine in connection with the pancreatic diges- tion of fats. (i ) Shake up olive-oil with a solution of albumin in a test-tube „ „• . = an emulsion. Examine it micro- FlG. 12. — Gad s Experiment. . ,, scopically. (/.) 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.) To Decalcify Bone. — Place a small thin dry bone in dilute hydrochloric acid (1:8) for a few days. Its mineral matter will be gradually dissolved out, when the bone, although retaining its original form, loses its rigidity, and becomes pliable, elastic, and so soft as to be capable of being cut with a knife. What remains is the organic matrix or ossein. Keep the solution obtained. (b.) Wash the decalcified bone thoroughly with water, in which it is insoluble. Boil it for a long time, and from it gelatin will be obtained. Test the solution for gelatin (Lesson II. 1). (c.) Decalcify a small portion of a dry bone with picric acid. IV.] FATS — BONE. 3 I (B.) Mineral Matter in Bone. (a.) Examine a piece of bone which has been incinerated in a clear fire. At first the bone becomes black from the carbon of its organic matter, but ultimately it becomes white. What re- mains 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 (C02) are given off, indicating the presence of a carbonate ; dilute the solution, add excess of ammonia = a white precipitate of phosphate of lime and phos- phate of magnesia. (c.) 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. (d.) 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. 3. Method of Analysing (Qualitatively) a Fluid containing Phosphates, the more common Proteids, and Carbohydrates. (A.) Note the following physical characters : — 1. Transparency. — If the solution be opaque, examine it with the microscope. Filter, and examine the residue, if any, as a solid. 2. Colour. — In some fluids the colour may suggest the presence of particular bodies, e.g., blood or bile. 3. Smell. 4. Taste. 5. Specific Gravity. (See " Urine.") 6. Boil. — Does the fluid become clear, or is a deposit formed ] The latter suggests certain proteids. Is any odour evolved ? 7. Any Solid Residue. — Evaporate some to dryness. Xote the characters of the residue, if any, and whether the residue chars or has any special odour. 8. Reaction. (B.) Test for Proteids. (a.) If the reaction be acid or alkaline, neutralise with verv dilute sodic carbonate or XaOH, or hydrochloric acid, if necessary. A precipitate = a derived albumin (alkali- or acid-albumin) or phosphates. Filter, wash the precipitate, and if the latter gives the xanthoproteic reaction, it is acid- or alkali-albumin. If not, it is earthy phosphates. Analyse the filtrate as follows : — (C.) If the fluid be neutral to begin with, or if the filtrate from (B.) be used — (a.) Acidulate with a few drops of dilute acetic acid. Boil. 32 PRACTICAL PHYSIOLOGY. [IV. Coagulation may be due to albumins or globulins. Keep the nitrate obtained after boiling. Test the coagulum for proteid (xanthoproteic test, &c), and the fluid as well. (b.) Saturate part of the original solution with crystals of MgS04. A precipitate = globulin. Filter, the filtrate may still contain albumin, boil it = coagulum = native albumins. Distin- guish between egg- and serum-albumin. (c.) See if the original solution is precipitated by neutral ammonium sulphate. Test the precipitate for hemi-albumose. Try the hemi-albumose tests with the original solution. (d.) Test if the filtrate from [a.) contains peptones by the biuret test and Millon's reagent. (e.) Acidulate and boil the filtrate from (B.) to remove albumins, precipitate any albumoses by ammonium sulphate, and the pep- tones from this filtrate by alcohol. The final filtrate, or the original solution, provided there be no proteids present, is treated as follows : — (D.) (a.) Try the general proteid tests. (b.) A solution giving only the xanthoproteic and Millon's reaction may contain mucin or chondrin. (c.) If the xanthoproteic, Millon's, and the biuret tests succeed, but there is no precipitate with acetic acid and ferrocyanide of potassium, gelatin is present. (d.) If it gives Millon's reaction alone, suspect tyrosin. Eva- porate to dryness. Extract the residue with hot dilute ammonia, evaporate, and search for microscopic crystals. (E. ) Test for Carbohydrates. (a.) If neither phosphates nor proteids have been found, use the original solution ; but if proteids are present, remove them by boiling with acetic acid and sodic sulphate (the peptones, however, if present, still remain in solution). Filter, and use the filtrate for testing. (b.) Add iodine after acidulation if necessary, a blue colour = starch ; a port-wine colour = dextrin or glycogen. Confirm by other tests. (c.) Test for sugar if no peptones are present. If peptones are present, evaporate to dryness, extract the residue in 98 per cent, alcohol, filter. Evaporate the alcohol, redissolve the residue in water, and test for sugar. (d.) Test also for non-reducing sugars by boiling with dilute sulphuric acid, when a non-reducing sugar is converted into a reducing one. Should the solution contain urea, uric acid, ferments, &c, other methods must be used. These will be referred to more fully after the bodies have been more exhaustively considered. V.] THE BLOOD. 33 (F.) Test for Urea. (a.) Add the baryta mixture (see "Urine") to precipitate the sulphates and phosphates. Filter, and test the filtrate for chlorides. (b.) To the solution add mercuric nitrate = white precipitate, suspect urea. If chlorides be found, an excess of mercuric nitrate must be added ; but if no chlorides are present, the white curdy precipitate falls at once. (c.) Concentrate a portion to dryness, and extract the residue with absolute alcohol. Examine a drop on a slide, after evapora- tion, for crystals of urea. (d.) A portion evaporated nearly to dryness and treated with ■pure nitric acid = crystals of urea nitrate. (G.) Test for Uric Acid. (a.) Evaporate to dryness and use the murexide test. (See " Urine " for other tests.) 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 needle prick the skin just at the root of the nail. The blood will flow freely. Bring a strip of dry, smooth, glazed, neutral litmus paper in contact with the blood. Allow the blood to remain on it for a short time ; then wash it off with a stream of distilled water from a wash-bottle, when a blue spot upon a red or violet ground will be seen, indicating its alkaline reaction. 2. Blcod is Opaque. (a.) Place a thin layer of defibrinated blood on a microscopic slide, and try to read some printed matter through it. This will be found impracticable. 3. To make Blood Transparent or Laky. — Place 10 cc. of the defibrinated blood provided for you in three test-tubes, labelling them A, B, and C. Keep A for comparison. (a.) To B add 5 volumes of water, and warm slightly, noting the change of colour by reflected and transmitted light. When looked at by reflected light, it is much darker in colour — in fact, it looks almost black — but by transmitted light it is transparent. Test this by looking as in 2 (a.) at printed matter. (b.) To C add an aqueous solution of taurocholate of soda. c 34 PRACTICAL PHYSIOLOGY. [V. Test its transparency as above. In 2, the haemoglobin is still within the blood corpuscles. In the others — 3 (a.), (b.) — it is dissolved out, and in solution. 4. Specific Gravity of Blood. — Make a number of solutions of sulphate of soda, varying in sp. gr. from 1.050- 1. 075. At least twenty separate solutions are required, each with a definite sp. 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 caoutchouc cap. A drop of blood is obtained from a finger, and by pressing lightly on the caoutchouc cap a quantity of the freshly-shed blood is drawn up into the capillar}' part of the tube. The tip of the fine capillary tube is at once immersed in one of the solutions of sodic sulphate and a drop of the blood expressed into the saline solution, and it is noted whether it sinks or floats. 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. 5. Action of a Saline Solution. (a.) Take 2 cc. of defibrinated blood in a test-tube, label it D, add 5 volumes of a 10 per cent, solution of sodic chloride. Observe the change of colour. 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 volumes of a dilute solution of NaCl (.5-2 per cent.). The red corpuscles subside, and the supernatant fluid can be poured off. Wash the corpuscles several times in this way. They will be required for the preparation of haemoglobin (p. 63). 7. Haemoglobin does not Dialyse. (a.) Place a watery solution of defibrinated blood in a dialyser (a bulb form or a parchment tube), and suspend it in a large vessel of distilled water. Carefully test the dialyser beforehand to see 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. (b.) After several hours observe that no haemoglobin has passed into the water. (c.) Test the diffusate for chlorides. 8. Phenomena of Coagulation. — Place a small porcelain cap- sule on the table; decapitate a rat, and allow the blood to flow into the capsule. Within a few minutes the blood congeals, and when the vessel is tilted the blood no longer flows as a fluid, but as a solid. It then coagulates completely. 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. V.] THE BLOOD. 35 9. Formation of Clot and Serum. — This is readily done on a small scale in a capillary tube with a small bulb at its middle. Prick a finger, or squeeze the blood from the heart of a pithed frog. Draw out a glass tube into a fine capillary pipette at both ends, leaving a bulb in the middle, and suck some uncoagulated blood into it, seal up the ends of the tube, allow the blood to coagulate, and examine the tube under a microscope. Observe the small red shrunken clot, and the serum squeezed out of the latter. 10. Frog's Biood— Coagulation of the Plasma.— Place 5 cc. of normal saline (0.75 per cent, salt solution) in a small test-tube surrounded with ice. Expose the heart of a pithed frog, and cut into the ventricle, allowing the blood as it escapes to fluvv into the normal saline. Mix the two, and the corpuscles (owing to their greater specific 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 blood obtained from the slaiigbter-house. Collect the blood of a sheep or ox in a wide cylindrical vessel, and allow it to coagulate. 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 obtained, study it, noting that the upper layer of the clot is paler in colour ; this is the buffy coat. 12. Circumstancss Influencing Coagulation. Effect of Cold. — Place a small platinum 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 con- geals, but it is not coagulated. As soon as the blood becomes solid, remove the thimble and thaw the blood by placing it on the warm palm of the hand, when the blood becomes fluid, so that it can be poured into a watch-glass j if the vessel be once more placed 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 altered. The blood becomes darker in colour and trans- parent. This is the laky condition due to the dispharga of the haemoglobin from the corpuscles. Place the vessel with the fluid blood on the table, and it clots or forms a firm jelly. 13. Influence of Neutral Salts on Coagulation. — Take to the slaughter-house a vessel capable of holding 500 cc, but previously place in it 170 cc. of a saturated solution of sodic sulphate or magnesic sulphate. Allow enough blood from an animal to run into the saline solution to lill the vessel, and mix them thoroughly. 36 PRACTICAL PHYSIOLOGY. [V. The blood does not clot, but remains fluid. Place the vessel aside on ice, and note that the corpuscles subside, leaving a clear yellowish layer on the surface — the plasma mixed with the saline solution, and known as salted plasma. (a.) Pipette off the salted plasma — use 2 cg. — add to it 3 to 5 volumes of water, and observe that it clots after a time. The clotting is hastened by the action of gentle heat. In laboratories where a centrifugal apparatus is in use, the corpuscles can be rapidly separated from the plasma, and enough of the latter obtained for the requirements of a large number of students. (6.) Place 15 cc. of the salted plasma — separated by means of the centrifugal apparatus — in a tall, narrow, cylindrical, stoppered glass tube. Add powdered sodic chloride, and shake the whole vigorously, when a white flocculent precipitate is thrown down. Allow the precipitate to subside. Decant the 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 was not dissolved in water until many hours after it was deposited. 14. Defibrinated Blood. — In a slaughter-house allow the blood from an animal 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, and although set aside for any length of time, it does not coagulate spontaneously. («.) With a few thin twigs, or the barbed end of a quill, beat some freshly- shed blood, and observe the fibrin sticking to the twigs. Wash it. 15. I. Fibrin. — Take the twigs coated with fibrin of the pre- vious experiment. Wash away the colouring-matter with a stream of water until the fibrin becomes quite white. (a.) Study its physical properties : it is a white, fibrous, highly elastic substance. Stretch some fibres to observe their extensi- bility ; on freeing them, they regain their shape, showing their elasticity. (b.) Place a few fibrils in absolute alcohol to rob them of water. They become brittle and lose their elasticity. V.] THE BLOOD. 37 (c.) Place a small quantity of fibrin in a test-tube with some o. 2 per cent, hydrochloric acid in the cold. It swells up and becomes clear and transparent, but does not dissolve. (d.) Repeat (c), 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, III. 3). ( -Method i>f Incinerating Obtain the Ash. a Deposit to PRACTICAL PHYSIOLOGY. [VI. LESSON VI. THE COLOURED BLOOD-CORPUSCLES. SPECTRA OF HEMOGLOBIN AND ITS COMPOUNDS. Enumeration of the Corpuscles. — Several forms of instruments are in use, e.g., those of Malassez, Zeiss, Bizzozero, and Gowers. 1. The Hsemocytometer of Gowers (fig. 16) can be used with any microscope, and consists of — (a.) A small pipette, which, when filled to the mark on its stem, holds 995 c.mm. (fig. 16, A). FIG. 16. — Gowers' Hsemocytometer. A. Pipette for measuring the diluting solution ; B. For measuring the blood ; C. Cell with divisions on the floor, mounted on a slide, to which springs are fixed to secure the cover-glass ; D. Vessel in which the solution is made ; E. Spud for mixing the blood and solution ; F. Guarded spear-pointed needle. (b.) A capillary tube to hold 5 c.mm. (B). (c.) A small glass jar in which the blood is diluted (D). (d.) A glass stirring rod (E). VI] THE COLOURED BLOOD-CORPUSCLES. 43 (, and a second half-way between D and E. (c.) To some of the hsematin solution (in strong sulphuric acid), add a large excess of water, which throws down part of the hsematoporphyrin in the form of a brown precipitate, which is more copious if the acid be neutralised with an alkali, e.g., caustic soda. Dissolve some of the brown deposit in caustic soda, and examine it spectroscopically. (d.) The spectrum shows four absorption-bands; a faint band midway between 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. Spectrum of Picro-Carmine. — Observe the spectrum of this fluid. It gives none of the characteristic reactions for blood, either by the spectrum or other tests, e.g., for proteids. VII.] WAVE-LENGTHS. 53 LESSON VII. WAVE-LENGTHS-DERIVATIVES OF HEMO- GLOBIN-ESTIMATION OP HEMOGLOBIN. Spectroscopic Determination of Wave-Lengths. — Use Zeiss's spectroscope, which is provided with an illuminated scale for this purpose. 1. W.L. of Absorption-Bands of Oxy-Haemoglobin. (a.) Arrange the apparatus as shown in fig. 27. A is the telescope through which the observer looks and sees the spectrum FIG. 27. — Arrangement of the Spectroscope for Determining Wave-Lengths. A. Tele- scope ; B. Collimator tube ; C. Scale tube ; D. ILematiuometer. obtained by the light passing through B, and dispersed by the 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 haematinometer containing the dilute blood. (b.) Throw a piece of black velvet cloth over the prism ; light both lamps ; look through B ; adjust the slit in A and the tele- 54 PEACTICAL PHYSIOLOGY. [VII. scope in B, 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. In a loop of platinum wire burn some common salt in the flame to get the bright 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). A a b c Fig. 28.— The Spectra of Oxy-Hsemoglobin (1, 2, 3, 4), 1 = .01, 2 = 0.9, 3 = .37, 4 = .8 per cent, of Haemoglobin, Haemoglobin (5), and Carbonic Oxide Haemoglobin (6). Wave- lengths added. The numbers attached to the scale indicate wave-lengths expressed in ioo,oooths of a millimetre. Thus, Fraunhofer's line, D, which corresponds to division 58.9 of the scale, has a wave-length of 589 million ths of a millimetre. The wave-lengths of Fraunhofer's lines are: — A =760.4, B = 687.4, C = 656.7, D = 589.4, E = 527.3, F = 486.5. (c.) Using one of the blank maps provided for you (i.e., the maps supplied with Zeiss's spectroscope — 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 haemoglobin — r part in 1000 of water is best — and place it in the hsematinometer, D, which is placed in position between the flame and the spectro- VII.] WAVE-LENGTHS. 55 scope, as shown in fig. 27. The distance between the parallel faces of D is 1 cm. The spectrum shows the two absorption- bands of oxy-hsemoglobin between D and E. The narrower, sharper, and blacker band near D has its centre corresponding with the W.L. 579, and it may conveniently be expressed by the letter a of the oxy-hsemoglobin spectrum. The other absorption-band near E, and conveniently designated f3, is broader, not so dark, and has less sharply defined edges than a. Its centre corresponds to the W.L. 553.8. 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 with a stronger solution of blood, and observe how A a B C FIG. 29.— Spectra of some of the Derivatives of Haemoglobin. 1. Hrcmatin in alkaline solution ; 2. The same, but more concentrated ; 3. Hremochromogen ; 4. Methsemo- globin ; 5. Acid hrematin (acetic acid) ; 6. Acid hsematin in ethereal solution. 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-ha°mo- 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 56 PRACTICAL PHYSIOLOGY. [VIL Hb. This 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 D 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-haemo- globin of the same strength. On further dilution of the solu- tion, the band does not resolve itself into two bands, but simply diminishes in width and intensity (fig. 28, 5). 3. W.L. of the Spectrum of Carbonic Oxide Haemoglobin. (a.) Use a dilute solution of carbonic oxide haemoglobin of such a strength as to give the two characteristic absorption -bands. (/a) Observe the two bands, a and /3, like those of Hb02, but both are very slightly more towards the violet end of the spectrum, a extends from about W.L. 587 to 564, and f3 from 547 to 529. (c.) No reduction is obtained by reducing agents (fig. 28, 6). 4. Preparation of Haematin. (a.) Make defibrinated blood into a paste with potassic carbo- nate. Dry the paste on a water-bath. Place some of the paste in a flask, add 4 volumes of alcohol, and boil on a water-bath. Filter, and an alkaline brown solution of haematin 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 (a.) with dilute sulphuric acid, filter, and keep the filtrate. Observe the spectrum of acid haematin in the filtrate (figs. 24, 5, and 29, 5). (c.) Add excess of ammonia to the acid filtrate of (&.), and filter off the precipitate, keep the filtrate, and observe that it is dichroic. Observe the spectrum of alkali haematin in the filtrate (fig. 24, 6). (d.) Evaporate the filtrate from (c.) 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 1200 C. This is nearly pure haematin. (e.) It is convenient to keep in stock haematin prepared as follows : — Extract defibrinated blood or blood-clot (ox or sheep) with rectified spirit containing pure sulphuric acid (1 : 20). Filter; the solution gives the spectrum of acid haematin. Add an equal volume of water and then chloroform. The chloroform becomes brown, and there is a precipitate of proteids. Separate the chloroform extract, wash it with water to remove the acid. Separate the chloroform, and allow it to evaporate. The dark VII.] ESTIMATION OF HEMOGLOBIN. 57 brown residue is impure hsematin. When dissolved in alcohol and caustic soda it gives the spectrum of alkali hsematin, and on adding ammonium sulphide that of haemochromogen. If it is dissolved in H2S04, and filtered through asbestos, the red filtrate gives the spectrum of hsemato-porphyrin {M&cMunn). 5. Haemin Crystals. — Place some powdered dried blood on a glass slide, add a crystal of sodium chloride, and a few drops of (jlacial acetic acid. Cover with a cover - glass, and heat carefully over a flame until bubbles of gas are given off. After cooling, brown or black rhombic crystals of haematin are to be seen with a microscope (fig. 30). 6. Detection of Blood- Stains. — Use a piece of rag stained with blood. (a.) Moisten a part of the stain with glycerin, and after a time express the liquor, and observe it microscopically for blood- corpuscles. (b.) 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 spec- troscopically. (c.) Boil some of the extract with hydrochloric acid, and add potassic ferrocyanide ; a blue colour indicates the presence of iron. [d.) Use the stain for the haemin test, doing the test in a watch-glass. 7. The Haemoglobinometer of Gowers is used for the clinical estimation of haemoglobin (fig. 31). 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 ave- rage normal blood (one hundred times) is taken as the standard. The quantity of haemoglobin is indicated by the amount of dis- tilled water 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 cmm. of blood, in 2 cc. of water (1 in 100). The second tube (C) is graduated, ioo°= 2 cc. (100 times 20 cmm.). The 20 cmm. of blood are measured by a capillary pipette (B). (a.) Place a few drops of distilled water in the bottom of the graduated tube (C). 53 PBACTICAL PHYSIOLOGY. [VII. (&.) 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. (c.) 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 which has been added (i.e., the degree of dilu- tion) indicates the amount of haemoglobin. " Since average normal blood yields the tint of the standard at 100° of dilution, the number of degrees of dilution necessary to obtain the same tint with a given specimen of blood is the per- FlG. 31.— A. Pipette bottle for distilled water ; B. Capillary pipette ; C. Graduated tube ; D. Tube with standard dilution ; F. Lancet for pricking the finger. centage proportion of the haemoglobin 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 300 of dilution. Hence it contained only 30 per cent, of the normal quantity of haemoglobin. By ascertaining with the haemacytometer the cor- puscular richness of the blood, we are able to compare the two. A fraction, of which the numerator is the percentage of haemo- globin, and the denominator the percentage of corpuscles, gives at once the average value per corpuscle. Thus the blood men- tioned above containing 30 per cent, of haemoglobin contained 60 per cent, of corpuscles; hence the average value of each cor- puscle was |-£ or half of the normal. Variations in the amount of VIL] ESTIMATION OF HEMOGLOBIN. 59 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. In practice it will be found that, during 6 or 8 degrees of dilu- tion, it is difficult to distinguish a difference between the tint of the 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 Haemometer. — This apparatus (fig. 32) consists of a horse-shoe stand with a pillar bearing a reflecting 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 platform (M) is a small cylindrical vessel divided into Fig. 32.— Fleischl's Htemometer. two compartments (a and a') by a vertical septum. In one compartment is placed pure water, and in the other the blood to be investigated. A scale (P) on the slot of the instrument enables one to read off directly the percentage of haemoglobin. (a.) Fill with a pipette the compartment (a') over the wedge with distilled water, and see that the surface of the water is quite level with the top of the 6o PRACTICAL PHYSIOLOGY. [VII. cylinder. Fill the other compartment (a), that for the blood, about one- quarter with distilled water. (b.) Prick the finger as in 7 with the instrument supplied for the purpose. Fill the short automatic capillary pipette tube with blood. Its capacity is 6.5 c.mm. 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 pipette slightly greasy on the outer surface. (c.) Dissolve the blood obtained in (b.) in the water of the blood-compart- ment (a1), washing out every trace of blood from the pipette. Mix the blood and water thoroughly. Clean the pipette. Then fill the blood compartment exactly to the surface with distilled water, seeing that its surface also is per- fectly level. (d. ) Arrange a lamp 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 compartments is identical. Kead off the scale, which is so constructed as to give the percentage of haemoglobin. 9. Bizzozero's Chromo-Cytometer. — The chief part of the instrument con- sists of two tubes (fig. 33, 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 m G | 11 -C4- = CT the other, so that both glasses touch. Connected with the outer tube is a small open reservoir (r), from which fluid can pass into the variable space 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 hsematoscope, and the screw is so graduated as to indicate the distance between the two plates, 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. 33, cd) — that each subdivision of the index = — '-2 25 = O.02 mm. When the inner tube is screwed home and touches the glass disc in the outer tube, the index stands at o on the scale. If 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 thimbles with flat bottoms, containing 2 and 4 cc. respectively ; a pipette graduated to hold -J and I cc, and another pipette for 10 and 20 cmm., 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 (S. Lea, Journal of Physiology, v. 239). FiG. 33-— General View of the Chromo-Cytometer. ab and cd. Two tubes, the one fits inside the other ; r. Reservoir communicating with the space between c and b when cd is screwed into ab ; cr. Milled-head and index scale to the left of it, for the tinted glass ; m. Handle. VII.] ESTIMATION OF HAEMOGLOBIN". 6l Fig. 34.— Showing how cd fits into ab. zz'. Plates of glass closing the ends of ab and cd; other letters as in fig- 33- Method of Using the Instrument as a Cytometer. — r. By means of the pipette place 5 ec. of normal saline solution in a glass thimble. 2. With a lancette or needle puncture the skin of the finger at the edge of the nail. 3. With the pipette suck up exactly 10 cmm. of blood. Mix this blood with the .5 ccm. saline solu- tion, and suck part of the latter several times into the capillary tube, so as to remove every trace of blood TQ P ~^— ^ from the pipette. Mix the fluids thoroughly. Care- fully cleanse the pipette with water. 4. Pour the mixture into the reservoir (r) 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 1^ metres, and, taking the instrument in the left hand, bring the open end of the tubes to the right eye. W-.th 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 occurs. Read off on the scale the thickness of the stratum of fluid. Graduation of the Instrument as a Ci/tnmeter. — In this instrument the graduation is obtained from the thickness of the layer of blood itself, and the amount of haemoglobin 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 appears that in healthy blood the out- lines of the flame of a candle are distinctly seen through a layer of the mixture of blood mm. in thickness. 100 Let the number no correspond to I, or to 100 parts of haemoglobin ; then it is easy to calculate the relative value of the subdivisions of the scale on the tube of the instrument. Let g — the degree of the scale for normal blood ; g', that for the blood being investigated ; e, amount of haemoglobin in the former ; and e', the amount sought for in the latter. Assuming that the product of the quantity of haemoglobin and the thickness of the stratum of blood is constant, so that Then we have eg = e g e' = c g 9*. Let us assume that the blood investigated gave the number 1S0; then, using the above data, we have : — e' = 100. 1 10 l8o~ 11,000 1 So 61. 1. 62 PRACTICAL PHYSIOLOGY. [VII. Haemoglobin. Cytometer Scale. Haemoglobin . IOO.O 170 • 64.7 91.6 180 . 61. 1 . 84.6 190 ■ 57-9 • ySA 200 • 550 73-3 2IO • 52-4 . 6^.7 220 • 50.° The blood, therefore, contains 61. 1 haemoglobin. The following table gives the proportion of haemoglobin, the normal amount of haemoglobin being taken as = 100: — Cytometer Scale. no 120 I30 I40 i bo 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 fluid becomes transparent. The quantity of haemoglobin is calculated from the thickness of the stratum of fluid required to correspond exactly to the colour-intensity of a coloured glass accompanying the instrument. The latter is coloured of a tint similar to a solution of haemoglobin, 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 cmm. blood with .5 cc. distilled water. In a few seconds a trans- parent solution of haemoglobin is obtained. 3. 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 diffuse white light. When the two colours appear 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 corresponding amount of haemoglobin. 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, 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 cmm. of blood, use 20 cmm. Graduation of the Chromometer. — 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 of the chromometer corresponds to the scale of the cytometer of the same blood. Suppose 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 haemoglobin, so that the chromometer number 140 must also be = 100. With the aid of the formula (p. 61) a similar table can be constructed for the chromometer. Suppose the blood investigated = 280 ; then by the aid of the formula and the data from normal blood we have : — , 100.140 14,000 e = ^2- = — if; — = 50. 280 280 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 haemoglobin ? VII.] ESTIMATION OF HEMOGLOBIN. 6$ If 130 (cytonieter) corresponds to 190 (chromometer), then no cytometer (i.e., graduation corresponding to ico parts of haemoglobin) correspond to x chromometer graduation : 190.no 20,000 , „ lip : 100= no : as.*, x = -y = — -?— =100.7. 130 130 Blood containing 100 parts haemoglobin will correspond 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 the glass is not necessarily the same in all. But it is easy to construct a scale for each instrument by investigating a specimen of blood and comparing it with the cytometer graduation as indicated in the foregoing paragraph. Precautions to be Observed in Using the Instrument. — The exact quantity of the several fluids must be carefully measured ; evaporation must be prevented by covering the blood-mixture. Further, do not look at the fluid too long at a time, as the eye becomes rapidly 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 leukaemia, 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 very dilute caustic potash. If the opacity does not dis- appear by the addition of this substance, then the opacity is due to the presence of fatty granules in the blood, so that by this means we can distin- guish liprcmia from leukaemia. Bizzozero claims that when the instrument is used as a cytometer the mean error is not greater than 0.3 per cent. 10. Preparation of Haemoglobin {dog's or horse's blood). — Centrifugalise filtered fresh defibrinated dog's blood, and when the corpuscles have subsided pour off the 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. The corpuscles swell up, become almost invisible, and the solution becomes clear. With the utmost care add, stirring all the time, I per cent, solution of acid sodic sulphate until the blood appears turbid like fresh blood. The stromata of the corpuscles are thereby caused to shrivel, and when they are centrifugalised for a long time, they run together, and can thus be separated. Pour oft' the clear fluid, cool it to o°, add one-fourth of its volume of pure alcohol previously cooled to o3 or lower. Shake up the whole, and let it stand for twenty-four hours at 5°-i5°. 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 per cent, alcohol and water. Redissolve the cr}Tstals in a small quantity, 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 Haemoglobin in Blood — Colorimetric Method (Hoppe- Seyler's 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.) The demonstrator will prepare a standard solution of haemoglobin of known strength [supra). 64 PRACTICAL PHYSIOLOGY. [VII. (6.) Spread a sheet of white paper on a table in a good light opposite a window, and on it place two haematinometers side by side (fig. 27, D). See that they are water-tight. If not, anoint the edges of the glass plates with 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 hsematinometers. (d. ) Weigh 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 hsematinometer (e.), and dilute the 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, Example (Hoppe-Seyler). — 20.186 grams of defibrinated blood were diluted with water to 400 cc. To the 10 cc. of this placed in a hsematinometer, 38 Fig. 35. — Zeiss's Microspectroscope after Abbe. Fig. 36.— Adjustable Slit in Fig. 35, A. 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 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 o. 145 grams of haemoglobin in 100 cc, so that the total amount of haemoglobin in the diluted blood is found, thus — IOO : 1920 : : 0.145 : x x = 2.784 grams. VIII.] SALIVARY DIGESTION. 65 Since, however, this amount of haemoglobin was obtained from 20.186 grama of the original blood, the amount in 100 parts will be found as follows : — 20.186 : IOO : : 2.784 : x x = 13.79 grams per cent. 12. Microspectroscopes. — "When very small quantities of fluid are fco b^ examined, they are placed in small vessels made by fixing short lengths of barometer tubing to a glass slide. Use either the instrument of Browning or that of Zeiss (figs. 35, 36). 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. 36). Within the. drum there is also a prism whereby light admitted at the side of the drum is totally reflected towards the eye of the observer. Above the eye-glass is placed an Amici prism of great dispersion, which turns aside on the pivot (K) to allow of the adjustment of the object. It is retained in position by the catch (L). At X is placed the scale of wave-lengths, and its image can be projected on the spectrum by the mirror (O). The scale is adjusted relative to the spectrum by the screw P. The scale is set by the observer so that Fraunhofer's line 13 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 water. Inhale the vapour of ether, glacial acetic acid, or even cold air through the mouth, which causes a reflex secretion of saliva. In doing so, curve the tongue so as to place its tip behind ,* ^^ the incisor teeth of the ]ift upper jaw. In a test-glass collect the saliva with as few air-bubbles as possible. If it be turbid or contain much froth, filteritthrough a small filter (p. 66). 2. I. Microscopic Exa- mination.— With a high power observe the presence of (1) squamous epithelium, (2) sali- vary corpuscles, (3) perhaps debris of food, (4) possibly air-bubbles, and (5) fungi — especially various forms of bacteria (fig. 37). E Fig. 37. — Microscopic Appearances of Saliva. 66 PRACTICAL PHYSIOLOGY. [VIII. II. Physical and Chemical Characters (sp. gr. 1 002-1 006). (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.) Test its reaction, neutral, or, as is more commonly the case, alkaline. (c.) Place a little mixed saliva in a test-tube, add dilute acetic acid = a precipitate of mucin. Filter. (d.) With the filtrate from (c), test for traces of proteids (serum-albumin and globulin) with the xanthoproteic reaction (Lesson I. 1, a), or by the addition of potassium ferrocyanide. ' (e.) To a few drops of saliva in a porcelain vessel add a few drops of dilute ferric chloride = a red colouration due to potassic sulpho-cyanide. The colour does not disappear on heating, or on the addition of an acid. The colour 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 potassic sulpho-cyanide to compare with (e.). (g.) The salts are tested for in the usual way (see "Urine "). Test for chlorides (HjST03 and AgN03), carbonates (acetic acid), and sulphates (barium chloride and nitric acid). (h.) Nitrites in Saliva (i.) are often present in saliva. Add a little of the saliva to starch paste, containing a little sulphuric acid and iodide of potas- sium, when, if nitrites be present, an intense blue colour is produced. (ii.) To diluted saliva add a few drops of sulphuric acid, and then meta- diamido-benzol. Yellow colour indicates the presence of nitrites. This reaction does not succeed in all cases. 3. Digestive Action. Starch Solution. — Place 1 gram of starch in a mortar, add a few cc. of cold water, and mix well with the starch. Add 200 cc. of boiling water, stirring all the while. Boil the|fluid in a flask for a few minutes. This gives a half per cent, solution. Do the tests for starch already described (Lesson III.), and especially satisfy yourself that no glucose or reducing sugar is present. Action of Saliva on Starch. (a.) Dilute the saliva with five volumes of water, and filter it. This is best done through a filter perforated at its apex by a pin- hole. In this way all air-bubbles are got rid of. Label three est-tubes A, B, and C. In A place starch mucilage, in B saliva, VIII] SALIVARY DIGESTION. 6? and in C. i volume of saliva and 3 volumes of starch mucilage. Plug all three with cotton-wool, and place them in a water-bath at 400 C, and leave them there for ten minutes. Test for a reducing sugar in portions of all three, by means of Fehlino-'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. (b.) 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. (c.) Make a thick 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. Notice that A is unaffected, while B soon becomes fluid — within two minutes — and loses its opales- cence ; this liquefaction is a process quite antecedent to the sac- charifying process which follows. 4. Stages between Starch and Maltose. — Mix some starch and saliva in a test-tube as in 3 (a.) C, and place it 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 bv means of another glass rod add a drop of iodine solution. Note the following stages : — At first there is pure blue 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 vel- lo wish-brown, and finally there is no reaction with iodine at all, achroo-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. 5. Effect of Different Conditions on Salivary Digestion. (a.) 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 starch mucilage and saliva, to B add a few drops of hydrochloric acid, and to C caustic potash. Place all three in a water-bath at 40° C, and after a time test them for sugar by Fehling's solution. No sugar is formed — in A because the ferment was destroyed 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 6S PRACTICAL PHYSIOLOGY. [VIII. prepared as in 3 (a.) G, and placed in a freezing mixtne, the conversion of starch into a reducing sugar is arrested; but the ferment is not killed, for on placing the test-tube in a water-bath at 40° C. the conversion is rapidly effected. (c.) Mix some raw starch with the saliva and expose it to 400 C. Test it after half an hour or longer, when no sugar will be found. 6. Starch is a Colloid, but Sugar is a Crystalloid and dialyses. (a.) Place in a short piece of the sausage parchment tube, already referred to (p. 3), 20 cc. of starch mucilage, label it A, and into another, some starch mucilage with saliva, label it B. Suspend A and B in distilled water in separate vessels. (5.) 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 con- verted into a readily diffusible body during digestion. 7. Action of Malt-Extract on Starch. (a.) Rub up 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 low-dried malt, and extract it for half an hour with 30 cc. of distilled water, and filter. Keep the filtrate. (c.) Place the starch paste of (a.) in a flask, and cool to 6o° C, add the extract of (&.), and place the flask in a water-bath at 6o° C. (d.) 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. (e.) Take a portion and precipitate it with alcohol = achroo- dextrin. (/.) Boil the remainder of the fluid, cool, filter, and evaporate the filtrate to 20 cc. Add 6 volumes of 90 per cent, spirit to precipitate the dextrin, boil, filter, and concentrate to dryness on a water-bath, and dissolve the residue in distilled water. The solution is maltose (C12H22On + H20). If the alcoholic solution be exposed to air, crystals of maltose are formed. IX.] GASTEIC DIGESTION. 69 ADDITIONAL EXERCISES. 8. Compare the Reducing Power of Maltose and Dextrose. a.) With Fehling's solution estimate the reducing power of the solution obtained in 7 (/.). (See "Urine.") (6.) Boil in a flask 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 determine by Fehling's solution the reducing power. The acid has converted the maltose into dextrose, and the ratio of the former estimation («.) to the present one should be 66 to 100. (c.) A solution of pure dextrose treated as in (b.) is not affected in its reducing power. Saliva has practically the same effect on starch as malt-extract, and may be used instead of the latter. 9. Tetra-Paper, and Oxidising Power of Fluids, e.g., Saliva. — The papers known as tetra-paper are used to estimate the oxidising power of a fluid, such as saliva. They are impregnated with tetra-methyl-paraphenylene-diamine. This body with 1 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 this the basis for the measurement of the oxidising power of fluids, 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 supplied with the tetra- papers are obtained by means of a solution of iodine. A certain depth of tint on the scale corresponds to a certain amount of active oxygen (ozone) per litre of the fluid. The papers and scale are supplied by Dr. Theodor Schuchardt, Gorlitz. (a.) Fold the paper and place 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.g., saliva, to run on the paper. Compare the colour of the paper 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. (<7.) Take a part of the cardiac end of the pig's stomach pro- vided for you, which has been previously opened and washed rapidly in cold water. Spread it, mucous surface upwards, 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 with fine sand. Add water, and rub up the whole vigorously for some time, and filter. The filtrate is an artificial gastric juice. JO PRACTICAL PHYSIOLOGY. [IX. (b.) V. Wittich's Method. — From another portion of the car- diac end of a pig's stomach detach the mucous membrane in shreds, dry them between folds of blotting-paper, place them in a bottle, and cover them with strong glycerin, letting them stand for eight days. The glycerin dissolves out the pepsin, and on filtering, a glycerin extract with high digestive properties is obtained. (c.) Kuhne's Method. — Take 130 grams of the cardiac mucous membrane of a pig's stomach, and place it in 5 litres of water containing 80 cc. of 25 per cent, hydrochloric acid (i.e., .2 per cent.). Heat the whole for twelve hours at 400 C. Almost all the mucous membrane is dissolved. Strain through flannel and then 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 preparation of gastric juice is that a thread of fibrin when placed in the fluid and warmed should be dissolved in a few minutes. (d.) Instead of (a.) and (b.) it is convenient to use Benger's liquor pepticus, or the pepsin preparation of Burroughs, Well- come, & Co. All the above artificial juices, when added to hydrochloric acid of the proper strength, have high digestive powers. 2. Both Hydrochloric Acid and Pepsin are required for Gastric Digestion. (a.) Take three beakers or large test-tubes, label them A, B, C. Put into A some 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. h}7drochloric 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. (b.) Examine them. In A, the fibrin is unchanged; in B, the fibrin is swollen up; while in C, it has disappeared, having first become swollen up and clear, and finally completely dissolved, being converted into peptones. Therefore, both acid and ferment are required for gastric digestion. The following table shows the results obtained, all the tubes being kept at a temperature of 40° C. : — Tube A. Tubk B. Tube C. Water. Pepsin. Hydrochloric acid. Fibrin. Water. Pepsin. Fibrin. Water. Hydrochloric acid. Fibrin. IX] GA.STRIC DIGESTION. 71 After Twenty Minutes. Tube A. Tube B. Tube C. Unchanged. Fibrin begins to swell up, becomes clear, and small quantity of acid albu- min or syntonin formed. Acid albumin formed (pre- cipitated on neutrali>a- tion), some albumoses formed (precipitated bv (XH4).S04), and very small quantity of pep- tones. After One Hour. Unchanged. Somewhat more syntonin formed. Small amount (or no) syn- tonin ; albumoses, and much peptone. 3. To Prepare Hydrochloric Acid of 0 2 per cent. — Add 6.5 cc. of ordinary commercial hydrochloric acid to 1 litre of distilled water, and shake together. 4. Products of Peptic Digestion and its Conditions. (a.) Take three large test-tubes, labelled A, B, C, and fill each one half full with hydrochloric acid 0.2 per cent. ; or use cylin- drical vessels with a thick base, such as are used for anatomical preparations. Fig. 38 shows a convenient form of water- bath, heated by a rat-tailed gas - flame. Add to each 5 drops of a glycerin extract of pepsin. Boil B, and make C faintly alkaline with sodic car- bonate. The alkalinity may be noted by adding previously some neutral litmus solution. Add to each an equal amount — a few threads of well-washed fibrin — which has been pre- viously steeped for some time FlG. 3 _Digestion-Bath. in 0.2 per cent, hydrochloric acid, so that it is swollen up and transparent. Keep the tubes in a water-bath at 400 C. for an hour, and examine them at intervals of twentv minutes. 72 PRACTICAL PHYSIOLOGY. [IX. (b.) After five to ten minutes, or less, the fibrin in A is dis- solved, 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. (c.) Carefully neutralise the filtrate of A with dilute caustic soda. The filtrate becomes turbid and gives a precipitate of acid-albumin or syntonin. Filter off this precipitate, dissolve it in 0.2 per cent, hydrochloric acid. It gives proteid reactions (Lesson I. 7). (d.) Test the filtrate of (c.) for liemi-albumose. Repeat all the tests for hemi-albumose (Lesson I. 10, VI.). Hemi-albumose is soluble in water, and gives all the ordinary proteid reactions. It is precipitated by nitric acid in the cold, but the precipitate is redissolved with the aid of heat. Hemi-albumose 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 a rosy-pink with the biuret test. Like peptones, it is soluble in water. (e.) To part of the filtrate of (c.) 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, VI.). (/.) 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 the remainder of C acid be added, and it be placed again at 400 C, digestion takes place, so that neutralisation has not destroyed the activity of the ferment. 5. Repeat the Tests for Hemi-Albumose (Lesson I. 12), noting specially that it is precipitated by the following sub- stances : — Nitric acid, acetic acid and NaCl, acetic acid and ferrocyanide of potassium, and also that the precipitates are soluble on heating and reappear on cooling. It also gives a precipitate with solid metaphosphoric acid. In all these respects it differs from peptone. Like peptone, however, it gives a rosy- pink with the biuret reaction. 6. Repeat the Tests for Peptones (Lesson I. 10, VI.). IX.] GASTRIC DIGESTION. 73 ADDITIONAL EXERCISES. [Proteids, e.g., 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. p. s < " Anti-albumose. Hemi-albumose. Anti-peptone. Anti-peptone. Hemi-peptone. Hemi-peptone. Leucin, Tyrosin, Leucin. Tyrosin, ^ &c. &c. The anti-group is not further split up, bat the hemi-group, although not split up by peptic digestion, is split up by tryptic digestion into leucin, tyrosin, and other products. The substance hitherto called hemi-albumose has been shown bv Kiihne to consist of three albumoses, viz., proto-albumose. hetero-albumose. and deutero-albumose. The first two are precipitated by NaCl. and the last by NaCI and acetic acid. The separation of these bodies— which can be obtained most easily from Witte's peptone — hardly falls within the scope of this work. 7. To Prepare Hemi-Albumose and Gastric Peptones in Quantity. (a.) Place 10 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 supported erect in it. (b.) Add I or 2 cc. of glycerin pepsin extract or the artificial gastric juice, 1 (&), and stir the mass. Within a few minutes the whole becomes fluid. (c. ) After a short time — fifteen to twenty minutes — before the peptonisatinn is complete, filter and exactly neutralise the filtrate with ammonia or caustic soda, which precipitates the acid albumin or syntonin with a small quantity of the albumoses. 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 dialvser (fig. 39)-] 8. Action of Gastric Juice on Milk. (a.) Place 5 cc. of fresh milk in a test-tube, and add to it a few drops of a neutral artificial gastric juice. Mix and keep at 40° C. In a short time the milk curdles, so that the tube can be inverted without the curd falling out. By-and-bv whey is 74 PRACTICAL PHYSIOLOGY. [IX. squeezed out of the clot. The curdling of milk by the rennet ferment present in the gastric juice is quite different from that produced by the/' souring of milk " or by the precipitation of casein by acids. Here the casein (carrying with it most of the fats) is precipitated in a neutral fluid. (b.) 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 the acid digests the casein, gradually dis- solving it, forming a straw-yellow-coloured fluid containing peptones. The " pepto- nised milk " has a peculiar odour and bitter taste. (c. ) To 5 cc. of milk in a test-tube add a few drops of Benger's liquor pepticus, and place in a water-bath. Observe how the casein first clots, and is then partially dis- solved to form a yellowish-coloured fluid, with a bitter taste and peculiar odour. There generally remains a very consider- able clot of casein ; and, in fact, the gastric fig. 39.-Kuhne's Diaiyser. digestion of milk is slow, especially if com- a parchment tube, such as pared with its tryptic digestion (Lesson X. %^gSSZK&£* 11). Test the fluid for peptones with which water is^ kept con- the biuret test, and observe the beautiful light-pink colour obtained. The bitter taste renders milk "peptonised" by gastric juice unsuitable for feeding purposes. 9. Action of Rennet on Milk. (a.) Place some milk in a test-tube, label it A, add a drop or two of rennet, shake it up, and place the tube in a water-bath at 40° C. Observe that 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 same experiment, but previously boil the rennet. No such result is obtained as in (a). 10. 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 far stronger organic acid does not affect its colour. IX.] GASTRIC DIGESTION. 75 (b.) Repeat (a.), 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. 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. (c.) Repeat (a.) with the same acids, but use threads or paper stained with congo-red, and observe the change of colour to blackish-blue or blue produced by the hydrochloric acid. {d. ) Phloro Glucin and Vanillin (Giinzburg). — Dissolve 2 grams of phloro- glucin and I gram of vanillin in 100 cc. alcohol. Mix equal quantities of this with the fluid to be tested, and evaporate the mixture in a watch-glass on a water-bath. Do not allow the fluid to boil. The presence of HC1 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. HC1, and is said not to be impeded by organic acids, albumin, or peptone. (e.) Benzo-Purpurin 6 B. — Use blotting-paper soaked in a saturated watery solution of this fluid and dried. HC1 (.4 grin, in 100 cc. ) makes them dark blue, while organic acids make them brownish-violet. If both HC1 and organic acids be present, the stain is brownish-black ; but if the stain be suspected to be partly due to HC1, wash the paper in a test-tube with sulphuric ether, which removes the stain due to the organic acid, leaving that due to the HC1 unaffected. The sulphuric ether does not affect the mineral acid stain. (/.) 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 drops of the gastric juice to mix with it = a li^ht violet colour at the point of contact, and a mahogany brown when the fluids mix. It is less sensitive than the aniline tests. (g.) Shake up a mixture of dilute HC1 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 sometimes used clinically for ascertaining the presence or absence of hydrochloric acid, e.g., in a vomit. This acid is almost invariably absent from the gastric juice in cancer of the stomach. It is to be noted, however, that the presence of pep- tones interferes with the delicacy of some of these reactions. The reactions (c), (d.), (e.) are the most to be depended on. 11. Carbolo- Chloride of Iron Test for Lactic Acid (Uffelmann). — Prepare a fresh solution by mixing 10 cc. of a 4 per cent. 76 PKACTICAL PHYSIOLOGY. [X. solution of carbolic acid with 20 cc. of distilled water, and 1 drop of liquor ferri perchloridi. The amethyst- blue solution thus obtained is changed to yellow by lactic acid, while it is not affected by o. 2 per cent. HC1 ; 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 HC1, acetic, or butyric acid, but it is intensified in the presence of dilute lactic acid. 12. Chemical Examination of the Gastric Contents, e.g., Vomit. (a.) Test the reaction. {b.) Determine the acidity {e.g., of 10 cc.) by means of a deci-normal solution of caustic soda. (See "Urine.") (c.) Test 10 cc. for the presence of pepsin (digest with fibrin and HC1), and rennet (milk). (d.) Use the tests 10 (c), (d.), (e.) for determining the presence of free HC1. (e.) Make a rough estimate of the presence of lactic, butyric, and acetic acids by the method 10 (g.). (/.) Examine for proteids, e.g., albumin, albumoses, and peptone. (g.) Test for sugar and its digestive products. {h.) Distil some of the fluid, extract the remainder with sulphuric ether, and in the latter estimate the lactic acid which it contains. LESSON X. PANCREATIC DIGESTION. 1. Preparation of Artificial Pancreatic Juice. (a.) Use part of the pancreas of an ox twenty-four hours after the animal was killed. Mince a portion of the pancreas, 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 ceijt. 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. (6.) Make a glycerin extract of the pancreas (pig) in the same way as described for the stomach (Lesson IX. 1, b). Before putting it in glycerin, it may be placed for two days in absolute alcohol to remove all the water. This extract acts on starch and proteids. X.] PANCREATIC DIGESTION. J J (c.) For most experiments it is more convenient to use the excellent pancreatic extracts now supplied by Mr. Benger of Manchester as "liquor pancreaticus,'' or those of Messrs. 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 io 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. | Kuhne'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. Extract the dry pan- creas powder with five parts of a .2 per cent, solution of salicylic acid, and keep it about 400 C. for eight or ten hours. Use 20 grams of the dry pancreas to 100 cc. of the salicylic acid fluid. Strain it through muslin, and press out all the fluid from the residue. The hands must be well washed, as pan- creatic 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 400 C. with sodic carbonate solution (.25 per cent.), adding a few drops of alcoholic solution of thymol. Filter the first extract and allow it to stand. Very probably a large mass of crystals of tyrosin will separate. Filter oft' the deposit and mix the salicylic and alkaline extracts. The extract has only proteolytic properties. I find this extract acts much more energetically than those prepared in other ways. What remains after the action of salicylic acid and sodic carbonate contains leucin and tyrosin. 2. I. Action on Starch. (a.) Take thick starch mucilage in a test-tube or beaker, add glycerin extract of pancreas or liquor pancreaticus, and place it in a water-bath at 400 C. Almost immediately the starch paste becomes fluid, loses its opalescence, and becomes clear. Within a few minutes much of the starch is converted into a reducing sugar or maltose. (b.) Test for sugar (Lesson III. 8, V.). 3. The same conditions obtain as for saliva (Lesson VIII. 5). 4. II. Proteolytic Action due to Trypsin, and its Conditions. (a.) Take three test-tubes, labelled A, ft$, and C, fill each half full with 1 per cent, solution of sodic •carbonate, and place 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 400 C. (b.) Examine them from time to time. At the end of one, two, or three hours there is no change in B and 0, while in A 7 8 PRACTICAL PHYSIOLOGY. [X. 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-albu- min. Filter off the precipitate, and on testing the filtrate, pep- tones 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 "pan- creas powder" (Lesson X. 1, 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 peptones. It is difficult to get any albumoses after this time; the anti-albumoses are already converted into anti-peptones, the hemi-albumose into hemi-peptone, and some of the latter is decomposed into leucin and tyrosin. 5. Products other than Peptones — Leucin and Tyrosin. (a.) Place 300 cc. of a 1 per cent, solution of sodic carbonate in a flask, add 5 grams of boiled fibrin, 5 cc. of glycerin extract of pancreas, and a few drops of an alcoholic solution of thymol. Keep all at 38° C. on a water-bath for six to ten hours. (b.) After six 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 considerable volume of alcohol. Filter to remove the peptones, and evaporate the alcoholic filtrate to a small bulk, and set it aside, when leucin separates first, and crystals of tyrosin after- wards. Keep them for microscopic examination (figs. 5, 73). (c.) A much better method of obtaining leucin and tyrosin is to digest, at 40° C, for five or six hours, equal parts of fresh moist fibrin and ox- pancreas with a sufficient quantity of thy- molised water. Boil part of the liquid, and evaporate a small quantity of it, or merely place a drop on a glass slide and allow it to evaporate, when beautiful microscopic crystals of leucin and tyrosin are obtained. Continue the digestive process of the remainder of the liquid for a few hours, until the mixture emits a very disagreeable odour. This fluid gives the chlorine and indol reaction splendidly. (d.) Examine the crystals of leucin and tyrosin microscopi- X] PANCREATIC DIGESTION. 79 cally. The former occurs as brown balls, often with radiating lines, not unlike fat, but much less refractive, and the latter consists of long white shining needles arranged in a stellate manner, or somewhat felted. (See "Urine," fig. 73.) (e.) Test for Tyrosin (Hofmann). — Dissolve some crystals by boiling them in water, add Millon's reagent, and boil, which gives a rosy-red colour. (/'.) Test a solution of tyrosin, obtained by the prolonged boil- ing of horn-shavings and sulphuric acid, with Millon's reagent, as in (e.) The deposit which is sometimes formed in Benger's liquor pancreaticus consists of tyrosin. 6. Putrefactive Products of Pancreatic Digestion. — These include indol, skatol, phenol, volatile fatty acids, C02, H.,S, CH4, and H. CH = CH Indol C6H4 ^^ = C8H7N and yC.CH3 = CH Skatol C6H4' =C0H9X. NH Indol appears in a pancreatic digest as one of the many putrefactive pro- ducts of the decomposition of proteids. Take equal parts of fresh fibrin and finely-divided ox-pancreas, add ten times the volume of water, and keep the whole continuously at a temperature 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 dissolved in water, is allowed to crystallise. The solution yields the following tests. Tests for Indol. — Use either the 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 Kiihne'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. (b.) 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 hydrochloric 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 (6, a, or preferably 6), drop by drop, chlorine water; it strikes a beau- SO PRACTICAL PHYSIOLOGY. [X. tiful rosy-red tint. Or add very dilute bromine water (i to 2 drops to 60 cc. water), the fluid first becomes pale red, then violet, and ultimately deep violet (Kuhne). 7. III. The Action on Fats is Twofold. (A.) Emulsification. (a.) Hub 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 pancreas, and do likewise ; but in this case the result will not be nearly so satisfactory. (b.) Rub up oil as in (a.) ; but this time use an extract of the fresh pancreas made with 1 per cent, sodic carbonate. A very perfect emulsion is obtained, even if the sodic carbonate extract is boiled beforehand. This shows that its emulsifying power does not depend on a ferment. (c.) The presence of a little free fatty acid greatly favours emulsification. Take two samples of cod-liver oil, one perfectly neutral (by no means easily procured), and an ordinary brown oil — e.g., De Jongh's. The latter contains much free fatty acid. Place 5 cc. of each in two test-tubes, and pour on them a little solution of sodic carbonate (1 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 contain free fatty acids, and only some of them give up their acid to water, just according as the fatty acid is soluble in water or not. 8. (B.) The Fat-Splitting Action of Pancreatic Juice. (a.) Prepare a Perfectly Neutral Oil. — A perfectly neutral 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 from the insoluble portion, and the ether evaporated over warm water. The oil should now be perfectly neutral (Krukenberg). (b.) Mix the oil with finely-divided, perfectly fresh pancreas (not a watery extract), and keep it at 400 C. After a time its reaction becomes acid, owing to the formation of a fatty acid. This experiment is by no means easy to perform, and some observers deny altogether the existence of a fat- splitting ferment. The 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 prepared for you to 5 cc. of warm milk in a test-tube, and keep it at 400 C. Within a few minutes a solid coagulum forms, and thereafter the whey begins to separate. X.] PANCREATIC DIGESTION. 8 1 (b.) 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 instantly destroyed. 10. Action on Milk. (a.) Dilute cow's milk with 5 volumes of water. Test a por- tion, and note that acetic acid throws down a flocculent pre- cipitate of casein. Place some of the diluted milk in a test-tube, add a drop or two of pancreatic extract, or the liquor pancrea- ticus of Benger. Expose on a water-bath at 40° C. for half an hour. Note that the casein is first curdled and then dissolved, and as this occurs, the milk changes from a white to a yellowish colour. (h.) Divide the fluid of (a.) into two portions, A and B. To A add dilute acetic acid ; there is no precipitation of casein, which has been converted into peptones. To B add caustic soda and dilute copper sulphate, which give a rose colour, proving the presence of peptones. 11. To Peptonise Milk. — A pint of milk is diluted with a quarter of a pint of water, and heated to a lukewarm tempera- ture, about 1 40° F. (or the diluted milk may be divided into two equal portions, one of which 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 unobjectionable to many palates; a few trials will, how- ever, 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 EXERCISE. 12. Preparation of Indol. — Place 1 kilogram of fresh fibrin in a 6-litre jar with 4 litres of water (to which I gram KHPO4 and .5 grain MgS()4 are added). Mix this with 200 cc. cold saturated solution of scdic carbonate, and add to the whole a quantity of putrefying Mesh-juice and some pieces of the F §2 PRACTICAL PHYSIOLOGY. [XL putrid flesh as well. Cork the vessel, a vent-tube being placed in the cork, and place it aside for 5-6 days at a temperature of 40-420 C. Distil and acidify the strongly ammoniacal distillate with HC1, 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 addi- tion 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. (Drechsel after Salhowski.) LESSON XI. THE BILE. 1. Use ox- bile obtained from the butcher. (a.) Observe the colour of bile of man and that of the ox; the former is a brownish-yellow, the latter greenish, but often it is reddish-brown when it stands for a short time. (b.) Dilute bile and test its reaction = alkaline or neutral. (c.) Pour some ox-bile from one vessel to another, and note that it is sticky, strings of mucin connecting the one vessel with the other. (d.) Dilute bile with 5 volumes of water, add dilute acetic acid, which precipitates the mucin coloured with the pigments. Or dilute bile with its own volume of water, and precipitate the mucin with alcohol. Filter, and observe that the filtrate is no longer sticky, but flows like a watery non-viscid fluid. The mucin remaining on the filter may be washed with dilute spirit and dis- solved in lime-water. It gives the xanthoproteic reaction, and that with Millon's reagent, but not that with cupric sulphate. (e.) Bile gives no reactions for albumin. (/.) Fresh human bile gives no spectrum, although the bile of the ox, mouse, and some other animals does. (g.) Bile, besides the ordinary salts, contains so much iron as to give the ordinary reactions for iron. To bile add hydrochloric acid and potassic ferrocyanide. A blue colour indicates the presence of iron. It is better to use the filtrate of (d.) free from mucin. If fresh bile is not obtainable, use a watery solution of the " Fel bovinum " of the Pharmacopoeia. 2. To Prepare the Bile- Salts or Bilin (glycocholate and tauro- cholate of sodium). XL] THE BILE. 83 (a.) Mix ox-bile with animal charcoal in a mortar to form a thick paste. Evaporate to complete dryness over a water- bath. Keep this for preparing an alcoholic solution of the bile- salts. (b.) Take some of the dry charcoal-bile mixture, and add five times its volume of absolute alcohol. Cork the flask or test-tube in which the mixture is placed. Shake up 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 water be present, sometimes the bile-salts are thrown down crystalline; but not unfrequently 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 large glancing needles which constitute Plattner's Crystal- lised Bile. 3. Pettenkofer's Test for Bile-Acids and Cholic-Acid. (a.) Place some bile in a test-tube, add a drop or two of syrup of cane-sugar, and mix. Pour in concentrated sulphuric acid, and at the line of junction of the two fluids a purple colour is obtained. The white deposit seen above the line of junction is precipitated bile-acids. They are insoluble in water. (b.) Or, after mixing the syrup with the bile, add the strong sulphuric acid drop by drop, mixing it thoroughly. Heat gentlv, and the fluid becomes a deep purple colour. Take care not to add too much syrup, and not to overheat the tube. If the requisite amount of sulphuric acid be added, the temperature becomes sufficiently high (700 C.) without requiring to heat the tube. (c.) A better way of doing the test is as follows : — 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. (d.) It may also be done by mixing a few drops of bile in a porcelain capsule with a small crystal of cane-sugar, and, after the sugar is dissolved, adding sulphuric acid drop by drop. (e.) Strasburg's Modification (e.f/.. 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. (/) Eepeat any or all of the above processes with a watery solution of the bile-salts. 4. Similar colour reactions are obtained with many other sub- stances— e.g., albumin and fats. 84 PKACTICAL PHYSIOLOGY. [XL Albumin and Sulphuric Acid. — To a solution of syntonin and syrup add strong sulphuric acid, and a similar tint is obtained. The spectra, however, are different, the red-purple fluid from bile gives two absorption-bands, one between E and E, and another between D and E. In the albuminous solu- tions only one absorption-band exists between E and E. 5. Action of Bile or Bile-Salts in Precipitating Sulphur. (a.) Take two beakers, and in one (A) place diluted bile, and in the other (B) water. Pour flowers of sulphur on the surface of the water of both. The sulphur falls in a copious 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.) Perform the same experiment with a solution of the bile- salts. Bile-Pigments. — The chief are bilirubin (red), biliverdin (green), and urobilin. 6. G-melin's Test for the Bile -Pigments. (a.) Place a few drops of bile on a white porcelain slab. With a glass rod place a drop or two of strong nitric acid containing nitrous acid near the drop of bile, bring the acid and bile into contact, when there is immediately a play of colours, beginning with green and passing into blue, violet, red, and dirty yellow. (b.) Place a little nitric acid in a test-tube. Slant the tube and pour in bile, a similar play of colours occurs — green above, blue, violet, red, and yellow below. It is better to do this re- action 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. (c.) For a modification applicable to urine, see " Urine." 7. Cholesterin and Gall-Stones. (a.) Preparation. — Powder a gall-stone and extract it with ether. Heat the test-tube with ether in warm water, and see that no gas is burning near it. Allow a drop of the ethereal solution to evaporate on a glass-slide or watch-glass, and examine the crystals under the microscope. They are flat plates, with an oblong piece cut out of one corner (fig. 40). (&. ) Heat a few 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. (It requires a little practice to get this test always to succeed.) (c.) Dissolve some crystals in chloroform, add an equal volume XL] THE BILE. 85 FIG. 40.— Crystals of Cholesteriu. of concentrated sulphuric acid, and shake the mixture. "When the chloroform solution floats on the top, it becomes blood-red, but changes quickly on exposure to the air, passing through violet and blue to green and yellow. A trace of water decolorises it at once. The layer of sulphuric acid shows a green fluorescence. (d.) The crystals when acted on by strong sulphuric acid become red. Do this on a slide under the microscope. (e.) Place a crystal on a piece of porcelain, add a drop of strong nitric acid, evaporate to dryness at a gentle heat, until a yellow re- sidue is obtained. A drop of ammonia strikes a red colour, which is not altered by the addi- tion of caustic soda. (/.) Examine microscopically crystals of cholesterin floating in hydrocele fluid. The crystals may not be quite perfect, but their characters are quite distinct. 8. Action of Bile in Digestion. (a.) Action on Starch. — Test if bile converts starch mucilage into a reducing sugar, as directed for saliva (Lesson VIII. 3). (6.) Action on Fats. — Mix 10 cc. of bile with 2 cc. of almond- oil or oleic acid. Shake them together, 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 he obtained. In the latter the oil and water separate almost imme- diately. (c.) Mix 10 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 decompose 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 soap 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. (d.) Favours Filtration and Absorption. — Place two small funnels exactly the same size in a lilter-stand, and under each a beaker. Into each funnel put a filter-paper ; moisten the one with water (A), and the other with bile (B) ; pour into both an equal volume of almond-oil : cover with a slip of glass to prevent evaporation. Set the whole aside for twelve hours, and note that the oil passes through the filter B, but scarcely any through A. S6 PRACTICAL PHYSIOLOGY. [XII. (e.) Effect on the Proteid Products of Gastric Digestion. — Digest some fibrin in artificial gastric juice, filter, and to the filtrate add drop by drop some ox-bile, or a solution of bile-salts. It causes a white precipitate of peptones and parapeptones. The acid of the gastric juice splits up the bile-salts, so that the bile acids are also thrown down. (/.) Action on Syntonin. — Prepare syntonin in solution (Lesson I. 7. III.)? ana* add a few drops of bile or bile-salts. It causes a curdling of the whole mass. Be careful not to add too much bile. In (e.) and (/) it is better to add the bile-salts, because the free hydrochloric acid gives a precipitate with bile. deposit, and evaporate the mixture- ADDITIONAL EXERCISES. 9. Preparation of Taurin (/3-amidosethyl-sulphuric acid C2H7NS03). — Mix ox-bile with an excess of strong hydrochloric acid, filter from the slimy -just imder boiling-point — whereby a tough brownish resinous body sepa- rates— choloidinic acid. Pour off the acid watery fluid, concentrate it still further, until the greater part of the common salt crystallises out. Mix the cold mother-liquid with strong 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 powdered pale gall-stones in water, and then extract them with boiling alcohol. Filter through a double- walled filter kept hot with boiling water (fig. 41). The filtrate on cooling precipitates cholesterin. Recrystallise it from boiling alcohol containing potash, with alcohol and water, and dry the residue over sulphuric acid Fig. 41.- -Double-Walled Filter for Filtering Hot Solutions. impure wash it (fig- 2). LESSON XII. GLYCOGEN, IN THE LIVER. 1. Preparation. («.) Boil some water slightly acidulated with acetic acid, and keep it boiling. Feed a rat, and three or four hours thereafter decapitate it. Rapidly open the abdomen, remove the liver, cut XII] GLYCOGEN IN THE LIVER. Sy one half of it in pieces, and throw it into the boiling acidulated water. Lay the other half aside, keeping it raoist in a warm place for some hours. After boiling the first portion for a time, pound it in a mortar with sand, and boil again. Filter while hot. The filtrate is milky or opale*<:trd, and is a watery solution of glycogen. The acetic acid coagulates the proteids, while the boiling water destroys a ferment in the liver, which would con- vert the glycogen into grape-sugar. (b.) Brucke's Method. — Feed a rabbit on carrots, and after from two to three hours decapitate it. Open the abdomen, tear out the liver, cut it rapidly in pieces, and take one half — lav- ing the other half aside as in (a.) — throw it into boiling water, boil it, aud afterwards pound it in a mortar and boil again. Filter while hot, and observe the opalescent liltrate, which is a solution of glycogen and proteids. The nitrate should flow into a cooled beaker, placed in a mixture of ice and salt. Precipitate the proteids by adding alternately hydrochloric acid and potassio- mercuric iodide, until all the proteids are precipitated. Filter off the proteids, and the beautiful opalescent filtrate is an imperfect solution of glycogen. The glycogen is precipitated by adding 96 per cent, alcohol until the solution contains over 60 per cent, of alcohol. (c.) Kulzs Method. — Feed a large rabbit for two days on carrots or boiled rice. Three or four hours after the last full meal decapitate the animal, 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 rubbing with well-washed white sand). Replace the pulp in the boiling water and add 3-4 grams of caustic potash {i.e., for ico grams liver). Heat on a water-bath and evaporate until about 200 cc. of fluid remains for 100 grams liver. If a pellicle forms on the surface, heat the whole in a beaker covered with a watch-glass until the pellicle is dissolved. Allow to cool. Neutralise with dilute hydrochloric acid aud 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 filter to remove the deposit of proteids. Remove the deposit from the filter with a spatula, and rub it up 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 L.\vco£en. 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 96 per cent, alcohol. Usually the glycogen contains a trace of albumin. To remove the latter, re- dissolve the moist glycogen in warm water, and after cooling, reprecipitate with HC1 and potassio-mercuric iodide and proceed 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 results. (d.) Instead of a rat or rabbit's liver, use oysters or the edible mussel, and prepare a solution of gbycogen by methods (a ) or (//.). 88 PRACTICAL PHYSIOLOGY. [XII. (e.) Use the other half of the liver of the rat or rabbit that has been kept warm, and make a similar extract of it. 2. Precipitate the Glycogen. — Evaporate the nitrate of (a.) or (b.) to a small bulk, and precipitate the glycogen as a white powder by adding a large amount of alcohol. 3. Preparation of Potassio-Mercuric Iodide. — Precipitate a saturated solu- tion 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. (a.) To the opalescent nitrate add a solution of iodine = a port- wine red colour (like that produced by dextrin). If much gly- cogen be present the colour disappears, and more iodine has to be added. Heat the red fluid ; the colour disappears on heating, but reappears on cooling. N.B. — In performing this test, make a control- experiment. Take two test-tubes, A and B. To A add solution of glycogen ; to B, an equal volume of water. To both acid the same amount of iodine solution. A becomes red, while B is but faint yellow. (b.) Test a portion of the glycogen solution for grape-sugar. There should be none, or only the faintest trace. (c.) To a portion (A) of the glycogen solution add saliva or liquor pancreaticus, and to another portion (B) add blood, and place both on a water-bath at 40° C. After ten minutes test both for sugar. (A) will now be transparent, and give no re- action with iodine. Perhaps both will give the 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. (d.) Boil some glycogen solution with dilute hydrochloric acid in a flask; neutralise with caustic soda, and test with Fehling's solution for sugar. (e.) To another portion add plumbic acetate = a precipitate (unlike dextrin). (/.) To another portion add plumbic acetate and ammonia = a precipitate (like dextrin). 5. Test the watery extract of the second half of the liver (d). (a.) It will perhaps give no glycogen reaction, or only a slight one. (b.) It contains much reducing sugar. 6. Extract of a Dead Liver. (a.) Mince a piece of liver from an animal (e.g., an ox) which has been dead for twenty-four hours. Place the finely-divided liver in water or in a saturated solution of sodic sulphate, and XIII.] MILK, FLOUR, AND BREAD. 89 boil to make a watery extract. Filter, and observe the filtrate ; it is clear and yellowish in tint, but not opalescent. (b. ) Test its reaction = acid. (c.) Test with iodine after neutralisation with sodic carbonate and filtration = no glycogen. (d.) Test for grape-sugar = much sugar. After death the glycogen is rapidly transformed into grape- susrar. LESSON XIII. MILK, FLOUR, AND BREAD. 1. Milk. — Use fresh cow's milk. (a.) Examine a drop of milk under the microscope, noting the numerous small, highly-refractive fat globules floating in a fluid (fig. 42, M). (i.) Add a drop of dilute caustic soda, and observe how the globules run into groups. (ii.) To a fresh drop add osmic acid, and observe how the globules first become brown and then black. (iii.) If a drop of colos- trum is obtainable, examine for the " colostrum corpus- cles " (fig. 42, C). (h.) Examine the " naked- eye" characters of milk. (c.) Test its reaction with litmus-paper. It is usually alkaline. (d.) Take the specific gra- vity of perfectly fresh un- skimmed milk with a hyd- rometer or lactometer. It is usually between 1025- 1030. Take the specific gravity next day after the cream has risen to the sur- face. The specific gravity is higher. (e.) Dilute milk with ten times its volume of water, and care- fully neutralise it with dihti<> acetic acid, observe that there is no precipitate, as the casein is prevented from being precipitated by the presence of alkaline phosphates (Lesson I. 7). Cautiously Fig. 42. — Microscopic Appearance of Milk. The upper half, M, is milk; the lower half, colos- trum, C. 90 PRACTICAL PHYSIOLOGY. [XIII. add the acetic acid until there is a copious granular-looking pre- cipitate of casein, which, as it falls, entangles the greater part of the fat in it. If desired, the precipitation is hastened by heating the fluid to 70° C. (/.) Filter (e.) through a moist plaited filter. Keep the residue on the filter. The filtrate of (/.) should be clear. Divide it into two portions. Take one of the portions, divide it into two, and boil one = a precipitate of lact albumin (serum-albumin). Filter, and keep the filtrate to test for sugar. To the remainder add potassic ferrocyanide, which also precipitates serum-albumin. (g.) With the second half of the filtrate test for milk-sugar or lactose with Fehling's solution, or by Trommer's test (Lesson III. 8. V.). Instead of proceeding thus, test for the presence of a reducing sugar with the filtrate of (/.) after the separation of the serum-albumin. (li.) 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 does not do so. 2. Separation of the Casein by Salt. — To 1 volume of milk in a test-tube add 2 volumes of a saturated solution of common salt, and then excess of powdered salt (or magnesic sulphate may be used). Shake the tube vigorously for a time, _Jk, when the casein and fat separate out, rise to the I surface, and leave a clear fluid or whey behind. - — -^ j This fluid contains the lactose, salts, and serum- JLjl albumin. 3. Separation of the Casein and Fat by Filtration. — Using a Bunsen's pump, filter milk through a porous cell of porcelain. The particulate matters — casein and fat — remain behind, while a clear filtrate containing the other substances in milk passes through. The porous cell is ^sHP^ left einpty and fitted with a caoutchouc cork with two y_ „ _porous cell §^ass tubes tightly fitted into it. One tube is closed for the Filtration of with a clip (fig. 43), and the other is attached to the Milk. pump. Place the porous cell in an outer vessel contain- ing milk. On exhau&ting the porous cell, a clear watery fluid slowly passes through. Test it for proteids and sugar. Notice the absence of fat and casein. 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 acid — test this (Lesson IX. 11) — having undergone XIII.] MILK, FLOUR, AND BKEAD. 9 1 the lactic acid fermentation, the lactose being split up by a micro-organism into lactic acid. 5. To Separate the 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 (casein and fat), and a clear fluid, the whey, which contains the lactose. Filter. (b.) By Rennet Ferment. — Take 5 cc. of fresh milk in a test- tube, heat it in a water-bath to 400 0., 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 neutra- lised 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 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 (b.), but boil the rennet first ; it no longer effects the change described above. The rennet ferment is destroyed by heat. (d.) 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. (e.) Take some oi the curd of 6 (a.). 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 ordinary Salts are present. (a.) Using the filtrate of 6 (a.), add magnesia mixture — Lesson XVII. 7, ({/.), i.e., ammonio-sulphate of magnesia, which gives a precipitate of pltosphates. {!>.) Silver nitrate gives a precipitate insoluble in nitric acid, indicating chlorides. 8. Boil milk in a porcelain capsule for a time to cause evapora- tion. It is not coagulated, but a pellicle of insoluble casein forms on the surface. Remove it and boil again ; another pellicle is formed. 92 PRACTICAL PHYSIOLOGY. [XIII. 9. Opacity of Milk — Vogel's Lactoscope. Apparatus required. — A graduated cylindrical cc. measure to hold 200 cc. ; a lactoscope, with parallel glass sides, 5 mm. apart (fig. 44) ; a burette or pipette, 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. ) Place 1 00 cc. of water in the cylindrical Fig. 44.- Lactoscope. measuring glass, and add 3 cc. of milk. Mix thoroughly. (c.) In a dark room place the lactoscope on a table, and 1 metre distant from it a lighted stearin candle. Fill the lactoscope with the diluted milk, and look at the candle-flame through the glass. If the contour of the flame can be seen distinctly, pour 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 Yogel gives the percentage of fat. 10. Wheat en Flour. (a.) Gluten. — Moisten some flour with water until it forms a tough 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 the insoluble albumenoids, some of the ash, and the fats. Draw out some of the gluten into threads, and observe its tenacious characters. (&.) Dry some of the gluten, and heat it strongly in a test- tube ; an ammoniacal odour similar to that of burned feathers is evolved. Water, which is alkaline (due to ammonia), condenses in the upper part of the tube. (c.) Extract 10 grams of wheaten flour with 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 third portion of (c.) for the biuret reaction. This is best seen on slightly heating. Take care not to boil the liquid, or the reaction for sugar will be got instead. (P Fig. 47— Deposit in :t Acid Fermentation " of Urine, a. Fungus; b. Amorphous sodium urate ; c. Uric acid ; d. Calcium oxalate. from the formation of lactic and acetic acids (although this is denied by some observers), then it gradually becomes neutral, and finally alkaline from putrefaction. It becomes lighter in colour, turbid, and a whitish heavy precipitate occurs ; a pellicle forms on the surface, it swarms with bacteria, and it has an ammoniacal odour, which is due to the splitting up of the urea, thus — CON2H4 + 2H.O = (NH4)2C03. The carbonate of ammonia makes the urine alkaline, and the earthy phosphates are precipitated because they are insoluble in an alkaline urine. The phosphate of lime is precipitated as such (amorphous), while the phosphate of magnesia unites with the 102 PRACTICAL PHYSIOLOGY. [XVI. ammonia and is precipitated as ammonio-magnesic phosphate or triple phosphate (MgNH4P04 + 6H20). Part of the ammonia escapes, and in addition to that united to the magnesic phos- phate, some unites with uric acid to form urate of ammonia. It is not known what ferment causes this reaction — whether mucus, bacteria-like organisms, or some amorphous ferment. N.B. — Although urine may be kept " sweet " for a long time in perfectly clean vessels, still when mixed with decomposing matter it has a marked tendency to putrefy. Insist that all urinary vessels be scrupulously clean ; and that all instruments 7 \^a»ft^\>®^^*^ ,'^-V^di-i;/,^/ %/ Fig. 48. — Deposit in Ammoniacal Urine (Alkaline Fermentation), a. Ammonio-mag- nesium phosphate ; d. Acid ammonium urate ; c. Bacterium urese. introduced into the bladder be properly purified by carbolic acid or other germicide. (a.) Place some normal urine aside for some days, preferably in a warm place. Observe 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. 47, 48). Fermentation is hastened 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. ADDITIONAL EXERCISE. 12. Estimation of the Acidity. — This is done by ascertaining the amount of caustic soda required to exactly neutralise 100 cc. of urine. As the soda solution cannot be prepared by weighing the soda because of the varying XVII. ] THE IXOltGANIC CONSTITUENTS OF UJEUNE. 103 amount of water contained in it, the soda solution must be titrated with a standard solution of oxalic acid. Make a normal solution of oxalic acid by dissolving 63 grams of dry cr3*stallised oxalic acid in ioco cc. water (CyELC^ + 2HoO=l26. i.e., half the quantity 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, 0=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 rosulic 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 9.2 cc. 0.8 cc. must be added to obtain a solution of which 1 cc. will correspond to 1 cc. of acid, so that for 1000 cc. of caustic soda 9.2 : 1000 : : 0.8 : x ( — = 84.2 ) V 9.2 ) 84. 2 cc. water must be added. (6.) Determine the Acidity of Urine. — Place 100 cc. of urine in a beaker, and add to it from a burette the normal soda solution (1 cc. = 0.063 oxalic acid). It is better, however, to dilute the soda solution to obtain a deci-normal solu- N tion (i.e., one-tenth as strong). In this case, 1 cc. = .0063 oxalic acid. 10 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. Suppose 15 cc. of the dilute (— | solution are used, then the acidity of ico cc. urine = Vio/ 15 x 0.0063 — °-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 = 1. 417 grams. The result is merely approximative. LESSON XVII THE INORGANIC CONSTITUENTS OP URINE. The constituents of the urine may be classified as follows : — (1.) Inorganic salts and water. (2.) Urea and relative bodies; uric acid, xanthin, guanin, kreatinin, allantoin, oxaiuric acid. (3.) Aromatic substances ; etber-sulpbo-acids of phenol, cresol, pyrocatechin, hippuric acid, Sec. (4.) Fattij non-nitrogenous bodies; oxalic, lactic, and glycerin- phosphoric acid. (5.) Pigments. (6.) Gases. The ratio of inorganic to organic constituents is 1 to 1.2 - 1.7. The amount of salts excreted in twenty-four hours is 1 6 to 24 grams (£ to f OS.). 1. Water is derived from the food and drink (normal quantity 1500 cc, or about 50 oz.). 104 PRACTICAL PHYSIOLOGY. [XVII. 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 grains), 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 AgN03 (1 pt. to 8 distilled water) = white, cheesy, or curdy precipitate in lumps insoluble in HN03. 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. Variations, increased in amount when the urine is secreted in excess, although the NaCl usually remains very constant (f per cent.) ; lessened in febzdle 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. (b.) Test urine from a case of pneumonia, and compare the amount of the precipitate with that of a normal urine. (c.) Evaporate a few drops of urine on a slide = octahedral or rhombic crystals, a compound of NaCl and urea. 3. Quantitative Estimation of Chlorides. — (1.) Standard Silver Nitrate. — Dissolve 29.075 grams fused silver nitrate in 1 000 cc. distilled water. 1 cc. = 0.01 NaCl. (2.) Saturated Solution of Neutral Potassic Chromate. {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 todr o 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 soda and potash. The total quantity of sulphuric acid, in twenty-four hours is 3 to 4 grams (45 to 60 grs. ). They have no clinical significance. Sulphuric acid, however, exists in urine not only in combination with alkalies, as indicated above, so-called " preformed sulphuric acid," but also with phenol, skatol, and other aromatic substances forming aro- matic ether-sulpho-com pounds, or ethereal hydrogen sulphates, the " combined sulphuric acid." The ratio of these two is about 1 of the former to . 1 of the latter. (a.) Test with a soluble salt of barium (the nitrate or chloride) = white heavy precipitate of barium sulphate, insoluble in HN03. 5. The Phosphates consist partly of alkaline and partly of earthy salts in the proportion of 2 to 1. The latter are insoluble XVII] THE INORGANIC CONSTITUENTS OF URINE. 105 in an alkaline medium, and are precipitated when the urine becomes alkaline. They are insoluble in water, but soluble in acids; in urine they are held in solution by free C02. The alkaline phosphates are very soluble in water, and they never form urinary deposits. 6. The Earthy Phosphates are phosphates of lime and mag- nesia. Quantity 1 to 1.5 grams (15 to 23 grs.). They are pre- cipitated when the urine is alkaline, although not in the form in which they occur in the urine (Lesson XVI. 11). They are iusoluble in water, readily soluble in acetic and carbonic acid, and are precipitated by ammonia. (a.) 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 increased 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, with perhaps traces of potassium phosphate ; they 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 potash, and heat gently until the phosphates 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.] (6.) To urine add about half its volume of nitric acid, and then add solution of ammonium molybdate and boil = a canary-yellow precipitate of ammonium phospho-molybdate. N.B. — The molyb- date is apt to decompose on keeping. (c.) To urine add half its volume of ammonia, and allow it to stand = a white precipitate of earthy phosphates. Filter and test the filtrate as in 7 (b.). (d.) It gives the reaction for phosphates. This method sepa- rates the alkaline from the earthy phosphates. (e.) To urine add half its volume of baryta mixture [Lesson XIX. 2 (c.)]=a copious white precipitate. Filter and test the filtrate as in 7 (c). It gives no reaction for phosphoric acid, showing that all the phosphates are precipitated. (/.) To urine add excess of ammonium chloride, and ammonia 106 PBA.CTICAL PHYSIOLOGY. [XVII. = a white precipitate of earthy phosphates and oxalate of lime. Filter, and to the filtrate add a solution of magnesic sulphate = a precipitate of the alkaline phosphates as triple phosphate. If the filtrate be tested for phosphoric acid by 7 (c), no precipitate will be found. (g.) Instead of 7 (/.), use magnesia mixture, composed of magnesic sulphate and ammonium chloride, each i part, distilled water 8 parts, and liquor animonise i part. It gives the same result as in 7 *(/• )• (h.) To urine acid 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(U203)]S[H4P04. This reaction forms the basis of the process for the volumetric estimation of the phosphoric acid. 7. 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. (a.) To a very dilute solution of uranium acetate add potassium ferrocyanide = a brown colour. 8. In some pathological urines the phosphates are deposited on boiling. (a.) Boil such a urine = a precipitate. It may be phosphates or albumin. An albuminous precipitate falls before the boiling- point is reached, and phosphates when 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 unchanged. 9. Microscopic Examination. — As the alkaline phosphates are all freely soluble in water, they do not occur as a urinary deposit. The earthy phosphates, however, may be deposited. (a.) Examine a preparation or a deposit of calcic phosphate, which may exist either in the amorphous form or the crystalline condition, when it is known as " stellar phosphate " (fig. 49). (b.) Prepare " stellar phosphate " crystals by adding some calcium chloride to normal urine, and then nearly neutralising. On standing, crystals exactly like the rare fig. ^.-steTar Phosphate, clinical form of stellar phosphate are ob- tained, (c.) Triple Phosphate or ammonio-magnesic phosphate never occurs in normal urine, and when it does occur, indicates the XVII.] THE INORGANIC CONSTITUENTS OF URINE. IO7 FIG. 50. — Various Forms of Triple Phosphate. decomposition of urea to give the ammonia necessary to combine with magnesic phosphate to form this compound. It forms large, clear "knife-rest" crystals (fig. 50). (d.) If ammonia be added to urine, the ammonio-magnesic phosphate is thrown down in a feathery form, which is very rarely met with in the investigation of human urine clinically (fig. 51). 10. General Rules for all Volu- metric Processes. (a.) The burette must be care- fully washed out with the titra- ting solution, and must be fixed vertically in a suitable holder. (6.) All air-bubbles must be re- moved from the burette as well as from the outflow tube. The latter must be quite filled with the titrating solution. (c.) Fill the burette with the solution up to zero, and always 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 thoroughly well mixed. 11. Volumetric Process for Phos- phoric Acid, with Ferrocyanide of Potassium as the Indicator. — 1 cc. of the SS. (Uranium acetate) = .005 gram of phosphoric acid. (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. (d.) Fill a Mohr's burette with the SS. of uranium acetate up to zero, or to any mark on the burette. See that the Mohr's clip is tight, and that the outflow tube is filled with the SS. Note the height of the fluid in the burette. Heat the urine Fig. ex. Feathery Forms of Triple Phosphate. io8 PRACTICAL PHYSIOLOGY. [XVII. solution in the beaker to about 8o° C. Drop in the SS. (u Stan- dard 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 this on a white plate. (e.) Boil the 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 solu- tion 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 phosphates in 50 cc. of urine ; as I cc. of SS. = .005 gram of phosphoric acid, then .005 x 17 = .085 gram of phosphoric acid in 50 cc. of urine. Suppose the patient passed 1250 cc. of urine in twenty-four hours, then lo : 12 w : : .08=; : x I-5° X — 5 = 2.12 grams of phosphoric 50 in twenty-four hours. 12. Solutions Required. Sodium Acetate Solution. -Dissolve 100 grams of sodium acetate in 100 cc. pure acetic acid, and dilute the mixture with dis- tilled water to 1000 cc. Potassium Ferro- cyanide Solution. — Dissolve 1 part of the salt in 20 parts of water. Uranium Acetate Solution (1 il / \ \mi mi FIG. 52.— Burette Meniscus. CC. = .005 gram'H3P04). Ertoann's Float. — Dissolve 20.3 grs. of pure uranium oxide in strong acetic acid; dilute with distilled water to a litre. The strength of this solution must be ascertained by means of a standard solution of sodium phosphate. Or dissolve 20.3 grams uranium nitrate in strong acetic acid, and dilute the solution to 1 litre. Apparatus Required. — Mohr's burette, fitted in a stand, and provided with a Mohr's clip; piece of white porcelain; tripod stand and wire-gauze ; small beaker ; two pipettes, one to deliver 50 cc, the other 5 cc. ; glass rod. 13. Reading off the Burette.— In the case of the burette being XVIII] ORGANIC CONSTITUENTS OF THE URINE. IO9 filled with a watery fluid, note that the upper surface of the water is concave. Always bring the eye to the level of the same horizontal plane as the bottom of the meniscus curve. Fig. 53 shows how different readings may be obtained if the eye is placed at different levels, A, B, C. 14. Erdmann's Float (fig. 53) consists of a glass vessel loaded with mercury, so that it will float vertically. It is used to facilitate the reading off of the burette. It has a horizontal 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 the ring on the float. 15. The Lime, Magnesia, Iron, and other inorganic urinary constituents are comparatively unimportant, and have no known clinical significance. LESSON XVIII. ORGANIC CONSTITUENTS OF THE URINE. 1. Urea (CON2H4) is the most important organic constituent in urine, and is the chief end-product of the oxidation of the nitrogenous constituent 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 an isomer of ammonium cyanate. It may be regarded as a diamid of C00 or as carbamid = CO ' fe „ 2 „ _ «*««««- w ^ ^ Urea represents the final stage of the metamorphosis of albu- minous substances within the body. More 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 baryta mixture — Lesson XIX. 2 (c.) — to precipitate the phosphates. Filter, evaporate the filtrate to dryness in an evaporating chamber, and extract the residue with boiling alcohol. Filter off the alcohol solution, place some of it on a slide, and allow the crystals of urea, usually long, fine, transparent needles, to separate out. Examine them micro- scopically (fig. 54, a). 3. Combinations. — Urea combines with acids, bases, and salts. Evaporate human urine to one-sixth its bulk, and divide the no PRACTICAL PHYSIOLOGY. [XVIII. residue into two portions, using one for the preparation of nitrate, and the other for oxalate of urea. 4. Urea Nitrate (CH4£T20, HN03). (a.) To the concentrated urine add strong pure nitric acid = a precipitate of glancing scales of urea nitrate, which, being almost insoluble in HN03, -separate out in rhombic plates or six-sided tables, with a mother-of-pearl lustre, and often imbri- cate arrangement. (b.) Examine the crystals microscopically (fig. 54). (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 Fig. 54.— a. Urea ; b. Hexagonal plates ; and c. Smaller scales, or rhombic plates of urea nitrate. of pure nitric acid on the free end of the thread. The acid will pass into the fluid, and microscopic crystals of urea nitrate will be formed on the thread. After a time examine the preparation microscopically. 5. Urea Oxalate (CH4N20)2 C2H204 + H20. (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. (6.) Examine them microscopically (fig. 55). (c.) Add oxalic acid to a concentrated solution of urea = a XYIIL] ORGANIC CONSTITUENTS OF THE URINE. II I precipitate 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, c), but substitute oxalic for the nitric acid. 6. Urea and Mercuric Nitrate (2CON2H4 + Hg(NOs), + 3HgO). (a.) To urine or urea solution 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. 7. Other Reactions of Urea. — Make a strong watery solution of urea, and with it perform the following tests : — (a.) Allow a drop to evaporate on a slide, and examine the crystals which form (fig. 54, a). (6.) Repeat, if you please, the exer- cises under Lesson XYIIL 4. (c.) To a strong solution of urea add pure nitric acid = a precipitate of urea nitrate (fig. 54, 6). (d.) To a strong solution of urea add ordinary nitric acid tinged yellow with nitrous acid, or add nitrous acid itself ; bubbles of gas are given off, consisting of carbon dioxide and nitrogen. (e.) Put some of the urea nitrate precipitate obtained in 4 (a.) into the test-tube A (fig. 56), and some lime-water in B. Add nitrous acid to A. Cork the tube. The pre- cipitate dissolves. C02 and N are given off, the COo makes the lime-water in B white. Fig. 55.— Crystals of Oxalate of Urea from Urine. Carbon Urea. Nitrous Acid. Dioxide. Nitrogen. CON2H, + 2(HNOs) = CO., + N4 + It Fig. 56. Water. 3H,0. (/.) Mercuric nitrate gives a greyish-white cheesy precipitate. (g.) Add caustic potash, and heat. The urea is decomposed and ammonia is evolved. 8. With Crystals of Urea perform the following experiments : — (a.) Biuret Reaction. — Heat a crystal in a hard tube; the crystal melts, ammonia is given off, and is recognised by its smell and its action on litmus, while a white sublimate of cvanuric acid is deposited on the upper cool part of the tube. Heat the tube until there is no longer an odour of ammonia. Allow the tube to cool, add a drop or two of water to dissolve the residue. 112 PRACTICAL PHYSIOLOGY. [XIX. a few drops of caustic soda or potash, and a little very dilute solution of cupric sulphate = a violet colour (biuret reaction). Two molecules of urea yield one of biuret. co{n§ _co<*=« +nh (b.) Place a large crystal of urea in a watch-glass, cover it with a saturated watery solution of furfurol, and at once add a drop of strong hydrochloric 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 per- formance. 9. Occurrence. — Urea" occurs in the blood, lymph, chyle, liver, lymph glands, spleen, lungs, brain, saliva, amniotic fluid. The chief seat of its forma- tion is very probably the liver. It also occurs in the urine of birds, reptiles, and mammalia, but it is most abundant in that of carnivora. 10. 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 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. Muscular exercise has little effect on the amount. (b.) In Disease. — In the acute stage of fevers and inflammations there is an increased formation and discharge, also in saccharine diabetes (from the large quantities of food consumed). It is diminished in anaemia, cholera, by the use of morphia, in acute and chronic Bright's disease. If it is retained within the body, it gives rise to uraemia, when it may be excreted by the skin, or be given off by the bowel. LESSON XIX. VOLUMETRIC ANALYSIS FOR UREA. 1. Before performing the volumetric analysis for urea, do the following reactions, which form the basis of this process : — (a.) 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. (c.) To urine add hypobromite of soda. At once the urea is decomposed, and bubbles of gas — N — are given off. XIX.] VOLUMETRIC ANALYSIS FOR UREA. I I 3 2. Liebig's Volumetric Process for Urea with Sodic Carbonate as the Indicator. — 1 cc. of the SS. (mercuric nitrate) = .01 gram or 10 milligrams of urea. (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. (c.) Mix 40 cc. of urine with 20 cc, i.e., half its volume, of a solution of barium nitrate and barium hydrate (composed of one volume of solution of barium nitrate and two volumes of barium hydrate, both saturated in the coldj. This precipitates the phos- phates, sulphates, and carbonates. (d.) Filter through a dry filter to get rid of the above salts. While filtration is going on, fill the burette with the standard solu- tion (SS.) of mercuric nitrate up to the mark 0 on the burette. See that there are no air-bubbles, and that the outflow tube is also filled. (e.) With a rnpette take 15 cc. of the clear filtrate and place it in a beaker. N.B. — This corresponds 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 background. (/) Note the height of the fluid in the burette. Run in the SS. of mercuric nitrate from the burette into the 15 cc. of the mixture, in small quantities at a time, until the precipitate ceases. Stir and mix thoroughly with a glass rod. After each addition, with the glass rod lift out a drop of the mixture and place it on one of the drops of sodic carbonate until a pale yellow colour is obtained. This indicates that all the urea has been pre- cipitated, and that there is an excess of mercuric nitrate. Read off the number of cc. of the SS. used. (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. — Suppose 27 cc. of the SS. were used, and the patient passed 1200 cc. of urine in twenty-four hours : then .25 x .01 —.25 gram urea iu IO cc. I ''OO X 2 K 10 : 1200 : : .25 : x . — * = 30 srama of urea in twenty-four hours. This method yields approximately 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. 3. Correction for Sodic Chloride. —Two cc. were deducted in the above process. Why ? On adding mercuric nitrate to a H 114 PRACTICAL PHYSIOLOGY. [XIX. solution containing sodic chloride, the mercuric nitrate is decom- posed and mercuric chloride formed, and as long as any sodic chloride is present, there is no free mercuric nitrate to combine with the urea. Proofs of this : — (a.) To a solution of sodic chloride (normal saline) add mercuric nitrate = precipitate. (b.) To a solution of sodic chloride (normal saline) add a few crystals of urea, then add mercuric nitrate. At first there is no precipitate, or, if there is, it is redissolved ; but by-and-by a white precipitate is obtained. (c.) To a solution of urea (acid) add mercuric chloride = no precipitate. 4. Solutions Required. Baryta Mixture. — Prepared as in Lesson XIX. 2 (c). Mercuric Nitrate Solution. — (i cc. = .oi gram urea). Dissolve with the aid of gentle heat 77.2 grams of pure dry oxide of mer- cury in as small a quantity as possible of HN03, evaporate to a syrup, and then dilute with water to 1 litre. A few drops of HN03 will dissolve any of the basic salt left undissolved. N.B. — The exact strength of this solution must be estimated by titrat- ing it with a standard 2 per cent, solution of urea. Sodic Carbonate Solution. — 20 grains to the ounce of water. 5. Apparatus Required. — Burette fixed in a stand, funnels, beakers, filter-paper, glass rod, plate of glass, and three pipettes, 10, 15, and 20 cc. 6. Estimation of Urea by the Hypobromite Method. The principle of this method depends on the fact that urea is decomposed by alkaline solution of sodic hypobromite. The urea yields C02 (which is absorbed by the caustic soda), and N, which is disengaged in bubbles and collected in a suitable apparatus. Sodic Carbon Sodic Urea. Hypobromite. Dioxide. Nitrogen. Water. Bromide. CON2H4 .+ 3NaBrO = C02 + N2 + 2H20 + 3NaBr Every o. 1 gram of urea contains .04666 gram N; this at the ordinary temperature and pressure = 37.3 cc. of nitrogen; the calculation, therefore, is simple. In practice only 35.43 cc. are obtained, i.e., 8 per cent, less than the total N, but kreatinin, urates, and some of the other nitrogenous bodies present in the urine, compensate for this loss, so that the original number is sufficient for all practical 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 UKEA. I I 5 (a.) Study these forms of apparatus, but make the experiment with the apparatus of Dupre or Steele. 7. Dupre^s Apparatus. — In this apparatus the graduation on the collecting tube represents the percentage of urea, and not cc. of N. The collecting tube, which is clamped above, is placed in a tall vessel containing 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. (6.) With a pipette measure off 5 cc. of the clear filtered urine, and place it in the short test-tube. With a pair of forceps care- fully introduce the tube with the urine into the flask, and place the caoutchouc stopper in the latter. (c.) Test to see if all the connections are tight. Open the clamp at the 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. Close the clamp, and raise the collecting tube. If the apparatus be tight, no air will pass in, and on lowering the collecting tube the water will stand at zero inside and outside the tube. (d.) Mix the urine gradually with the hypobromite solution by gently tilting over the flask, and ultimately move the flask so as to wash out the test-tube with the hypobromite solution. Gas is rapidly given off, the C02 is absorbed by the caustic soda, while 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 slightly lower the measuring tube. After all effervescence has ceased, and when the N collected in the collecting tube has cooled to the temperature of the room— i.e., in three to five minutes — raise the collecting tube until the fluid inside and outside stands at the same level. Read off the gra- duated tube j this gives the percentage of urea. It is to be remembered that other bodies in the urine, such as uric acid (urates) and kreatinin — but not hippuric acid — also yield nitrogen by this process; further, that only about 92 per cent, of the N of the urea is given off in the above processes. These sources of fallacy are, however, taken into account in graduating the apparatus. 8. Steele's Apparatus (fig. 57). — This is practically the same apparatus, but a graduated burette is substituted for the gradu- ated collecting tube. (a.) Use this apparatus in a similar manner. (/>.) Read off the number of cc. of X evolved, and from this cal- culate the amount of urea. Every 37.3 cc. X n6 PRACTICAL PHYSIOLOGY. [XIX. 9. Solutions Required. (A.) For Dupre's Apparatus. Hypobromite Solution. — Dissolve 5 cc. of bromine in 45 cc. of a 40 per cent, solution [( li. of caustic soda. N.B. — This solution does not keep, and must be freshly prepared. (B.) For Steele's Apparatus. Hypobromite Solu- tion.— Twenty grams of caustic soda are dis- solved in water, and the solution is diluted to 250 cc. ; after cooling, add 5 cc. of bromine, and mix. Keep in a stoppered bottle in the dark ; as it soon decom- poses, it should be made fresh. 10. Study also Char- teris's apparatus. The bromin e and caustic soda are mixed in a marked measure, so that the Fig. 57.— Steele's Apparatus for Urea. A. Frask for hypobromite is always hypobromite ; B. Tube for urine ; C. Burette ; D. f resn while the collect- Vessel with water : E. Vessel with water to cool A. ing tube for the N is so graduated as to indicate a certain percentage of urea. 11. Study Squibb's apparatus.. In all these cases directions are supplied with the apparatus. ADDITIONAL EXERCISES. 12. Hiifner's Apparatus (fig. 58). — It consists of a stout fusiform glass cylinder (B) (capacity 100 cc), connected below by means of a glass tap with a smaller tube (capacity 5 cc. ). The capacity of A is important, as it contains the urine, so that it must be previously calibrated. The remainder of the apparatus consists of a glass bowl (C) fitted by means of a caoutchouc stopper upon the upper 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 XIX VOLUMETRIC ANALYSIS FOR UREA. 117 wash every trace of urine out of B. Place C in position, fill B with a freshly- prepared 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, avoid- in" the presence of air- bubbles. Insert D over B. Open the tap when the FIG. 58.— Hiifner's Urea Apparatus. hypobromite mixes with the urine and the gases are evolved. The quantity of urea is calculated from the volume of N evolved. 13. Gerrard's Apparatus (fig. 59). Method of Using. — Pour into the tube 5 cc. of the urine to be examined, and in the bottle (a) 25 cc. or 6 fluid drachms of sodium hypobromite solution. Place the tube carefully inside the bottle, as shown in the illustration, avoid- n8 PRACTICAL PHYSIOLOGY. [XIX. ing spilling any of the contents. Fill the glass tubes {b, c) with water, so that the level reaches the zero-line, taking care that when this is done the tube (c) contains only a little water by being placed high — it having to receive what is displaced from (c) by the nitrogen evolved. Now connect the india-rubber tubing to the bottle, and noting lastly that the water is exactly at zero, upset the contents of the tube into the hypobromite solution. Nitrogen is evolved, and depresses the water in (b). When this ceases, lower (c) until the level of the water in both tubes are equal. To be exact, dip (a) into cold water to cool the gas before taking a reading, and note the results, which shows per- centage of urea. The solution of hypobromite of soda is made by dissolving ioo grams of caustic soda in 250 cc. of water, then adding 22 cc. of bromine. To avoid the danger of the bromine vapour, the bromine is sold in hermeti- Fig. 59. — Gerrard's Urea Apparatus, as made by Gibbs, Cuxson, & Co., Wednesbury. Fig. 60. -Ureameter of Doremus with Pipette. cally sealed glass tubes, containing 2.2 cc. ; one of these placed in the large bottle with 25 cc. of the soda solution gives, when broken with a sharp shake, the exact quantity of hypobromite for one estimation of urea, and all bad odour is avoided. 14. Ureameter of Doremus (fig. 60). — 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 ureameter, as far as the bend, and the nipple is compressed slowly. The urine will then rise through the hypobromite solu- tion, and the gas evolved will collect in the upper part of the tube. Each division indicates .001 gram of urea in 1 cc. of urine. The percentage XX.] URIC ACID, ETC. II9 of urea present in the urine is found by simply multiplying the result of the test by 100. 15. Synthetic Preparation of Urea. — Heat coarsely - powdered ferro- cyanide of potassium (FtCv^KCy-f 3H0O, 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 up show no trace of yellow. If it be over-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 chloride. Cool and extract with cold water, and add to the solution dry ammonium sulphate to the extent of three-fourths of the weight of potassic ferrocyanide used. Filter, evaporate in a water- bath at about 6o°-7o° C. (at which temperature ammonium cyanate passes into urea). At first potassic sulphate crystallises out ; remove it from time to time. Lastly, evaporate 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 (Pfliiger and Bohland's Approximative Method). — (i.) Take ten 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 O.04 gives the total N. (ii.) KjeldahVs Method. — This method, when once the standardised solutions are prepared, and the apparatus set up, can be carried out in about an hour, but several estimations can be carried out simultaneously. In this 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 sulphuric acid. The ammonia is calculated by titrating the sulphuric acid with standard caustic soda. (See Sutton's Volumetric Analysis. p. 68, 5th edit., 1886.) LESSON XX. URIC ACID— URATES— HIPPURIC ACID- KREATININ, &c. 1. Uric Acid (C-HjNjOg) contains 35.33 per cent, of N, and, next to urea, is the constituent of the urine whereby the largest quantity of N of the body is excreted, whilst in birds, reptiles, and insects it forms the chief nitrogenous excretion. The pro- portion of urea to uric acid is 45 : 1. The following structural formula show its relation to urea, and the results of its decomposition : — XH — CO I I CO C — NH I II > CO XH C — NH 120 PRACTICAL PHYSIOLOGY. [XX. 2. Quantity. — 0.5 gram (7-10 grs.) daily. It is dibasic, colourless, and crystallises, chiefly in rhombic plates, and when the obtuse angles are rounded the "whetstone" form is obtained. It often crystallises spontaneously in rosettes from saccharine diabetic urine. It is tasteless, reddens litmus, and is very insoluble in water (18,000 parts of cold and 15,000 of warm water), insoluble in alcohol and ether. In the urine it occurs chiefly in the form of acid urates of soda (C5H0N4O3, HNa) and potash. (a.) In a conical glass, add 5 parts of HC1 to 20 parts of urine, put it in a cool place, and allow it to stand for twenty-four hours. Yellow or brownish- coloured crystals of uric acid are deposited FIG. 61.— Uric Acid. a. Rhombic tables (whetstone form); b. Barrel form ; [c. Sheaves; d. Rosettes of whetstone crystals. 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. (b. ) 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 prisms, &c. They are yellowish 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. 61, 62). (a) The crystals are soluble in caustic soda or potash. Observe this under the microscope. XX. URIC ACID, ETC. 121 (d.) 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 some uric acid in a porcelain capsule, add nitric- acid, and heat gently, taking care that the temperature is not too high — not above 40° C. Very disagreeable fumes are given off, while a yellow or reddish stain re- mains. 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 murexide, CgH8(NH4)N506, appears. It turns violet on adding caustic potash. (b.) Kepeat the experiment, but act on the residue with caustic soda or potash, when a violet-blue colour — discharged by heat — is obtained. The latter distinguishes it from guanin. When uric acid is acted on by nitric acid, alloxantin (CsH4N40:) is formed, which, on being further heated, yields alloxan (C4Hs^T204) ; the latter strikes a purple colour — murexide — with ammonia. (c.) Place some uric acid on a microscopic slide, and dissolve it in liquor potassfe. Heat, if necessary ; add hydrochloric or nitric acid just to excess, and examine with the microscope the crystals of uric acid which form. They may be transparent rhombs with obtuse angles, dumb-Dells, or in rosettes. (d.) Dissolve some 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.) SchifFs Test. — Dissolve some uric acid in a small quantity of sodic carbonate. Place, by means of a glass rod, a drop of solution of silver nitrate on filter-paper, and on this place a drop .Fig. 62.— Uric Acid. a. Khomboidal, truncated, hexahedral, and laminated crystals ; b. Rhom- bic 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. 122 PRACTICAL PHYSIOLOGY. [XX. of the uric acid solution. A dark brown or black spot of reduced silver appears. (/.) Garrod's Microscopic Test. — Add 6 to 8 drops of glacial acetic acid to 5 cc. urine in a watch-glass, put into it a few silk threads, and allow the whole to stand for twenty-four hours, taking care to prevent evaporation by covering it with another watch-glass or small beaker. Examine the threads microscopi- cally for the characteristic crystals of uric acid, which are soluble in K.HO. A similar reaction may be done on a microscopic slide. (y.) Heat some uric acid in a test-tube. It blackens and gives off the smell of burnt feathers. 4. Uric Acid Salts (Urates). — Uric acid forms salts (chiefly acid), with various bases, which are soluble with difficulty in cold, but readily soluble in warm water. HC1 and acetic acid decom- pose urates, and then the uric acid crystallises. Urates form one of the commonest and least important deposits in urine. There is usually a copious precipitate, varying in colour frum a light pink or brick-red to purple. They occur in catarrhal affections 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. Ui'ates constitute the " lateritious " deposit or "critical" deposit of the older writers. Urates frequently 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 formulas of the more common urates : — Acid sodic urate ..... C5H3N403Na. Neutral sodic urate .... C5H2N403Na2. Acid ammonium urate .... CsHg^C^NELi). Acid potassic urate .... C5H3N4O3K. 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. Their occurrence is favoured by an acid reaction, a concentrated condi- tion 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. — Secure a specimen of " urates " 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. XX.] URIC ACID, ETC. I 23 (b.) Place some in a test-tube. Heat gently the upper stratum. It becomes clear, and on heating the whole mass of fluid, it also 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. (d.) Examine the deposit microscopically. The urates are usually ''amorphous," but the urate of soda may occur in the form of small spheres covered with spines, and the ammonium urate, of spherules often united together (fig. 48, d). (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 (fig. 63). (/. ) The same result as in (e) is obtained by dissolving the ordinary deposit of urates with caustic soda, and allowing some of it to evaporate on a slide. 6. Uric Acid from Serpent's Excrement.— Heat the powdered excrement in a porcelain yIG g _Tjrate of Soda vessel with 15-20 vols, of water just to boiling, add carefully small quantities of caustic potash or soda until the whole is dis- solved and there is no further odour of ammonia given off. Filter, and saturate the filtrate with C02, which causes at first a gelatinous and then a finely- granular precipitate 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, C9H(JN03 (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, chiefly in the form of alkaline hippurates (sodic hippurate). It belongs to the aromatic series. It dissolves readily in hot alcohol, but is sparingly soluble in water. Quantity in man .5 to 1 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), ami is excreted as hippuric acid in the urine. Benzoic Acid. Glycocoll. Hippuric Acid. Water. C7HG02 + CoHsXOo = C9H9X03 + H20. The amount is increased by eating pears, apples with their skins, cranberries, and plums. Nothing is known of its clinical significance. It seems to be formed chiefly from the husks or cuticular structures. 124 PRACTICAL PHYSIOLOGY. [XX. 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. 64). (c.) Boil with HNOg, and heat to dryness = odour of nitro- benzene a similar reaction Benzoic acid gives FlQ. 64.— Hippuric Acid. 8. Preparation of Hip- puric Acid. — (a.) Take 100 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 blot- ting-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. (6.) Boil horse's urine with milk of lime = a copious precipitate. Filter off the bulk of the precipitate 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. 9. Kreatinin (04H7N30) is a derivative of 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 — kreatinin. 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 5 the kreatinin -zinc-chloride is used as a microscopic test for its presence. It rarely occurs as a deposit, and nothing is known of its clinical significance. 10. Preparation of Kreatinin.— (a. ) 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 chloride, and set the vessel aside. After a time kreatinin- zinc-chloride is deposited on the sides of the vessel. (b.) To half a litre of urine add baryta-mixture (p. 113) until no further precipitation 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 XX.] URIC ACID, ETC. 12 twenty-four hours in the cold, whereby the salts are separated, filter, and t<> 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 warm water, and decompose 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, evaporate to dryness, and extract the kreatin from the residue with alcohol in the cold. A small quantity of kreatin remains un- dissolved. 11. Tests and Reactions, (a.) Examine the deposit microscopically, brownish balls, with radiating lines (fig. 65). It forms round +5 Fig. 65. Kreatinin-anc-cMoride. a. Balls with radiating marks ; b. Crystallised from water ; c. Barer forms from an alcoholic extract. (b.) Weyl's Test. — To urine add a very dilute solution of sodic nitro-prusside, and very cautiously caustic soda = a ruby-red colour, which is evanescent, passing into a straw colour. 12. Colouring-Matters of the Urine. — Several colouring-matters which give characteristic spectra seem to be present in the urine, including : — (1.) Urobilin, which occurs especially in the high-coloured urines of fever. It gives urine its red or reddish-yellow colour, and on the addition of ammonia it becomes yellow. (2.) Uro-Chrome is a yellow pigment. When a watery solution is exposed to the air it oxidises, and becomes red owing to the formation of uro-erytlnin. 126 PKACTICAL PHYSIOLOGY. [XX. (3.) Indigo-forming Substance (Indican). — This is derived from indol, CgH^N, which is developed in the intestinal canal from the pancreatic digestion of proteids, and also from the putrefaction of albuminous bodies. It may also be formed 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 in doxyl- sulphate of potassium (OsH6NS04K). 13. General Reactions for Urine Pigments. (a.) Add to normal urine a quarter of its volume of HC1, and boil = a fine pink or yellow colour. (b.) Add nitric acid = a yellowish-red colour, usually deeper than the original colour. (c.) 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, sulphate, and phosphate of lead. Filter ; the filtrate is an almost colourless solution. This substance is used to decolorise urine for the sa.c- charimeter. (e. ) Filter urine through animal charcoal ; the urine will be decolorised. (/.) If possible, obtain a dark-yellow coloured urine, and per- form the following test : — Take 40 drops of urine + 3 to 4 cc. of strong HC1 and 2 to 3 drops of HN03 ; on heating, 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 HC1, add, drop by drop, a saturated solution of chloride of lime (i.e., bleaching- powder, which also contains hypochlorite of calcium) = a blue colour. Shake up with chloroform and the blue colour is absorbed by the latter. 14. Phenol (carbolic acid), CgHgO, occurs in the urine as phenol-sulphonate of potassium, C6H50 - SOo OK. There is a corresponding salt of Cresol, most abundant in the 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 (CgHoBrsOH). (b.) Neutralise and add neutral ferric chloride = violet colour. (c.) Heated with Millon's reagent it gives a red colour. (See also p. 79.) The pathological pigments — bile, blood, &c. — occurring in urine will be referred to later. 15. Mucus. — A trace of mucus occurs normally in urine. Col- lect fresh urine in a tall vessel, and allow it to stand for some XX] URIC ACID, ETC. 12/ time, when tine clouds (;i mucous clouds") like delicate cotton- wool appear. These consist of mucus entangling 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. Ferments 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 fer- ment, and on placing it in .2 per cent. HC1 at 400 C, the pepsin is dissolved and peptones are formed. Test for the peptones by the biuret reaction. ADDITIONAL EXERCISES. 17. Reactions of Normal Urine towards Reagents. (I.) Add 5 cc. of HC1 to 100 of urine. After twenty-four hours crystals of uric acid separate out. (2.) Add caustic soda or ammonia = precipitate 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 colouration due to urates. (4.) Add mercuric nitrate = white cloudiness, which disappears on shaking. This is a precipitate due to the formation of sodic nitrate and mercuric chloride (Hg(N03)2 + 2NaCl=2NaN03 + HgCl2), soluble in acid urine. After all the NaCl is decomposed — but not until then — a permanent precipitate, a com- pound of urea arid the mercury salt, forms. (5.) Silver nitrate = white precipitate of AgCl and Ag3P04 ; the latter falls first, and afterwards all the silver combines with the chlorine. The pre- cipitate is insoluble in HN03 but soluble in M + 4HO. (6.) Baric chloride = white precipitate of BaS04 and Ba3(P04)1.. (7.) Lead acetate = whitish precipitate of PbS04, PhCl-j, Pb3(P04U, and the pigments. (8.) Ferric chloride after acidulation with acetic acid = precipitate of Feo(P04)2. (9.) An ammoniacal solution of cupric oxide is decomposed and decolorised at the boiling-point by the urates. (10.) Tannic acid = no precipitate {Krukcnberg). 18. Estimation of Uric Acid. — This is sometimes done by the method (2, a), but it is not accurate. Haycraft's method depends on the formation of urate of silver, which is practically insoluble in water or acetic acid [British Medical Journal, 1SS5). The urate of silver is of a slimy nature and must be washed on an asbestos filter. The titration of the silver compound is by means of Volhard's amnionic thio-cyanate method (Sutton's Volumetric Analysis, 5th edit., 18S6, pp. 116, 324). 128 PRACTICAL PHYSIOLOGY. [XXI. 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. Inorganic 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 II.09 O.26 0.2I — Parlces. 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.g., sugar; and in the urine of a certain percentage of persons apparently enjoying perfect health, minute traces of albumin are sometimes present. When, however, these substances occur in considerable 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 consider- able 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. Various forms of proteid bodies may occur in the urine. The chief one is serum albumin ; but, in addition, serum-globulin, hemi-albumose, peptone, acid-albumin, and fibrin may be found. 2. Tests. — The demonstrator will procure an albuminous urine. With it perform the following tests. In every case the urine must be clear before testing, which can be secured by care- ful nitration. (a.) Coagulation by Heat. — Place 10 cc. 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 a large amount, a distinct coagulum. On standing, the coagulum is deposited. Precautions. — (i.) Always test the reaction of the urine, for albumin is only precipitated by boiling in a neutral or acid medium. Hence if the urine be XXL] ABNORMAL CONSTITUENTS OF THE URINE. 1 29 alkaline, boiling will not precipitate any albumin that may be present, (ii.) Boil the upper stratum of the fluid 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 the CO^, also precipitates earthy phosphates if they are present in large amount, hence a turbidity on boiling is not sufficient proof of the presence of albumin. The points of distinction are, that albumin goes down before the boiling-point is reached (coagulated at 750 C.), while phosphates are precipitated at the boiling-point. Again, the phosphatic deposit is soluble in an acid — e.g., acetic or nitric — while the albuminous coagulum is insoluble in these fluids. Some, therefore, advise that the test be done in the following manner : — (b.) Acidulate the urine with a few drops of dilute acetic or nitric acid, and then boil. If nitric acid be used, add one-tenth to one-twentieth of the volume of urine. Precautions. — If the urine contain only very minute traces of albumin, the latter may not be precipitated 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 part of the basic phosphates are changed into acid phosphates, and the albumin remains in solution as an albuminate (a com- pound of the albumin with the base). On heating the urine of a person who is taking copaiba, a deposit may be obtained, but its solubility in alcohol at once distinguishes it from coagulated albumin. This test acts with serum- albumin and globulin, and if the deposit occurs only after cooling, also with albumose, but not with peptone. (e.) Acidulate 10 cc. of urine with acetic acid, add one- fifth of its bulk of a saturated solution of magnesic or sodic sulphate, and boil = a precipitate. (d.) 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 crystalline deposit of urea 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. (e.) Acetic Acid and Potassium Ferrocyanide. — Acidify strongly with acetic acid, and add a solution of potassium ferro- cyanide = a white precipitate, 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 potassic ferrocyanide, and pour this over some urine in a test-tube by the contact method {.) 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. (c.) Urine containing pus gives the reactions for albumin, while, if mucus alone be present, it gives only those for mucin. 140 PEACTICAL PHYSIOLOGY. [XXIV. UNORGANISED DEPOSITS. A. In Acid Urine. i. 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. (6.) Tribasic 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. (b.) Oxalate of Lime. — Octahedral crystals, insoluble in acetic acid (fig. 70). (c.) Cystin (veryrare). — Hexagonal crystals, soluble in NH^HO (fig. 72). (d.) Leucin and Tyrosin (very rare). (Fig. 73.) {e.) Cholesterin (very rare). (Fig. 40.) 3. Urinary Calculi. B. In Alkaline Urine. I. Amorphous. {a.) Tribasic Phosphate of Lime dissolves in acids without efferves- cence. {b.) Carbonate of Lime. (See (c.) below.) 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 spines, and also amorphous granules (% 71). (c.) Carbonate of Lime. — Small colourless balls, often joined to each other ; effervescence on adding acids (microscope). {d.) Crystalline Phosphate of Lime. (e.) Leucin and Tyrosin (veryrare). (Fig. 73-) They are composed of urinary constituents which form urinary deposits, and may consist of one substance or of several, which are usually deposited FIG. 70. — Oxalate of Lime. Octa- hedra and Hour-glass forms. FlG. 71. — Acid Urate of Ammonium. in 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 XXIV.] UIUXARY DEPOSITS, ETC. I4I portion of blood-clot, or some albuminoid matter — in which crystals of oxalate of lime or globular urates become entangled. Layer after layer is then de- posited. In certain cases the nucleus may consist of a foreign body introduced from without. Calculi are sometimes classified as primary and secondary ; the former are due to some general alteration in the composition of the urine, whilst the latter are due to ammonia- cal decomposition of the urine, resulting in the precipitation of phosphates on stones already formed. This of course has an important bear- ing on the treatment 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 in- soluble in very acid urine. A higldy alkaline urine favours the formation of calculi, consist- ing of cede ium phosphate or triple phosphate, as these substances are insoluble in alkaline urine. Fig. 72.— 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. (b.) Scrape off a little, and heat it to redness on platinum foil over a Bunsen-burner. FIG. 73.— a. a. Leucin balls ; b b. Tyrosin sheaves ; c. Double balls of ammonium urate. (A.) If it be entirely combustible, or almost so, it may consist of uric acid or urate of ammonia, xanthin, cystin, coagulated hbrin or blood, or ureostealith. 142 PRACTICAL PHYSIOLOGY. [XXIV. (B.) If incombustible, or if it leaves much 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 ammonia give the murexide 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 gravel. When retained in the bladder, they are usually spheroidal, elliptical, and some- what flattened; are tolerably hard-; the surface may be smooth or studded with fine tubercules ; the colour may be yellowish, reddish, or reddish-brown, very rarely white. When 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 relations : 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, which 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. .73). The other calculi of this group are very rare. 6. (A.) Group. — Apply the Murexide Test. It is J Treat the original powder with ) No odour = Uric acid. obtained ( potash. ) Odour of NH.3 = Ammonium urate. The residue is not coloured, but becomes yellowish-red ) _ ^ ,j . on adding caustic potash . . . . . ) ~ The residue is not coloured either by KHO or NH4HO ; ) the original substance is soluble in ammonia, and > = Cystin. 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 HNO3 . . . . ) XXIV.] URINARY DEPOSITS, ETC. 1 43 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 warty; 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 HC1, it effervesces (CO.,). Oxalate of lime is not dissolved by acetic acid. (iii.) Carbonate of Lime. — Bare in man ; when met with, they usually occur in large numbers. Dissolve with effervescence in HC1. 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 urea. 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 lime is in excess, they are harder. A whitish 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.) The substance gives the murexide reaction, indicates urates. The residue is treated with water. It is soluble, and ( Neutralise ; add platinic chloride, a yel- ) _ p , the solution is] low precipitate } -fotash. alkaline . . ( The residue yields a yellow flame . . = Sodium. f Ammonium oxalate gives a white crys- talline precipitate .... Ammonium oxalate gives no precipitate, but on adding ammonium chloride, sodic phosphate, and ammonia, there V = Magnesium. is a crystalline precipitate of triple- phosphate ...... Scarcely soluble ; the solution is scarcely alka- line ; soluble in acetic acid Calcium. 144 PRACTICAL PHYSIOLOGY. [XXIV. (ii.) The original substance does not give the murexide test. Treat the original substance with hydrochloric acid. It dissolves with effervescence I It dissolves with effervescence It dissolves without ef- fervescence. Heat the original sub- stance, and treat it with HC1 . There is no effervs'ce. Heat in a capsule V fit melts.\ The origi- I nal stone V treated I withKHOJ It does not melt on heatinsr . E v o 1 v NH3. Evolves NH3. Calcic carbonate. Magnesic carbonate. = Calcic oxalate. = Triple phosphate. = Neut. calc. phosp. = Acid calc. phosp. 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 ?). (v.) Heat. (a.) If a turbid urine becomes clear = urates. (b.) If it becomes turbid — earthy phosphates or albumin. Albumin is precipitated before the boiling-point is reached (70° C), whilst phosphates are thrown down about the boiling-point. It is necessary, however, to add HN03, which will 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 HN03 (albumin). Estimate approxi- mately the amount of albumin present. (vi.) Test for Chlorides, with HN03 and AgN03 (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. (viii.) Make naked-eye, microscopic, and chemical examinations of the sediment. XXIV.] URINARY DEPOSITS, ETC. 1 45 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. Suppose the solution contains one or more of the following — blood, bile, urea, uric acid, or ferments — proceed as follows : — (a.) If blood is suspected, use the spectroscope if the colour appears to indicate the presence of blood. (6.) If the colour is such as to suggest the presence of bile, concentrate the fluid on a water-bath, and apply Gmelin's test for the bile-pigments (Lesson XI. 6). If proteids are absent, apply Pettenkofer's test for the bile-acids (Lesson XL 3). If proteids are present, proceed as in Lesson IV. 3, B. ). (c.) In testing for urea, proceed as in Lesson IV. 3, F., by pre- cipitating with baryta mixture. Filter, evaporate the filtrate to dryness, redissolve the residue with absolute alcohol, and allow some of the alcoholic extract to evaporate on a slide, and use the microscope for the detection of crystals of urea. Apply the other reactions for urea in Lesson XVIII. 4 and 7. (d.) For uric acid or its salts, add hydrochloric acid to pre- cipitate the uric acid in crystals — Lesson XX. 2, (a) — and to the latter apply the murexide test. (e.) If ferments are suspected, their action must be tested on fibrin or starch mucilage, as the case may be, the reaction of the fluid being adapted to the ferment tested for. B. If a Powder or Solid Substance be given to you — (a.) Examine it with the naked eye and microscopically, whether it be amorphous or crystalline. (b.) Burn some in a tube; smell it to detect any odour. Observe if it leaves an ash. (c.) Examine its solubility in water, caustic soda, salt solutions, alcohol, and ether. (d.) Apply tests in Lesson I. 1, for p>foteids. (e.) If it contain a proteid, test its solubility in water. Native albumins, peptones, and gelatin are soluble; the others are insoluble. Confirm by other tests in Lesson I. (/.) If it be not a proteid (or if proteids be present, remove them), test if it be soluble in cold water, and to the solution apply the tests for dextrin and glycogen (Lesson III. 4, 7), reducing sugars, e.g., grape or milk sugars (Lesson III. 8). The former, in a concentrated solution, is precipitated by absolute alcohol, the latter is not. If cane-sugar be suspected, invert it (Lesson K 146 PRACTICAL PHYSIOLOGY. [XXIV. XI Y. g\ and test for a reduciDg sugar. Test also for urea (Lesson XVIII. 4, 7). (g.) Ascertain its solubility in warm water, starch (Lesson II. I. 1), urates (Lesson XX. 5), tyrosin (Lesson X. 5). (h.) Test for uric acid (Lesson XX. 3). (i.) Cholesterin is insoluble in cold water and alcohol, but soluble in ether. On evaporation of the ether, the characteristic crystals are obtained (Lesson XI. 7). (j.) Fats melt on heating, and are soluble in ether, leaving a greasy stain (Lesson IV.). C. Analysis of Urine. — The student must also practise the analysis of urines containing one or more abnormal constituents, and he must also 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 him- self in the methods in common use. PART II.— EXPERIMENTAL PHYSIOLOGY. Instruments, &c, to be provided by each Student. — Before begin- ning the experimental part of the course, each student must provide himself with the following : — A large and a small pair of scissors ; a large and a fine pointed pair of forceps ; a scalpel ; a blunt needle or "seeker" in a handle ; pins; fine silk thread ; bees' -wax; sealing '-wax ; two cameVs-hair brushes of medium size. It is convenient to have them all arranged in a small case. PHYSIOLOGY OF MUSCLE AND NERVE. LESSON XXV. GALVANIC BATTERIES AND GALVANOSCOPE. Ujulx^ 1. Daniell's Cell consists of a glazed earthenware pot with a handle (fig. 74), and containing a saturated solution of cupric sulphate. Some crystals of cupric sulphate are placed in it to keep the solution saturated. The pot itself is about 18 cm. high, and 9 cm. in diameter. In the copper solution is placed a roll of sheet-copper, provided with a tongue, to which a binding screw is attached. Within is a porous unglazed cylindrical cell contain- ing 10 per cent, solution of sulphuric acid. A well amalgamated rod of zinc, provided at its free end with a binding screw, is im- mersed in the acid. The zinc is the negative ( - ), and the copper the positive ( + ) pole. 147 Fig > ■■■ ; — ~~. ' 74.— Daniell's Cell. 148 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 10 per cent, 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 + £^> £^J — 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. (6.) The following is another con- venient " Amalgamation Mixture " : — With the aid of gentle heat dissolve 4 parts 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 using a battery the zincs must be washed and dried, the porous cells must be carefully washed, and com- pletely immersed in a large quantity of water, frequently renewed. Fig. 75. — Large Grove's Element. 4. Grove's Cell (fig. 75) consists of an outer glazed earthenware, glass, or ebonite vessel, containing a roll of amalgamated zinc and dilute (10 per cent.) sulphuric acid. In the inner porous cell is placed platinum foil with strong nitric acid. The platinum and zinc are provided with binding screws. The platinum is the + positive pole or anode, the zinc the - negative pole 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 XXV.] GALVANIC BATTERIES AND GALVANOSCOPE. 149 use the battery ought to be placed in a draught chamber to pre- vent the nitrous fumes from affecting the experimenter. 5. Bichromate Cell (fig. 76). — This consists of a glass bottle containing one zinc and two carbon plates immersed in the following mixture: — Dissolve 1 part of potassic bichromate in 8 parts of water, and add 1 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 intensity. Other forms of batteries are used, but the foregoing are sufficient for the purposes of these exercises. 6. 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. The existence of this elec- trical current may be proved in main- ways, e.g., by the effect of the current on a magnetic needle. (b.) Use a vertical galvanoscope, or, as it is called by telegraphists, a detector (fig. 77), in which the magnetic needle is so loaded as to rest in a vertical position. A needle attached to this moves over a semicircle graduated into degrees. Con- Fig. 76.— Bichromate Cell. A. The glass vessel ; A', E. Carbon ; Z. Zinc ; D, E. Binding screws for the wires ; B. Rod to raise or depress the zinc in the fluid ; C. Screw to fix B. FIG. 77.— Detector. nect the wires from the + and - poles of the Daniell's battery with the binding screws of this instrument, and note that when the circuit is I^O PRACTICAL PHYSIOLOGY. [XZVI. made the needle is deflected from its vertical into a more or less horizontal position, but the angle of deflection is not directly pro- portional 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. LESSON XXYL ELECTRICAL. KEYS-RHEOCHORD. It is convenient to make or break — i.e., close or open — a cur- rent by means of keys, of which there are various forms. 1. Du Bois Key (fig. 78). — It consists of a square 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 (IY.) 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. (L) When the key is closed the current is w,ade, and when it is opened the current is broken (fig. 79). Appa- ratus.— Use a charged Daniell's cell and detector as before, three wires, and a Du Bois key screwed to a table. (a.y As in the scheme (fig. 79) con- nect one wire from 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 wire the other binding screw of the detector with the — pole of the cell. (b.) Observe on depressing the key (i.e., making the circuit) the needle is deflected, on raising it (i.e., breaking the circuit) the needle passes to zero. This method Fig. 78.— Du Bois-Reymond's Friction Key. XXVI] ELECTRICAL KEYS — RHEOCHORD. 151 of using the key we may call that for "making and breaking a current." This method is never used for an interrupted current applied to a nerve or muscle. 3. (2.) When the key is closed the current is said to be "short- circuited." Apparatus. — Daniell's cell, detector, four wires, and a Du Bois key screwed to the table. (a.) As in the scheme (fig. 80) connect the wire from the positive pole of the battery to the outer binding screw of one brass bar of the key, and the other battery wire to the outer binding screw of the other brass bar of the key. Then connect the inner binding screws of both brass bars with the binding screws of the detector. (b.) Observe when the key is depressed or closed, there is no Fig. 79. — Scheme of Du Bois Key. B. Battery; E. Key; N. Nerve; M. Muscle. Fig. 80. — Scheme of Du Bois Key for Short-Circuiting. N. Nerve ; M. Muscle i B. Battery; A". Key. deflection of the needle, i.e., when the current is cut 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 through the detector or nerve, as the case may be. This method of using the key we may call the method of "short-circuiting." 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 short-circuit an induction current. 152 PRACTICAL PHYSIOLOGY. [XXVI. 4. Mercurial Key. — Where a 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. Plug-Key (fig. 8i). — Two brass bars are fixed to a piece of vulcanite. The circuit is made or broken by inserting a brass plug between the bars. Each brass bar is provided 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. 6. Morse Key (fig. 82). — 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 FIG. 81.— Plug-Key. Fig. 82. — The Morse Key. The connections are con- cealed below, but are Biol, A to c, C to C". and C ; when the style of the lever, Z, 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, however, the wires be connected 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 B and C. The current is short-circuited until K is depressed, when the current passes from C to B through the electrode wires. 7. The " Trigger or Turn-Over Key " is referred to in Lesson XXXY. 8. The Contact- or Spring-Key (fig. 83) is also very useful for rapidly mak- ing 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 Fig. 83.— Spring-Key. XXVI.] ELECTRICAL KEYS — RHEOCHORD. 153 bindiDg screw is similarly connected with the little metallic peg at the right-hand end of the tig. Means of Graduating a Galvanic Current. — Besides altering the number, arrangement, or size of the cells themselves, we can use an arrangement to divide the current itself, the battery remaining constant. This is effected by the simple rheochord. FIG. 84.— Scheme of Simple Rheochord. B. Battery; E. Key; W, E. Wire; S. Slider; D. Detector. 9. The Simple Rheochord consists of a brass or German-silver wire, about 1 metre in length, stretched longitudinally along a board, and with its ends connected to binding screws and insula- ted (fig. 84). On the wire there is a " slider " which can be pushed along as desired. Apparatus. — Simple rheochord, Daniell's cell, detector, Du Bois key, live wires. (a.) Arrange the experiment as in fig. 84. "When the slider S is hard up to W, practically all the elec- tricity passes along the wire (W, R) back to the battery. (b.) Pull the slider away from W, and in doing so, more resist- ance is thrown into the battery circuit, and some of the electricity passes along the detector circuit and deflects the needle. The deflection is greater — but not proportionally so — the further the slider is moved from W. 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. 10. Use in the same way a rheochord with two platinum wires, which are connected by an ebonite cup filled with mercury, which slides along on the two wires. Connect the battery — a key being interposed in one wire — with the binding screws on one end of the rheochord, and to the same binding screws connect two wires to the detector. Observe as the mercury cup is pulled away from the binding screws there is a greater deflection of the needle, but the deflection is not in proportion to the distance of the cup. 11. Pohi's Commutator. — Sometimes it is desired to send a current through either of two pairs of wires. This is done by 154 PRACTICAL PHYSIOLOGY. [XXVI. means of Pohl's commutator without the cross-bars (Lesson XXXIII., fig. 102). At other times it is desired to reverse the direction of a current. This is done by Pohl's commutator with cross-bars, or by means of Thomson's reverser. ADDITIONAL EXERCISES. 12. The Rheochord of Du Bois-Reymond is used to vary the amount of a constant current applied to a muscle or nerve (fig. 85). It consists of a long board or box, with German-silver wire— of varying length, and whose resist- ance is accurately graduated — stretched upon it. At one end are a series of brass blocks disconnected with each other above, but connected below by a German- silver wire passing round a pin. These [b blocks, however, may be connected directly by brass plugs, Si S2 . . . S5. From the blocks I and 2 two platinum wires pass from A to the opposite end of the box (Y), where they are insulated. Between the wires is a " slider " (L), con- sisting of two cups of mercury, which slide along the wires. In using the instrument, takeaDaniell's battery and connect its wires to the bind- ing 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 (E) is laid. We have two circuits (a c db and a A B b) ; the wires of the rheochord are inti'oduced 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 (S1-S5) in their places, thus making the several blocks of brass practically one block. In this position the resistance offered by the rheochord circuit is so small as compared with that including the nerve, that prac- tically all the electricity passes through the former and none through the latter. Move the slider away from A, when a certain 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 Si be taken out, more resist- ance 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 plug 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 instrument, that the Fig. 85 PJieochord of Du Bois-Reymond. XXVII. ] INDUCTION MACHINES — ELECTRODES. 155 resistances represented by the several plugs when removed are all multiples of the resistance in the platinum wires on which the slider moves. The instrument is described here for convenience, but its use will be practised later. (a.) Connect a Daniell's cell or a small Grove cell with the binding screws at A and B, introducing a Du Bois key in the circuit. To A and B attach two other wires, and connect them to a Du Bois key, and to the key attach electrudes, thus short-circuiting the electrode circuit. (6.) Prepare a nerve-muscle preparation, lay the muscle on glass, and place the nerve over the electrodes. (c.) Put in all the plugs and push up the slider close to the blocks. Open the short-circuiting key. Make the battery circuit ; perhaps a con- traction may be obtained. Pull the slider away from the blocks, and on making the current con- traction will occur, and perhaps also on breaking it. Take out plug Si, and pull the bridge still farther away, and very probably there will be contraction both at make and break. Proceed taking out plug after plug, and note the result, thereof, will be referred to in Lesson XLV. 2. 13. Thomson's Reverser (fig. 86) 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. FIG. 86. — Thomson's Reverser. The result, and explanation LESSON XXVII. INDUCTION MACHINES-ELECTRODES. 1. Induced or Faradic Electricity is most frequently employed for physiological purposes. 2. Induction Apparatus of Du Bois-Reymond. — In fig. 88 the primary coil (R/) consists of about 150 coils of thick insulated copper wire, the wire being thick to offer slight resistance to the 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 (I) is attached, so that the distance of the secondary from the primary spiral may be ascertained. At the left end of the apparatus is a Wagner's hammer as adapted by Neef, which is an automatic arrangement for opening and breaking the primary circuit. When Neef's hammer is used to obtain what 156 PRACTICAL PHYSIOLOGY. [XXVII. is called an interrupted current, the wires from the battery are connected as in the figure, but when single shocks are required, the wires from the battery are connected with a key, and this again with the two terminals of the primary spiral, S" and S"'. 3. New Form of Induct orium. — Fig. 88 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- Fig. 87. — Induction Apparatus of Du Bois-Reymond. -R'. Primary, R". Secondary spiral ; B. Board on which R" moves ; I. Scale ; + - . Wires from battery ; P', P". Pillars ; H. Keef's hammer; B'. Electro-magnet; S'. Binding screw touching the steel spring (H) ; S" and S'". Binding screws to which are attached wires when ISeef's hammer is not required. duced current ; on the contrary, the strength of the induced currents undergoes 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. Ordinary Hand-Electrodes (fig. 89). — Take two pieces of flexible gutta-percha coated wire (No. 20) 60 cm. long, and two pieces of thick glass tubing 8 cm. long, having a bore sufficient to admit the wire. Push a wire through each tube, and allow the XXVIL] INDUCTION MACHINES — ELECTRODES. 157 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 pieces of Iso. 20 gutta- percha 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 copper wires solder thin silk-covered wires, Fig. 88.— Inductorium with Secondary Coil Moving in a Vertical Slot. FIG. B9. — Hand-Elec- trodes, such as a stu- dent is required to make for himself. and to the free ends of the latter solder a short length (2 cm.) of thick uncoated copper wire. A very handy holder is made by thrusting two fine insulated wires (Iso. 36) through the bone handle of a crotchet-needle. 7. Shielded Electrodes. — For some purposes, e.g., stimulation of the vagus, these electrodes are used, i.e., the platinum terminals are exposed only <>n one side, the other being sunk in a piece of vulcanite (tigs. 104, E, 197^. A par of shielded electrodes is easily made by fixing the ends of two tine wires — arranged parallel to each other and about one-eighth of an inch apart — in a 158 PEACTICAL PHYSIOLOGY. [XXVII. thin layer of gutta-percha cement. A little of the cement is scraped off to expose a small piece of both wires. 8. Du Bois-Reymond Electrodes (fig. 90). — 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). 9. For Non-Polarisable Electrodes. See Lesson XLI. 10. Polarisation of Electrodes. — Apparatus. — Pair of ordinary electrodes (fig. 89), two wires, Du Bois key, spring key, Daniell's cell, frog, and instruments. (a. ) Pith a frog (Lesson XXIX. 1), lay it belly downwards on a frog-plate, and expose one sciatic nerve. FIG. 90.— Du Bois-Eeymond's Platinum Electrodes. The nerve is placed over the two pieces of platinum, P, which rest on glass ; B. Universal joint ; V. Support. (b.) Screw the Du Bois key to the table, place the electrodes under the sciatic nerve, and connect their other ends each with the outer binding screw of the brass plates in the Du Bois key. Close the key, and observe that no contraction of the leg muscles occurs. (c.) By two wires connect a Daniell's cell with the Du Bois key, introducing a spring key in the circuit. Open the key to allow the constant current to pass through the nerve for 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. The contractions are due to polarisa- tion of the electrodes. XXVIII.] SHOCKS AND CURRENTS. 1 59 LESSON XXVIII. SINGLE INDUCTION SHOCKS - INTERRUPTED CURRENT-BREAK EXTRA-CURRENT-HELM- HOLTZ'S MODIFICATION. 1. Single Induction Shocks.— Apparatus.— Daniell's cell, induc- tion machine, five wires, two Du Bois keys (or one Du Bois and one spring or contact key), and ordinary electrodes. (a.) Connect one wire from the battery to the binding screw, S", of the induction machine (fig. 87). Join the other wire from the battery to a Du Bois key (or spring contact key), and use the third wire to connect the key with the binding screw, S'". The Du Bois key is used according to the first method, i.e., for make and break, so that the primary current can be made or broken at will. 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 as in fig. 97. (b.) 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 thumb moistened with water. Close the key in the primary cir- cuit, i.e., make the circuit, and instantaneously at the moment of making, a shock is induced in the secondary coil, R", and is felt on the tip of the tongue or finger. It is called the closing or make induction shock. All the time the key is closed the gal- vanic current is circulating in the primary spiral, but it is only when the primary current is made or broken that a shock is induced in the secondary spiral. (c.) Break the primary current by raising the key, and instan- taneously a shock is felt as before; this is the opening or break induction shock. (d.) Observe that the break is stronger than the make shock. Push 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. Observe that the break shock is felt first, and on pushing the secondary nearer the primary coil both shocks are felt, but the break is stronger than the make shock. (e.) Remove the secondary spiral from its slot, and place it in i6o PRACTICAL PHYSIOLOGY. [XXVIII. line with and about 15 cm. from the primary. Rotate the secon- dary coil so as to place 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 by using Neef 's Hammer. — Apparatus. — The same as for single shocks. (a.) Connect the battery wires as in fig. 87, i.e., to the binding screws in the erect pillars, P' ( + ) and P" ( — ). Introduce a Du Bois key as for the make and break arrangement. The automatic vibrating spring, or Neef's hammer, is now included in the pri- mary circuit. Set the spring vibrating. Make the current by depressing the handle of the key. The elastic 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 elastic 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. (b.) While Neef 's hammer is vibrating, apply the electrodes to the tongue or finger as before, noting the effect produced and how it varies on altering the distance between the secondary and primary spirals. (c.) Note also how the strength of the induced shocks varies with the angular deviation of the secondary spiral, the dis- tance between the two spirals being kept constant (p. 156). 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 in- Yiq. 9i.— Scheme of the Break-Extra Current, fluence on the others. When B. Battery; K. and K'. Keys ; P. Primary *■, onrrpnt is made the direc- coil; N. Nerve; M. Muscle. Lne current is maae, biie unec tion of the extra-current is against that of the battery current, but at break it is in the same direction as the battery current. Apparatus. — Daniell's cell, two Du Bois keys, five wires, induction coil, ordinary electrodes (and nerve-muscle preparation). (a.) Arrange the apparatus according to the scheme (fig. 91). Notice that both keys and the primary coil of the induction XXIX] PITHING — CILIARY MOTION, ETC. 161 machine are in the primary circuit, both keys being so arranged that either the primary coil, P, or the electrodes attached to key K', can be short-circuited. (b.) 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). (c.) 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. 87), P' and P", or to a and e (fig. 92). In fig. 92 connect a wire from a to /, thus bridging rupter. Elevate the screw (/) out of reach of the spring (c), but raise the screw (d) until it touches the spring at every vibration. By this means the make and break shocks are nearly equalised, but both shocks are weaker. Fig. 92. — Helmholtz's Modification of Neef's Hammer. As long as c is not in contact with d, fi 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/. A'. Batteiy. or " short-circuiting " the inter- LESSON XXIX. PITHING— CILIARY MOTION-NERVE-MUSCLE PREPARATION-NORMAL SALINE. 1. To Pith a Frog. — Wrap the 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 linger until the skin over the back of the neck is put on the L 1 62 PRACTICAL PHYSIOLOGY. [XXIX. stretch. With the nail of the right index-finger feel for a de- pression 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, and 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 blade, else two large blood-vessels will be injured. The operation should be performed without losing any blood. 2. Ciliary Motion. (a.) Pith a frog, destroying the brain and the spinal cord. Place the frog on its back. Divide the lower jaw longitudinally, and carry the incision backwards through the pharynx and oeso- phagus. Pin back the flaps. Moisten the 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. Repeat the experiment, and determine the time the flag takes to travel a given distance. (c.) Grains of charcoal or Berlin blue are carried backwards in a similar manner. (d.) Apply heat to the preparation, and observe that the cork travels much faster. 3. Anatomy of the Nerve-Muscle Preparation. — Before mak- ing this preparation, the student must familiarise himself with the anatomy of the lower limb of the frog. On a dead frog, or on a dissection of a frog already prepared, study the arrangement of the muscles, as shown in fig. 93. The skin of the frog is sup- posed to be removed, and the frog placed on its belly, and the muscles viewed from behind. On the outside of the thigh, the triceps femoris (tr.), composed of the rectus anterior (r.a.), the vastus externus (v.e.), and the vastus internus, not seen from behind. On the median side, the semi-membranosus (s.m.), and between the two the small narrow biceps (b.). Notice, also, the coccygeo- iliacus (c.i.), the gluteus (gl.), the pyriformis (_£>.)> and the rectus internus minor (r.?.). In the leg, the gastrocnemius (g.), with its tendo Achillis, the tibialis anticus (t.a.), 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," gently tear through XXIX.] PITHING — CILIARY MOTION, ETC. 163 the fascia covering the thigh muscles, and with the blunt point of the finder separate the semi-membranosus from the biceps, and in the interval between them observe the sciatic nerve and the femoral vessels. Carefully isolate both, beginning at the knee, where the nerve divides into two branches — the tibial and pero- neal— and work upwards (fig. 94). B op— ! FIG. 93.— The Muscles of the Left Leg of a Frog from behind, ex. Coccy- geo-iliacus ; (il. Gluteus; p. Piri- formis; r.a. Rectus anterior; v.e. Vastus extemus; tr. Triceps; /•.*'. Reet. int. minor; x.m. Semi-mem- branosus ; b. Biceps ; g. Gastro- cnemius ; t.a. Tibialis anticus ; ye. Peroneus. 4.— Distribution of the Sciatic Nerve (I.) of the Frog (see al- 03). s.t. Semitendinosus ; ad . Ad- duotoi magnus; (II.) its tibial; and (III.) peroneal divisions. (/>. ) Follow the nerve right upwards to its connection with the vertebral column, and observe that it is necessary to divide the pyriforrnis (/)) with small scissors, and also the ilio-coccygeal muscle, when the three spinal nerves — the 7th, Sth, and 9th — which form the sciatic nerve, come into view. 1 64 PRACTICAL PHYSIOLOGY. [XXX. 5. Normal Saline. — Dissolve 7.5 grams of dried sodic chloride in 1000 cc. of distilled water. This is the best fluid to use to moisten tissues. LESSON XXX. NERVE -MUSCLE PREPARATION - STIMULATION OP NERVE - MECHANICAL, CHEMICAL, AND THERMAL STIMULI. 1. Prepare a Nerve-Muscle Preparation. — Apparatus. — A frog, pithing-needle or " seeker " in handle, narrow-bladed scalpel, a small and a large pair of scissors, forceps, towel, and a porcelain plate on which to place the frog. (A.) (a.) Pith a frog with a pithing-needle, destroying the brain and spinal cord, and place the frog on its belly on a porce- lain plate. With the small scissors make an 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 urostyle. Reflect the skin, which is readily done, as there are large lymph sacs between it and the muscles, thus exposing the muscles shown in fig. 93. (b.) Gently separate the semi-membranosus and biceps with the " seeker," and bring into view the sciatic nerve and femoral vessels. Still working with the seeker and beginning near the knee, clear the sciatic nerve of any connective tissue around, but on no account is the nerve to be touched with forceps, nor is it to be scratched or stretched. With the small pair of scissors divide the pyriformis and ilio-coccygeus, and trace the nerve up to the vertebral column. (c.) With a sharp-pointed large pair of scissors 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 iliac bone above and below, and remove it with the muscles attached to it. The lumbar plexus now comes clearly into view. Bisect lengthways the three lower vertebrae, and use the quadri- lateral piece of bone by which to manipulate the nerve. With the forceps lift the fragment of bone, and with it the sciatic nerve ; trace the latter downwards to the knee, dividing any connec- tions and branches with fine scissors. If the parts tend to become dry, moisten the whole preparation with normal saline solution. XXX.] NERVE-MUSCLE PREPARATION, ETC. 165 (d.) Divide the skin over the gastrocnemius, and expose this muscle. Divide the tendo Achillis below its fibro-cartilage, lift the tendon with a pair of 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 injury, clear the muscles away from the lower end of the femur, and then divide, with the large pair of scissors, the femur itself about its middle. This preparation (fig. 95) consists, there- fore, of the gastrocnemius, and the whole length of the sciatic nerve, to which is attached a fragment of bone, by which the preparation can be manipulated without in- juring 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 method is sometimes adopted. Destroy the brain and spinal cord of a frog. With the left hand seize the hind-limbs and hold the frog 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 all 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. At once the whole 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 : — (1.) 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 common salt or glycerin. (3.) Thermal, e.g , applying the end of a heated wire to the Fig. 95. — Nerve-Muscle Pre- paration. S. Sciatic nerve — the fragment of the spinal column is shown ; F. Femur /. Tendo Achillis. not and nerve. (4-) Electrical — (a.) Continuous current, (b.) Single induction sh ocks. (c.) Interrupted current. 1 66 PRACTICAL PHYSIOLOGY. [XXX. 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. — Frog-pithing needle, scalpel, scissors, forceps, straw flag, pins, muscle-forceps, camel's-hair brush, saturated solution of common salt in a glass thimble, ammonia, copper wire, spirit lamp or gas-flame. 4. Mechanical Stimulation. (a.) Pith a frog, destroying its brain and spinal cord. Remove the skin, and proceed as directed by the method (Lesson XXX. 1) for preparing a nerve-muscle preparation, as far as the isola- tion of the sciatic nerve, but modify the subsequent details as follows : — (6.) After the nerve is cleared as far as the spine, clear all the muscles away from the femur, and divide the latter about its middle. Divide the sciatic nerve as high up as possible. The preparation consists of the leg, the lower end of the femur, and the sciatic nerve, terminating in the leg muscles. Pin a straw flag to the toes by means of two pins. Fix the femur in a clamp or pair of muscle-forceps, sup- ported on a stand, and shown in fig. 96, taking care that the gastrocnemius is upwards. The nerve hangs down, as fig. 96.— straw Flag attached shown in the figure, and must always be to a Frog's Leg fixed in a . i , j •,■> i> v • V i Clamp. N. Nerve ; F. Flag, manipulated with a camel s-nair brush dipped in normal saline. (c.) Pinch the free end of the nerve sharply with forceps ; the muscles contract and the straw flag is suddenly raised. Cut off the killed part of the nerve, and observe that contraction also occurs. {d.) Prick the muscle with a needle ; it contracts. 5. Thermal Stimulation. (a.) To the same preparation apply gently, either to muscle or nerve, a hot copper 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 some saturated solution of common salt in a small glass thimble, or place a drop on a perfectly clean glass slide, 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 XXXI.] ELECTRICAL STIMULATION. 167 it. After a few moments, the individual joints of the toes begin to twitch, and by-and-by the whole limb is thrown into irregular spasms, ultimately terminating in a powerful, more or less con- tinuous, contraction or spasm of the whole musculature, consti- tuting tetanus. Cut off the part of the nerve affected by the salt, and the spasms will cease. (b.) Use the same 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 nerve to the vapour of strong 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 pass 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 muscle. Apply the ammonia to the muscle ; it will con- tract. LESSON XXXI. SING-LB AND INTERRUPTED INDUCTION SHOCKS —TETANUS-CONSTANT CURRENT. 1. Electrical Stimulation — Single Induction Shocks. — Ap- paratus.— Frog, DanielPs cell, induction machine, two Du Bois keys (or one spring contact key and one Du Bois key), five wires, flexible electrodes, (a.) Arrange a cell and induction machine for single induc- tion shocks according: to the scheme (fig. 97). A spring contact key is more convenient in the primary circuit. Flexible electrodes are fixed to the short- circuiting key (K') in the secondary cir- cuit, and over them the nerve is to be placed. (6.) Expose the sciatic nerve in a pithed frog, place the elec- trodes— preferably a pair fixed in ebonite, and so shielded that only one surface of their platinum terminals is exposed under Fig. 97.— Scheme for Single Induction Shocks. B. Bat- tery ; K, K . Keys ; J'. Primary, and S. Secondary coil of the induction machine ; 2V. Nerve ; M. Muscle. 1 6.8 PRACTICAL PHYSIOLOGY. [XXXI. it. Or use the simple shielded electrodes described in Lesson XXVII. 6. Pull the secondary coil (S) far away from the primary (P), raise the short-circuiting key (K'), make and break the primary circuit by means of the key (K). At first there may be no contraction, but on approximating 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. Record 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. 2. Interrupted Current. (a.) Arrange the induction machine so as to cause Neef's hammer to vibrate as directed in Lesson XXVIII. 2. On apply- ing the electrodes to the sciatic nerve or gastrocnemius muscle, at once the muscle is thrown into a state of rigid spasm or con- tinuous contraction, called tetanus, this condition lasting as long as the nerve or muscle is stimulated, or until exhaustion occurs. 3. Constant Current. — Apparatus. — One, two, or three Daniell's cells, Du Bois key (or, preferably, a simple make and break key), four wires and pair of electrodes, forceps, and nerve- muscle preparation. (a.) TJse two Daniell's cells. If two or more Daniell's cells be used, always connect them in series, i.e., the positive pole of one cell with the negative pole of the next one. Connect two wires, as in fig. 98, to the free + and - poles of the battery B, and introduce a Du Bois key (K') so as to short- circuit the battery circuit. Fix two shielded electrodes in the other binding-screws of the Du Bois key, and having prepared a fresh nerve - muscle preparation, lay the Ss-^ B//::\>y' divided sciatic nerve (N) across them, as ^^^^X^//^ shown in fig. 98. A simple key to make or break the current is preferable to the FlGc^rent i^Battery; :j!7. short-circuiting key, as the latter allows Short-circuiting key; jv. polarisation currents to pass when it is Nerve ; M. Muscle. r ■*■ closed. (b.) Make and break the current, and a single muscular con- traction or twitch is obtained, either at making or breaking, or both at making and breaking. Notice that if the key be raised to allow the current to flow continuously through the nerve, no contraction occurs, provided there be no variation in the intensity XXXI.] ELECTPJCAL STIMULATION. 169 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. (d.) 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. Dead Muscle and Nerve. — Immerse a nerve-muscle pre- paration for a few minutes in water at 40° C. Both are killed, and none of the above stimuli cause contraction. 5. The Sartorius. — The student gets a clear idea of the short- ening and thickening which occur when a muscle contracts by working with the sartorius muscle, because its fibres are arranged in a parallel manner. (a.) Pith a frog, skin it, lay it on its back, and dissect off the long narrow sartorius from the inner side of the thigh. Stretch it on a slip of glass (fig._ 99, s). (b.) 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. Observe 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. 6. Unipolar Stimulation. — Apparatus. — Daniell's cell, induction machine, Du Bois key, muscle-chamber, four wires. (a.) Connect the Daniell to the primary Fio. 99.— Muscles of the Left coil of the induction machine either for w^*^j£!££?Z single shocks or tetanus, introducing a Du Sartorius ; ad'. Adductor -r, • i • ,1 • m. r\ , • longus ; vi. Vastus interims. Bois key in the circuit. Connect one wire (See figs. 93 and 94.) with the secondary coil, and attach it to one of the binding screws on the platform of the muscle-chamber, to which the nerve electrodes are attached. See that the battery and induction machine are perfectly insulated by supporting them on blocks of paraffin. (b.) Prepare a nerve-muscle preparation, and arrange it in the 170 PEACTICAL PHYSIOLOGY. [XXXII. mnscle-chamber in the usual way, laying the nerve over the electrodes. One of the electrodes will therefore be connected with the secondary circuit. (c.) Make and break the primary circuit; there is no con- traction. (d.) Destroy the insulation of the preparation by touching the muscle, or what does better, allow the brass support 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 muscle contracts. Touch the secondary coil and contraction results. LESSON XXXIL RHEONOM- TELEPHONE EXPERIMENT— DIRECT AND INDIRECT STIMULATION OP MUSCLE- RUPTURING STRAIN OP TENDON - MUSCLE SOUND-DYNAMOMETERS. 1. Fleischl's Rheonom. — This instrument (fig. ioo) is very useful for showing Du Bois-Reymond's law, that it is variations in the intensity of a galvanic current which excite a motor nerve. It 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 bind- ing screws attached to two bent strips of zinc, moves on a vertical support. (a.) Connect two Daniel!' s cells with the fig. too.— Fleischl's binding screws A and B, introducing a Du Bois key in one wire. Attach the elec- trodes, introducing a Du Bois key to short-circuit them, to the binding screws, C and D. Fill the groove with a saturated solu- tion of zinc sulphate. (&.) Arrange the nerve of a nerve-muscle preparation in the usual way over the electrodes. 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. Then suddenly rotate the handle with its two zinc arms ; this is equivalent to a sudden variation of the intensity of the current ; XXXII.] STIMULATION OF MUSCLE. I7I the current, of course, continuing to pass all the time. The muscle suddenly contracts. 2. Direct and Indirect Stimulation of Muscle. — When tbe stimulus is applied directly to the 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. («/) Arrange a nerve-muscle preparation, and an induction machine for single or interrupted shocks (Lesson XXXI. 1). (b.) Test first the strength of current — as measured by the distance between the secondary and primary coils — which causes the muscle to contract when the stimulus is applied to the nerve, i.e., for indirect stimulation. (c.) Then with the secondary still at the same distance from the primary, try if a contraction is obtained on stimulating the muscle directly. It will not contract ; but make the current stronger, and it will do so. ADDITIONAL EXERCISES. 3. Muscle Sound. (a.) Insert the tips of the index-fingers into the auditory meatuses, forcibly contract the biceps muscles. A low rumbling sound is heard. (6.) 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 preparation 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 stnng 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. (6.) Into the scale-pan place weights, and observe the weight required to rupture the tendon or muscle. Usually the muscle is broken first, and the weight added to the scale 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 1 as been dead for twenty -four or 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. (b.) 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. 172 PRACTICAL PHYSIOLOGY. [XXXIII. LESSON XXXIII. INDEPENDENT MUSCULAR EXCITABILITY -AC- TION OP CURARE-ROSENTHAL'S MODIFICA- TION-POHL'S COMMUTATOR. 1. Independent Muscular Excitability and the Action of Curare. — Curare paralyses the intra-muscular terminations of the motor nerves. — Apparatus. — Daniell's cell, induction machine, two keys, five wires, 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-neeedle, fine threads, pithing-needle, 1 per cent, watery solution of curare in a glass-stoppered bottle, fine hypodermic syringe or glass pipette, frog. (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. (b.) Pith a frog, destroying only its brain, and by means of a hypodermic syringe or a fine glass pipette inject into the ventral or dorsal lymph-sac one or two drops of a 1 per cent, watery solution of curare. 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.) Place the frog on its back. Expose the heart, and observe that it is still beating. Take care to lose no blood. (d.) Expose the sciatic nerve on one or both sides. (i.) Apply the shielded electrodes under them, and stimulate the nerves with tetanising shocks ; there is no contraction. (ii.) Apply the electrodes to the muscles ; they contract. Therefore curare has paralysed, the voluntary motor nerves, out not the muscles. 2. On what Part of the Nerve does the Curare Act ? (a.) Keep the induction apparatus as in the previous experi- ment. (b.) Pith a frog, destroying only its brain. Carefully expose the sciatic nerve and the accompanying artery and vein on one XXXIII. ] INDEPENDENT MUSCULAR EXCITABILITY. 1 73 side, e.g., the left, taking great care not to injure the blood-vessels, which are to be carefully isolated for a short distance with a iinder. Thread a fine aneurism-needle with a fine silk thread. Moisten the thread with salt solution, and gently pass it under the sciatic artery. Withdraw the needle and ligature the artery. Instead of ligaturing merely the artery, it is better to isolate the sciatic nerve, and then to tie a stout ligature round all the other structures of the thigh. In this way none of the poison can pass by a collateral circulation into the parts below the ligature. (c.) Inject a few drops of a 1 per cent, solution of curare into the ventral lymph-sac, either by means of a hypodermic syringe or a fine pipette. In a short time the poison will be carried to every part of the body except the left leg below the ligature. Observe that the animal is rapidly paralysed, but if the non- poisoned leg (left) is pinched, it is drawn up, while the poisoned leg (right) is not. ((/.) Wait until the animal is thoroughly under the influence of the poison, and then expose both sciatic nerves as far up as the vertebral column and as far down as the knee. (i.) Stimulate the right sciatic nerve. There is no contraction. Therefore the poison has acted either on nerve or muscle. (ii.) Stimulate the right gastrocnemius muscle; it contracts. Therefore the poison has acted on some part of the nervous path, but not on the muscle. (iii.) Stimulate the left sciatic above the ligature ; the left leg contracts. Observe that the part of the nerve above the ligature was supplied with poisoned blood, and has been under the influence of the poison, 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. (e.) Apply several drops of a strong solu- tion of curare to the left gastrocnemius, and after a time stimulate the left sciatic nerve ; there is no contraction, but on stimu- lating the muscle itself contraction takes fig. 101.— Pohl'a Commu- t tutor with Cross-bars in. place. 3. Pohl's Commutator (fig. 101) is used for sending a cur- rent along two different pairs of wires, or for reversing the direction of the current in a pair of wires. It consists of a round 174 PRACTICAL PHYSIOLOGY. [XXXIII. or square wooden or ebonite block with six cups, each in con- nection 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 wires, the cross-bars are removed and wires are attached to all six cups, 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, beside the battery wires, is attached to the mercury cups, e.g., to 3 and 4, or 5 and 6, the cross-bars remaining in. ADDITIONAL EXERCISES. 4. 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 as before. After complete paralysis occurs, dissect out both legs with the nerves attached, but retain the legs, as in fig. 102. Attach straw flags (NP and P) of diffe- rent colours to the toes of both legs by pins, and fix both femora in muscle-forceps (F) with the gas- trocnemii uppermost. Place the nerves (N) on the platinum points of Du Bois- Raymond's electrodes (fig. 90). (b.) Arrange the induction appa- ratus as in fig. 102. The primary coil is as before, but the terminals of the secondary coil are connected by two wires with the piers of a Pohl's commutator (fig. 10 1 ) with out cross-bars (H). Two other wires pass 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. Fig. 102.— Scheme of the Curare Experiment. Place the commutator on a meat B Battery ; I. Primary, iT. Secondary plate and fill its holes with mer- spiral ; N Nerves; F. Clamp ; NP. Non- cur„ The commutator enables the poisoned leg ; P. Poisoned leg ; C. Com- . . • • . 1 j mutator; K. Key. The short-circuiting tetamsmg currents to be passed key in the secondary circuit is omitted in either through both nerves or both the diagram. muscles. It is more convenient if the secondary circuit have a ke}T, eo that it may be short-circuited when desired. (i.) Set Neef's hammer going, and turn the handle of the commutator so XXXIV.] THE GRAPHIC METHOD. 1 75 that the current passes through both nerves ; only the non-poisoned leg (XP) contracts. (ii.) Reverse the handle and pass the current through both muscles; both contract. (iii.) Rosenthal's Modification. — Pu^h the secondary spiral far away from the primary, and pass the current through both muscles. At first, if the spirals be sufficiently far apart, there is no contraction in either muscle. Gradually push up the secondary spiral, and notice on doing so that the non-poisoned limb contracts first, and that on continuing to push up the secondary spiral, both muscles ultimately contract. 5. Action of Curare— Bernard's Method. — The student, if he desires, can prepare two nerve-muscle preparations, and dip the nerve of one (A) and the muscle of the other (B) into a solution of curare in two watch-glasses. On stimulating the nerve of A, its muscle contracts ; on stimulating 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 paralysed. LESSON XXXIV. THE GRAPHIC METHOD-MOIST CHAMBER- SINGLE CONTRACTION-WORK DONE. 1. Recording Apparatus. — For this purpose a revolving cylin- der covered "with smoked glazed paper or other moving sur- face is required. The velocity of the moving surface is usuallv 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 reed (p. 188). It does not matter particularly what form of recording drum is used, provided it moves smoothly and evenly, and is capable of being made to move at different rates as required. In Hawksley's form this is accomplished by placing the drum on different axles, moving at different velocities. In Lud wig's form (fig. 103) this is done by moving a small wheel, n, on a large brass disc, D. Where a number of men have 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 move the drums. This is the arrange- ment adopted in the Physiological Department of Owens College, so that a large 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. 176 PRACTICAL PHYSIOLOGY. [XXXIV 2. Cover the Cylinder with 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 which moves it, and is then covered with a strip of paper, the latter being laid on evenly to avoid folds. One edge of the 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 gas-burner, or paraffin lamp — the former is prefer- FlG. 103.— Ludwig's Revolving Cylinder, R, moved by the clockwork in the box A, and regulated by a Foucault's regulator on the top of the box. The disc, D, moved by the clockwork, presses upon the wheel n, which can be raised or lowered by the screw L, thus altering the position of n on D, so as to cause the cylinder to rotate at different rates. The cylinder itself can be raised by the handle U. On the left side of the figure is a mercurial manometer. able. 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. 3. General Rules to be Observed with every Experiment. (1.) In every experiment arrange the apparatus completely, cover the drum with paper, and smoke it, before beginning the dissection of the frog. (2.) See that the secondary circuit is "short-circuited." (3.) Test all the connections stage by stage as they are made. XXXIV.] THE GRAPHIC METHOD. i/7 (4.) Each tracing is to be inscribed with the name of the individual who made it, the date, and what it is intended to show, and any other particulars it is desired to record. It is then to be varnished, and the varnish allowed to dry. 4. Myographs. — Various forms are in use, but most of them consist of a lever which is raised by the contracting muscle, and so arranged as to record its movement on a smoked surface of paper or glass. Taking advantage of the fact that a muscle when it contracts becomes both shorter and thicker, myographs have been constructed on two principles : — (a) Shortening of muscle attached to a lever. (/?) Thickening of muscle on which the lever rests. Fig. 104.— Moist Chamber. i\'. Glass shade-; E. Electrodes; L. Lever; TT. Weight; TM. Time-marker ; other letters as in previous figures. The surface of the myograph on which the style of the lever writes may be — (1.) Stationary (Pfliiger's). (2.) Rotatory (Helmholtz's). (3.) Swinging pendulum (Fick's). (4.) Moved from side to side by a spring, either vertically (Du Bois-Reymond) or horizontally. 5. Moist Chamber (fig. 104). — To prevent a nerve- musjle preparation from getting dry, it must be enclosed in a moist chamber, which is merely a glass shade placed over the pre- paration, while to keep the air and the preparation moist, the sides of the shade are covered with blotting-paper moistened with water. M I78 PRACTICAL PHYSIOLOGY. [XXXIV. 6. Varnish for Tracings. — The tracing is simply drawn through the varnish and then hung up to dry. (a.) A very good varnish consists of gum mastic or white shellac dissolved to saturation in methylated spirit. (b.) 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. 7. Single Contraction or Twitch. — Apparatus. — Recording drum, Daniell's cell, Morse key, induction machine, Du Bois key, wires, electrodes, moist chamber and lever, moist blotting- paper, stout ligatures, hook, pins, lead weight (20 grams), frog, and the necessary instruments. (a.) Arrange the recording apparatus and the drum to move slowly. Cover the drum with glazed paper, and afterwards smoke it over a glass flame, and fix it in position. (b.) Arrange the apparatus as follows : — One Daniell's cell and a Morse key in the primary circuit, the secondary circuit of the induction machine short-circuited, and with wires to go to the binding screws on the platform of the moist chamber on the myograph (fig. 104). [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. 3).] (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 a hook like the letter S, made by bending a pin. Manipulate the nerve with a camel's-hair pencil. Arrange the preparation in the moist chamber by fixing the femur in the muscle clamp, and by means of a stout ligature thread attach the hook in the tendo Achillis to the writing-lever under the ebonite or wooden stage of the moist chamber. See that the muscle or ligature goes clear through the hole in the stage, and that the hook does not catch on anything. Adjust the height of the muscle clamp so that the writing-lever is horizontal. 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 near where the muscle is attached to it by a weight of about 20 grams, and make the lever itself horizontal. The weight may be hung directly upon the lever or placed in a scale-pan attached to the lever. Arrange the point of the lever so that it writes on the cylinder. The writing-style on the tip of the lever may be made XXXTV ] THE GRAPHIC METHOD. :". of verv thin copper foil or parchment papri. : ~:ened on tc : lever with sealing- wax or telegraph composition. 8. According as the recording surface is stationary or moving when the muscle contracts and raises the lever, either a vertk line or a curve will be made upon * er. In the latter case the form of the curve will vary with the velocity of the drum. Arrange experiments for both. A. Begin with the recording cylinder stationary. Push the secondary coil far away from the primary, open the key in the secondary circuit, and make and break the primary circuit. There may be no contraction. Close the secondary cir- cuit key. '.rradually approximate the secondary coil, open the sh . - FIG. 105.— Muscle-Curve ::'--: _ i ^istroenemius. The lower line indicates time, each double vibration (Z>. T.) = rJ; 5r :. circuiting key. and break the primary circuit by means of the Morse key in it. Observe when the first feeble contraction is obtained = minimal contraction. Make the primary circuit, there is no contraction. TLe break shock is. therefore, stronger than the 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. Move the drum a short dis- tance with the hand ; the lever will inscribe a horizontal or base line, the abscissa. 1 rradually approximate the secondary spiral, and from time to time test the effect of the make and break shocks, after each test moving the cylinder with the hand, and recording the result l80 PRACTICAL PHYSIOLOGY. [XXXIV. as to M or B, and the distance in centimetres of the secondary from the primary coil. After a time a make contraction appears, and on pushing up the secondary coil the make contraction becomes as high as the break. (d.) 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 make and break contractions obtained with each strength of current close together. Their relative heights can then be readily compared. B. Arrange the experiment as in A, but allow the cylinder to revolve at a moderate speed, 25-30 centimetres per second ; the writing-style records an even horizontal line =- the abscissa. (a.) Select a strength of stimulus which is known to cause a contraction, and while the cylinder is revolving, cause the muscle to contract either by a make or break shock. Study the characters of the ' ' muscle-curve " (fig. 105), noting par- ticularly the latent period, the ascent and descent, i. e.., the period of shortening and that Fig. 106.— Frog's Gastrocnemius Stimulated by a Single of elongation of the Make (M) and Break (B) Shock, the distance between muSple the primary and secondary coil being the same for both ' shocks. In the lower figure the muscle has somewhat (h.\ Vary the velo- fatigued- city of movement of the cylinder, and observe how the form of the curve varies with the variation in velocity of the cylinder (fig. 106). (c.) Remove the tracings in A and B, and varnish them. In this case the moment of stimulation is not recorded. 9. The Work Done during a Single Muscular Contraction. — After the tracing of B is dry,- from the abscissa draw vertical lines or ordinates,. and measure their height in millimetres. Measure the length of the lever, and from this calculate the actual amount of shortening of the muscle itself. Multiply this by the weight lifted, and the product is the work done expressed in gram-millimetres. (a.) Measure the height of the tracing from the base line or abscissa. This is most conveniently done by a small paper milli- metre scale fixed to an ordinary microscopic slide. The work done ( W) is equal to the weight (w) lifted multiplied by the height (h) to which it is lifted — W = wh. XXXIV.] THE GRAPHIC METHOD. 1S1 But, of course, a long lever being used, the tracing is much higher than the actual shortening of the muscle. (b.) To determine the exact amount of the lift, one must know the length of the level 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. (c.) 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. 10. The Crank-Myograph (fig. 107) is fixed on a suitable sup- port, so that it can be adjusted to any height desired. The experiment is arranged in exactly the same way as for 7. (a.) Use one hind-limb of a pithed frog; pin the femur firmly to the cork plate of the myograph covered with blotting-paper moistened by normal saline, the tibia being in line with the writ- ing lever. Or take the pithed frog, lay it on the frog-plate of Fig. 107.— Crank Myograph. W. W. Block of wood; M. Muscle; F. Femur; P. Pin to fix F ; L. Lever ; WT. Weight; «. Screw for after-load ; C. Cork; B, B. Brass box. the myograph, expose the gastrocnemius, and proceed as above. Detach the tendo Achillis, tie a stout ligature round its sesamoid bone, and fix the ligature to the short arm of the lever, add a weight of 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 through the upper and lower end of the gastrocnemius muscle. (b.) Arrange the style of the lever so that it writes on the cylinder, and repeat the experiments of either A or B, or both. (c.) Use different weights — 5 — 20 — 50 grams — and observe how the form of the curve varies on increasing the weight attached to the lever. 11. After-Load. — In the crank-myograph, under the lever, is a screw on which the horizontal arm of the bell-crank rests (tig. 107, a), so that the muscle is loaded only during its contraction. 1 82 PRACTICAL PHYSIOLOGY. XXXV. 12. Interrupted Current. — If, instead of single shocks, the induction apparatus be so arranged that Neef's hammer is in action, then, on stimulating the muscle or nerve, tetanus is obtained (Lesson XXXI. 3), and the curve of a tetanised muscle recorded. 13. Constant Current on a Muscle. — Curarise a frog, and after the curare has paralysed the terminations of the motor nerves, dissect out the gastrocnemius and arrange it to record its contrac- tions in the ordinary way. Let the muscle be stimulated directly by make and break shocks from a Daniell's battery of two or more cells. Observe the effect of the make and break shocks separately, but note that no contraction takes place while the current passes. Of course, the muscle cannot be caused to contract through its nerve, as the terminations of the motor nerve have been paralysed by the curare. LESSON XXXT. ANALYSIS OF A MUSCULAR CONTRACTION-PEN- DULUM MYOGRAPH -SPRING MYOGRAPH- TIME-MARKER-DEPR^Z SIGNAL. 1. Muscle-Curve by the Pendulum-Myograph. (a.) Cover the oblong glass plate with glazed paper, smoke its surface, and fix it to the pendulum. The plate must be so adjusted that the pendulum on being set free from the "detent" (fig. 108, C) shall be held by the "catch" (C). Test this. (b.) Arrange the induction apparatus for single shocks as in fig. 108, but short-circuit the secondary circuit, interposing in the primary circuit the trigger-key or knock-over key of the pendulum-myograph (fig. 108, K'). (c.) Make a nerve-muscle preparation, fix the femur in the clamp, attach the tendo Achillis to the writing lever (S), and place the nerve over the electrodes in the ordinary muscle moist chamber. Adjust the moist chamber on its stand, and raise it to a suitable height. Load the lever with 20 grams, and direct its point to the side to which the pendulum swings. The crank myograph may be used. Fix the pendulum with the detent, and adjust the writing-style of the lever on the smoked surface. Connect the secondary spiral either with the muscle directly, or preferably with the electrodes on which its. nerve rests, intro- ducing a short-circuiting key. In fig. 108 this is omitted, and the wires of the secondary circuit go direct to the muscle. After XXXV.] ANALYSIS OF MUSCULAR CONTRACTION. 183 un-short-circuiting, with the hand break the primary circuit to make certain that a contraction occurs on breaking the primary circuit. (d.) See that the trigger-key (K') of the pendulum (in the primary circuit) is closed, and the key in the secondary circuit open. Allow the pen- dulum to swing ; as it does so, it knocks open the key in the primary circuit and breaks the current, thus inducing a shock in the secondary circuit, whereby the mus- cle is stimulated and caused to record its con- traction or muscle-curve on the smoked surface. (e.) Take the Abscissa, i.e., the base line. Rotate the stand on which the moist chamber is sup- ported, so as to withdraw the writing point of the lever from the recording surface. Bring the pen- dulum back to the detent, adjust the writing-style, close the trigger-key, and keep the secondary cir- cuit short-circuited by closing the Du Bois key. Allow the pendulum to swing. This records the abscissa or base line. (/) Ascertain the latent period as follows : — Bring the pen- dulum to the detent, short-circuit the secondary current, and withdraw the writing-style as in (e.). Close the trigger-key of the pendulum, and with a finger of the left hand keep it closed. Allow the lever to touch the glass plate in its original position, and with the right hand bring the knife-edge of the pendulum in contact with the trigger-key, so as just to open it. Thus a vertical line is inscribed on the stationary plate, which indicates the moment of stimulation. (g.) Remove the muscle lever, place the pendulum in the detent, close the trigger-key, take a tuning-fork, vibrating, say, 120 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 Fig. 108. — Scheme of the Arrangement of the Pen- dulum. B. Battery ; /. Primary, II. Secondary spiral of the induction machine; S. Tooth; K. Key ; C. C. Catches ; K in the corner. Scheme of K : K. Key in primary circuit. It is well to have a short-circuiting key in the secondary circuit. 1 84 PRACTICAL PHYSIOLOGY. [XXXV. it. Allow the pendulum to swing, when the vibrating tuning- fork will record the time-curve under the muscle-curve (fig. 109, 250 DY). All the conditions must be exactly the same as when the muscle-curve was taken. (h.) Remove the paper, varnish the tracing, hang it up to dry, 250 DV. FIG. 109.— Pendulum Myograph-Curve. 8. Point of stimulation ; A. Latent period ; B. Period of shortening, and C. of relaxation. and next day measure the tracing. Bring ordinates vertical, a', b', c', to the abscissa, and measure the "latent period" (fig. 109 A), the duration of the shortening (B), the phase of relaxation (C), and the contraction remainder. Fig. i 10.— Spring-Myograph. 2. Spring-Myograph (fig. no). — The arrangements are exactly the same as for the pendulum-myograph, the trigger-key of the myograph being placed in the primary circuit. The instrument must be raised on blocks. XXXV.] ANALYSIS OF MUSCULAR CONTRACTION. AaA/\A/VA_ (a.) Cover the slip of glass with glazed paper, smoke it, and fix it in the frame. Push the plate to one side by means of the rod attached to it, and fix it by means of the catch. Close the trigger-key (h), and introduce it into the pri- mary circuit of the induction machine. (6.) Make a nerve-muscle preparation, and arrange it to write on the glass plate as directed in 1 (c). Remember to un-short -circuit the secon- dary circuit. (c.) Press on the thumb- plate (a), thus liberating the spring, when the glass plate moves swiftly to the other side, and in doing so the tooth (d) on its under surface breaks the primary circuit, and the muscle-curve is recorded. (d.) Short-circuit the secon- dary circuit, push back the glass plate, and fix it with the catch ; close the trigger-key, and shoot the glass plate again horizontal line. (e. ) Remove the moist chamber and take the time-curve. Push the glass plate back again, and secure it by the catch ; close the trigger-key — in order that the conditions may be exactly the same Fig. hi.— Arrangement for Estimating the Time-Relations of a Single Muscular Con- traction. B. Battery ; A'. Key in primary circuit ; /. Primary, II. Secondary spiral, without a short-circuiting key ; I. Muscle lever ; e. Electro-magnet in primary cir- cuit ; t. electric signal ; St. Support ; AC. Revolving cylinder. Introduce a short- circuiting key into the secondary circuit. This records the abscissa or FIG. ii2.— Time-Marker. L. Lever; B. Electro-magnet bobbins; S. Support; W, W. Wires. as before — strike a tuning-fork, vibrating, say, 120 double vibra- tions per second, and when it is vibrating adjust its writing- style under the abscissa. Shoot the glass plate again, and the time- curve will be recorded. 1 86 PRACTICAL PHYSIOLOGY. [XXXV. (/.) Remove the tracing, fix it and measure it out, determining the length of the latent period and the duration of the contrac- tion, and of its several parts. 3. Study the improved form of this instrument recently introduced by Du Bois, in which the glass plate is set free, and the tuning-fork vibrations are recorded simultaneously when a handle is pressed. It has a simple mechanism for adjusting the writing-styles for the muscle and abscissa. Fig. —Signal and Vibrating Tuning-Fork in an Electric Circuit. D. Drum ; C. Signal ; EM. Electric tuning-fork ; Pt. Platinum contact. 4. On a Revolving Cylinder. (a.) Arrange the drum to move at the fastest speed. (b.) Arrange an induction machine for single shocks, the secondary circuit to be short-circuited, and arranged to stimu- FIG. 114. -Deprez Electric Signal or Chronograph, as made by the Cambridge Scientific Instrument Company. late a nerve attached to a muscle placed in a moist chamber, as directed for the foregoing experiments. Into the primary circuit XXXV.] ANALYSIS OF MUSCULAR CONTRACTION. I87 introduce, besides the Morse key, an electro-magnet with a mark- ing lever (figs. 104, 111, e), and cause its point to write exactly under the muscle lever. Arrange, with its point exactly under the other two, a Deprez chronograph or signal, in circuit with a Von Fig. 113.— Electro-Magnetic Signal of Marcel Deprez, as modified and made by C. Verdiu. tuning-fork of known rate of vibration, and driven by means of a battery (fig. 113). The three recording levers are all fixed on the same stand, which should preferably be a tangent one, i.e., the rod bearing the recording styles can by means of a handle be made to rotate Fig. 116. — Chronograph arranged to Write on a Horizontal Cylinder, as made by Verdin. so as to bring the writing-styles in contact with the recording surface. This avoids the overlapping of the time-curve which otherwise happens. On un-short-circuiting the secondary circuit and breaking the primary one, the muscle contracts, and at the same time the stvle of the electro-magnet is attracted and records the exact moment of stimulation (fig. 104). i88 PRACTICAL PHYSIOLOGY. [XXXV. 5. Time-Recorder (fig. 112). — This is merely an electro-magnet introduced into an electric circuit, and the magnet (B) is so arranged as to attract a writing-style (L). The drum may move on a vertical (fig. 112) or on a horizontal axis (fig. 116). 6. Deprez Signal (figs. 113, 114, 115).— This small electro- magnet has so little inertia, *hat, if it be introduced into an electric circuit, its armature, which is provided with a very light writing point, vibrates simultaneously with the vibrations of an electric tuning-fork introduced into the same circuit. Arrange the signal and tuning-fork as in fig. 113. The«drum must move more rapidly, the more rapid the vibrations of the tuning-fork used. ADDITIONAL EXEKCISES. 7. Vibrating Reed as a Chronograph. — For measuring small intervals of time this is very convenient. The arrangement was first adopted by Gruumach, FIG. 117.— Marey's Simple Myograph, as made by Verdin. acting on the suggestion of Kronecker. A steel tongue, vibrating a hundred tunes per second, covers an oblong aperture placed at the lower part of a XXXV.] ANALYSIS OF MUSCULAR CONTRACTION. 189 gradually-narrowing brass tube, closed at the narrow end. To the tongue is attached a stylette, which records the movements of the former. To 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 appa- ratus, the retd (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. 8. Simple Direct Myograph of Marey (fie. 117) — In this form of myograph the frog is pinned on a cork plate, the tendon of the gastrocnemius is dissected out and attached to a writing-lever, which is weighted with a counterpoise ; 1 90 PRACTICAL PHYSIOLOGY. [XXXVI. the 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 situ, and is under more normal conditions than in the case of an excised muscle, e.g., the circulation in the muscle is still carried on. It is very useful for the study of the action of poisons on muscle. 9. Spring Myograph of Fredericq (fig. 118). — This 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 short pin attached to the frame carry- ing the glass plate when the plate is discharged. In an improved form of the instrument, a steel rod made to vibrate at the moment the plate is discharged records a time-curve beside the muscle-curve. LESSON XXXVI. INFLUENCE OF TEMPERATURE, LOAD, AND VERATRIA ON MUSCULAR CONTRACTION. 1. Influence of Temperature on Muscular Contraction. (a.) Arrange the experiment with a crank-myograph as in Lesson XXXI Y. 10, but do not remove the skin of the leg. Take a tracing at the normal temperature. (b.) Alter the height of the drum or that of the myograph. Place ice upon the skin over the gastrocnemius for some time, FlOi iiq.— Showing how the Form of a Muscle-Curve Varies with the Temperature of the Water Mowing through the Box, shown in fig. 107. 1 at 50 C; 2 at 10° ; 3 at 15°; 4 at 200 ; 5 at 250 ; 6 at 30° ; 7 at 350 ; and 8 at 400 C. The lowest tracing indicates time, 100 D.V. per second, x the moment of stimulation. and then take another tracing, noting the differences in the result, the contraction being much longer. (c.) Adjust a piece of wire gauze over the leg, and allow it to project beyond the end of the plate of the myograph. Heat the gauze with a spirit-lamp. Take a tracing. The contraction is shorter than in 1 (b.). Do not overheat the muscle. XXXVI.] INFLUENCE OF TEMPERATURE, ETC. IQI (d.) A piece of lead-piping of narrow diameter (| inch) can be bent into the form of a cylinder, and the muscle placed within it. Water of various temperatures can then be passed through it. (e.) The muscle may be attached to an ordinary horizontal writing-lever. Surround the muscle with a double-walled box, with an inflow and outflow tube, through which water at different temperatures can be passed. A delicate thermometer is placed in the chamber with the muscle. (/) Perhaps for the purpose of the student the most convenient method is to allow the muscle to rest on a small circular brass box, fitted into the wooden plate of the crank-myograph. The box (B, B) is provided with an inflow and an outflow tube, through which water of the desired temperature can be passed (fig. 107). 2. Influence of the Load on the Form of the Curve. (a.) Arrange an experiment with the pendulum-myograph as in Lesson XXXV. 1, using either a muscle-lever or a crank- myograph. (6.) Take a tracing with the muscle weighted with the lever only. (c.) Then load the lever successively with different weights IgSZ- on( 250 DV. Fig. 120.— Pendulum-Myograph Curves, showing the Influence of the Load on the Form of the Curve. (5 ... 20 ... 50 ... 70 ... 100 grams), and in each case record a curve and observe how the form of the curve varies (tig. 120). (d.) In each case record the abscissa and time-curve with the usual precautions. 3. Influence of Veratria on Contraction. (a.) Destroy the brain of a frog, and inject into the ventral lymph sac 10 minims of a freshly -prepared o. 1 per cent, solution of veratria. (b.) Arrange the induction machine for single shocks. (c.) Make a nerve-muscle preparation, fix it in a moist chamber, 192 PRACTICAL PHYSIOLOGY. [XXXVII. and arrange the muscle-lever to record its movements on a slowly revolving drum. Take a tracing, observing the long drawn-out form of a curve, and how long the muscle takes to relax. Tig. i2i.— Veratria Curve (Upper). Normal Muscle-Curve (Lower). (d.) The direct action of veratria on muscular tissue may also be studied by the apparatus described in Lesson XL., and by this method it is easy to compare the form of the curve before and after the action of the poison (fig; 1 2 1 )j. (e.) The action of veratria may be studied also by means of Marey's simple myograph (p. 89). LESSON XXXVIL ELASTICITY AND EXTENSIBILITY OP MUSCLE. 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 the writing muscle-lever of the moist chamber, and fix a scale-pan to the lever. Neglect the weight of the pan, and see that the lever writes horizontally on a stationary drum. It is better to do the experiment with the sartorius, as it has parallel fibres. (6.) Place in the scale-pan, successively, different weights (10, 20, 30, 40 ... 100 grams). On placing in 10 grams, the lever will descend ; remove the weight and the lever will ascend. Move the drum a certain distance, 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 nevertheless the muscle-lever will rise to its original height on removing the weight. Repeat this with other weights. With the heavier weights care must be taken that everything is securely clamped. If the apices of all the lines obtained be joined, they form &hyper- XXXVII.] ELASTICITY AMD EXTENSIBILITY OF MUSCLE. 193 Fig. 122.— Curve of Elasticity of a Frog's Muscle. Fig. 123. —Curve of Elasticity of India-rubber. bola. 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 suid to be very perfect. The hyper- bola obtained shows further- that the increase in length is not directly proportional to the weight, but it diminishes as the weights increase (fig. 122). (c.) Repeat the same observa- tion with a thin strip of india- rubber. In this case equal incre- ments of weight give an equal elongation, so that a line join- ing the apices of the vertical lines drawn after each weight is a straight line (fig. 123). 2. The Extensibility of Muscle is Increased during Contrac- tion, its Elasticity is Diminished. (a.) Arrange a muscle in a moist chamber, connecting it to a lever to record on a drum, and adjust an interrupted current to stimulate the muscle, either directly or indirectly. (b.) Load the lever with 50 grams, and in doing so allow the drum to move slowly. Remove the load and observe the curve obtained. (c.) 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 with the drum stationary, and then to record the tracing with the drum in motion. (/.) A better curve is obtained by using a long counterpoised lever attached to the muscle, which writes on a very slow-moving drum. A weight is made to travel along the lever by means of two pulleys with an endless string. ADDITIONAL EXERCISE. 3. Elasticity of an Artery.— Test the elasticity of a strip of aorta in the same way. 194 PRACTICAL PHYSIOLOGY, [XXXVIII. LESSON XXXVIII. FATIGUE OF MUSCLE AND NERVE-ERGOGRAPH. FIG. 124. — Fatigue-Curve. The sciatic nerve was stimu- lated with maximal induction shocks and every fifteenth contraction recorded. 1. Fatigue of Muscle. (a.) Arrange an induction apparatus for single shocks, but introduce into the primary circuit, in addition to the Du Bois key, a trigger-key, the latter fixed to a stand, and so placed that a tooth on the edge of the drum can knock it over, and thus break the primary current as required. Or attach to the edge of the under surface of the drum a short style ; a strong pair of bull- dog forceps clamped on to it does perfectly well. (b.) Make a nerve- muscle preparation, fix the femur in a clamp, and adjust the preparation in the moist chamber or a crank-myograph — the whole to be supported on a tangent stand. Attach the muscle to a writing-lever to record on a revolving drum. (c.) The best plan is to fix a platinum style on the spindle of the drum, and as it revolves it comes in contact with another piece of platinum introduced into the primary circuit, and fixed to the base of the drum-support, so that a break-shock is obtained each time the drum revolves. If a tangent support be used for the muscle-lever, then although the muscle contracts at each revolution of the cylinder, one may record every tenth or fifteenth contraction just as one pleases. (d.) Close the trigger-key, and on allowing the cylinder to revolve, the style knocks it over, breaks the primary circuit, and induces a shock in the secondary. Immediately short-circuit the secondary circuit, close the trigger-key and unshort-circuit the secondary circuit, and allow the drum to revolve. Repeat this until the muscle is fatigued. Record only every fifteenth contraction. In this way the muscle is always stimulated at the same moment, and the various curves are superposed and can be readily compared (fig. 124). XXXVIII] FATIGUE OF MUSCLE AND NERVE. 195 (e.) Observe how rapidly the height of the curves falls, while their duration is longer. In nearly every case fatigue-curves from muscle show a " staircase " character (fig. 126), the second curve being higher than the first one, and the third than the second. ADDITIONAL EXERCISES. 2. Instead of recording on a moving surface, a stationary one may be used (or a very slow-moving drum. I mm. per sec), either a drum or a flat glass surface, while the muscle may be attached to a crank-myograph or to Pfliiger's myograph (fig. 125). (a.) Arrange the experiment as before, but adjust the muscle in a myograph, the primary circuit being still broken by a revolving drum. {b.) When the muscle contracts, it merely makes a slightly curved scratch FlQ. 125.— Pfliiger's Myograph. K. Clamp ; M. Muscle ; W. Weight in scale-pan ; F. Writing-style ; P. Counterpoise of lever ; SS. Supports. on the drum. Move the plate with the hand a little distance after each con- traction. A series of nearly vertical lines is obtained. (c.) Study the form of the curve obtained. Note the " staircase " character of the first few beats, and then the gradual decline of the height of the con- tractions. 3. Fatigue -Curve. — Use a very 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. In this way a curve such as fig. 126 is obtained. Note the "staircase" character of the curve, i.e., the second contraction is higher than the first, the third than the second, and so ig6 PRACTICAL PHYSIOLOGY. [XXXVIII. on for a certain number of contractions. After that the height of the contrac • tion falls steadily, so that a line uniting the apices of all the contractions forms a straight line. 4. Mosso's Ergograph. — This is a most useful instrument, by means of which the student can study the process of fatigue on himself, the conditions that predispose to it, and the process of recovery, as well as the effect of various conditions on the fatigue-curve. By means of this instrument also the amount of work done is recorded graphically. 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 slightly prone 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 apparatus, and to the latter is added a load of known weight — e.g., 2-3 kilos. The experimenter flexes the middle finger, lifts the load, and as soon as the contraction is over the load extends the 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 minute. Fig. 126. — l'atigue-(Jurve of a .Frog's Muscle recorded on a very Slow-moving Drum. 5. Seat of Exhaustion in Nerve and Muscle. A. (a.) Arrange an induction machine for interrupted shocks. Connect the secondary coil with a Pohl's commutator without cross-bars. (6.) Arrange a Daniell's cell connected to N.P. electrodes, and short-cir- cuited for a constant current — the "polarising current" (Lesson XLI. 2). (c.) 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. 102). Lay both nerves over a pair of Du Bois electrodes. Arrange a glass shade, lined in part with moist blotting-paper to cover them and keep them moist. (cl. ) Attach the electrode wires to two of the binding screws of the commu- tator, turning the handle, so that the current can be passed through both nerves when desired. (e. ) Arrange the nerve of B on the N.P. electrodes placed between the tetanising current and the muscle, so that the - pole is next the muscle. Pass an interrupted current through both nerves ; A will become tetanic while B remains quiescent ; the impulse cannot pass because of the effect of the " polarising current " producing electrotonus. XXXIX.] TETANUS. 197 (/.) Continue to stimulate until the tetanus in A ceases. Break the polar- ising current ; B becomes tetanic. As both nerves have been equally stimulated, both are equally fatigued. As B becomes tetanic, the seat of the fatigue is not in the nerve-trunk. B. (a.) Arrange an induction coil and commutator as before. (b.) Prepare a nerve-muscle preparation, with a straw flag as before, and place its nerve over the Du Bois electrodes attached to the commutator. Pass two fine wires through the gastrocnemius and attach them to the other two binding screws of the commutator. (c.) Tetanise the nerve until the tetanus ceases. Then reverse the commu- tator and stimulate the muscle. It contracts. Therefore, in this case, the seat of fatkrue is not in the muscle. LESSON XXXIX. PRODUCTION OF TETANUS-METRONOME THICKENING OP A MUSCLE. 1. Production of Tetanus. — The tetanising current may be made and broken with the hand, by Neef s hammer, or by means of a vibrating rod. Apparatus. — Daniell's cell, five wires, flat spring, cup of mercury in a wooden stand, induction machine, Du Bois key, moist chamber and muscle-lever, recording drum moving at a medium speed. (a.) Arrange the experiment as in fig. 127; the induction machine for single shocks, short-circuiting the secondary circuit. Fig. 127.— Scheme of Arrangement for Tetanus. VS. Vibrating spring; J/. Cup for mercury. Other letters as before. Place in the primary circuit the flat metallic spring, held in a wooden clamp. One end of the spring has a needle fixed at right angles to it, which dips into a cup of mercury fixed in a wooden stand. The needle hangs just above the mercury cup 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 machine. Cover the mercury with alcohol and water (1 13), to prevent oxidation, and to keep the resistance more uniform. 198 PRACTICAL PHYSIOLOGY. [XXXIS. (h.) Make a nerve-muscle preparation, place it in a moist chamber, attach to it a writing-lever, weight the latter with 15 grams, and cause it to write on a drum revolving at a moderate rate. (c.) 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, Fig. 128. — Curves Obtained in Previous Experiment, the last almost a Complete Tetanus. and before the spring ceases to vibrate short-circuit the secondary current. (d.) Shorten the vibrating spring somewhat, and repeat the same experiment, making the tracing follow the previous one. (e.) Make several more tracings, always shortening the spring, until the tracing no longer shows any undulations, until the spasms are completely fused, i.e., until it has passed from the phase of " incomplete " to " complete tetanus." Fig. 129.— Interrupter for Tetanus. W. Wooden block; YS- Vibrating spring; BS and BS'. Binding screws ; C. Movable clamp ; C". Clamp to fix spring ; M. Cup of mer- cury. (/.) Finally take a tetanus-curve by introducing Neef's hammer instead of the vibrating flat spring. (g.) Study the tracings. At first the tracings will be indented, but gradually there will be more and more fusion of the teeth, until a curve unbroken by depressions is obtained. In the curve XXXIX.] TETANUS. 199 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. When the current is shut off the descent is very steep at first, and towards the end very slow. 2. Instead of using the spring held in a clamp, a convenient form is shown in fig. 129. If desired the spring can be kept vibrating by an electro- magnet. ADDITIONAL EXERCISES. 3. Interruption by a Metronome. — Instead of the vibrating rod or Neef's hammer, introduce into the primary circuit a metronome (fig. 130), provided Fro. 130. — Metronome. with a wire which dips into a mercury cup introduced into the primary circuit. Vary the rate of vibration of the metronome, and observe the effect on the muscle-curve. Fig. 131- -Magnetic Interrupter with Tuning-Fork, as made by the Cambridge Scientific Instrument Company. 4. Magnetic Interrupting Tuning-Fork.— Instead of a vibrating spring, the primary current may be interrupted by means of a tuning-fork of known rate 200 PRACTICAL PHYSIOLOGY. [XXXIX. of vibration, and kept in motion by means of an electro-magnet. The instru- ment (fig. 131) 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 FIG. 132. — Marey's Registering Tambour. Metallic Capsule, T, with thin india-rubber stretched over it, and bearing an aluminium disc, which acts upon the writing lever, H. mercury placed in a small cup, the primary current is made and broken. One of the most important points in connection with the use of this instrument is Fig. 133. — Marey's Registering Tambour. The writing-lever is represented as cut short. to keep the surface of the mercury clean and bright. This is necessary in order to have the successive shocks of equal intensity. Kronecker has devised such an apparatus. The vibrating rod is so adjusted that stimuli from 1 to 50 or 60 per second can be obtained therewith. 5. Thickening of a Muscle during Contraction. (a.) Arrange a Marey's tambour to write on a pendulum-myograph (figs. 132, 133). (b.) Fix Marey's pince myographique (fig. 133) 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 plate-like electrodes are fitted and connected with binding screws. Keep the handles of the bellows pressed upon the adductor muscles by means of an elastic band. Connect the re- ceiving tambour of the pince or the nozzle of the bellow's with the recording tambour, introducing a valve or T-tube with a FlG. 134.— Marey's Pince Myo- graphique, as made by Ver- din. XL.] SUCCESSIVE SHOCKS. 201 screw clamp into the connecting elastic tube, to regulate the pressure of air within the system of tubes. (c.) Arrange an induction machine with the trigger-key of the pendulum- myograph in the primary circuit, and the pince or bellows in the secondary. Take a tracing in the ordinary way. The time relations of the contraction are determined in the manner already stated (Lesson XXXV.). LESSON XL. TWO SUCCESSIVE SHOCKS-ACTION OP DRUGS ON EXCISED MUSCLE. 1. Two Successive Shocks. — The primary current may be broken by means of a revolving drum. To the spindle of the drum is fixed a projecting rod with a fine platinum contact. As the drum rotates, the platinum wire completes the primary circuit hj touching another platinum wire fixed to a vertical rod attached to the frame of the drum itself. The vertical rod is insulated from the iron framework. This eives one shock. Near the Fig. 135. — Effects of Two Successive Shocks on a Muscle. 1. 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. platinum wire fixed to the drum-frame is another similar contact, so that this gives a second contact. The distance between these two wires, i.e., the means for successive contacts, and the rapidity of rotation of the cylinder, enables one to adjust the experiment so as to throw in the second shock at any period after the appli- cation of the first shock. 202 PRACTICAL PHYSIOLOGY. [XL. Fig. 135 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. ADDITIONAL EXERCISES. 2. 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 upper end is open (fig. 136, B). A wire connected with a key (K') short-circuiting the secondary coil of an induction machine perforates the cork. Arranged above is a light lever (L) provided with an after-load {al), and moving on an axis, the short arm projecting over the mouth of the jar. The whole arrangement is fixed to a platform (P), with an adjustable stand (S) bearing the fulcrum of the lever and the after-load. The cork must be renewed with each new drug used. (a.) Dissect out the gastrocnemius, divide the femur with the gastrocnemius attached just above the attachment of the latter, and the tibia below the knee- FlG. 136.— Wild's Apparatus for Studying the Action of Poisons on Muscle. D. Drum; P. Platform ; S. Stand ; al. after-load ; L. Lever ; B. Bottle with muscle ; K'. Key. joint. Pass a fine metallic hook through the knee-joint 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. (6.) Fill the glass cylinder — which encloses the muscle — with normal saline. Stimulate the muscle directly with break shocks, and take a tracing. (c.) Remove the normal saline with a pipette, and replace it with a solution of the drug whose action you wish to study — e.g., veratria I in 5000, or barium chloride I in 1000. Study the veratria tracing (fig. 121). 3. Two Successive Shocks (another method). — Use the pendulum- or spring-myograph or a revolving cylinder, preferably the last. The pendulum- and spring-myographs used must be provided with two trigger-keys which are capable of being adjusted at any required distance from each other, and opened by the moving recording plate of the instrument. XLL] ELECTRO-MOTIVE PHENOMENA. 203 (a.) Charge four Daniell cells, and connect two with one induction machine and two with another, introducing one trigger-key in the primary circuit of one induction machine, and the other trigger-key in the primary circuit of the other one. If the pendulum-myograph be used, let the trigyer-keys be about 5-8 centimetres apart. Connect the two secondary coils by a wire stretching between the two adjacent terminals. The other two terminals are connected with a short-circuiting Du Bois key, from which the electrodes proceed. (b.) Arrange a muscle or nerve-muscle preparation either in a moist chamber or on a crank myograph ; place the electrodes under the nerve or stimulate the muscle directly. (c.) Take a tracing in the ordinary way, after unshort-circuiting the secon- dary coils, and seeing that both primary circuits are closed. On discharging the instrument, first the one key and then the other is opened. It is necessary to ascertain beforehand that both break shocks are nearly of the same inten- sity. Take a series of tracings, gradually diminishing the distance between the two trigger-keys. In each case record the movement of stimulation with each trigger-key. LESSON XLI. DIFFERENTIAL ASTATIC GALVANOMETER— NON- POLARISABLE ELECTRODES-SHUNT-DEMAR- CATION AND ACTION CURRENTS IN MUSCLE. ELECTRO-MOTIVE PHENOMENA OF MUSCLE AND NERVE. 1. Thomson's High-Resistance Differential Astatic Galvano- meter. (a.) Place the galvanometer (fig. 137) upon a stand where it is unaffected by vibrations, e.g., on a slate slab fixed into the wall at a suitable height, or on a solid stone pillar fixed in the earth, taking care that no iron is near. (b.) Place the galvanometer so that it faces west, i.e., with the plane of the coils in the magnetic meridian, the magnetic meridian being ascertained by means of a magnetic needle. As the galva- nometer is a differential one, to convert it into a single one, con- nect the two central binding screws on the ebonite base by means of a copper wire. (c.) By means of the three screws attached to the ebonite base level the galvanometer. (d.) Allow the mirror attached to the upper needle to swing freely. Take off the glass cover and steadily raise the small milled head on the top of the upper coils, which frees the mirror. Replace the glass shade. (e.) Place the scale (fig. 138) also in the magnetic meridian and 1 metre from the mirror, taking care that it is at the proper 204 PRACTICAL PHYSIOLOGY. [XLI. height. An improved form of scale with several adjustments has recently been introduced. Instead of a mere slit in the 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. FIG. 138.— Lamp and Scale for Thom- son's Galvanometer. Fid. 137.— Sir William Thomson's Re- flecting Galvanometer, u. Upper, I. Lower coil ; s, s. Levelling screws ; m. Magnet on a hrass support, b. Fig. 139. — Kon- Polarisable Elec- trodes. Z. Zincs ; K. Cork ; a. Zinc sulphate solu- tion ; t, t. Clay points. (/.) Light the paraffin lamp, 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 light is thrown on the mirror in order to obtain a good image on the scale. The lamp used is an ordinary paraffin one provided with a copper chimney with a plane glass in front and a concave mirror behind. When lighted, the edge of the flame is turned toward the slit. XLL] ELECTRO- MOTIVE PHENOMENA. 205 (g.) Make the needle all but astatic by means of the magnet attached to the bar above the instrument. The needle is most sensitive when it swings sloioly. (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 off the scale. 2. To Make Non-Polarisable Electrodes. — One may use the old form as invented by Du Bois-Revmond, the simple tube elec- trodes, or the " brush electrodes " of V. Fleischl (fig. 142). (a.) Use glass tubes about 4 cm. long and 5 mm. in diameter, tapering somewhat near one end, and see that they are perfectly clean. (b.) 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 wood or thin glass rod to do so ; allow part of the clay to project beyond the tapered end of the tube (fig. 139, t, t). (c.) By means of a perfectly clean pipette half fill the remainder of the tube with a saturated neutral solution of zinc sulphate. Make t/co such electrodes. (d.) Into each tube introduce a well-amalgamated short 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 in the plate or stage of the moist chamber. Be careful that the zinc does not touch the clay. 3. The Shunt. — This is an arrangement by which a greater or less proportion of a current can be sent through the galvanometer (fig. 140). The brass bars on the upper surface are marked with the numbers -*-, ~-^, ^y, indicat- ing the ratio between their resistance and that of the galvanometer, so that when the plug is inserted in positions afterwards to Fig. 140.— The Shunt be mentioned, there may be -^ T J^, or y^Vo" of the whole current sent through the galvanometer 4. Demarcation-Current of Muscle. (a.) Arrange the apparatus according to the scheme (fig. 141). (b.) Introduce a shunt between the N.P. electrodes and the galvanometer. Connect two wires from the electrodes to the 206 PRACTICAL PHYSIOLOGY. [XLI. binding screws (A and B) of the shunt, and from the same bind- ing screws attach two wires of the same kind to the galvanometer. Insert a plug (C) between A and B, whereby the muscle-current is short-circuited. When working with muscle, keep a plug in the hole opposite -g- on the shunt. Arrange the lamp and scale so as to have a good image of 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. 141, m). (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 all the plugs 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. FIG. 141.— Arrangement of Apparatus for the Demarcation-Current of Muscle. M. Muscle on a glass plate, P ; S. Shunt ; G. Galvanometer ; Mg. Its magnet moved by the milled head, m ; L. and Sc. Lamp and scale. (d.) 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 (1 : 20) and two wires of zinc ( - ) and copper ( + ), with wires soldered to them. Connect them with the galvanometer. Arrange the shunt so that t^q or yoVo part of the current thus generated goes through the galvanometer. Note the deflection and its direction. Arrange the N.P. elec- trodes 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; these are selected, because they XLI.J ELECTRO-MOTIVE PHENOMENA. 20J 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 with the N.P. electrodes. (/.) Keep one plug in the shunt at C, so as to short-circuit the electrodes, and the other plug at ^. Cut a fresh transverse sec- tion at one end of the muscle, and adjust the point of one elec- trode 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. 141). (g.) Current of Rest. — Remove the short-circuiting plug C from the shunt, keep one plug in at -g-, so that —^ of the total current from the muscle goes through the galvanometer. Note the direc- tion and extent of the deflection. By noting the direction, and from the observation already made (d), one knows that the longi- tudinal surface of the muscle is + , 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 rest, and it flows from the equator or middle of the muscle towards the cut ends. It is also called the demarcation-current. (h.) Bring the N.P. electrode on the longitudinal surface nearer to the end of the muscle, and note the diminution of the deflection of the needle. Replace plug C. (i.) Vary the position of the electrodes and note the variation in the deflection. If they be equidistant 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 electromotive force, diminishes as the elec- trodes are moved from the equator or the centre of the transverse section. In certain positions no deflection is obtained. 5. Action-Current of Muscle. (a.) Use the same muscle preparation, or isolate the gastroc- nemius with the sciatic nerve attached. Divide the muscle trans- versely, and lay the artificial transverse section on one electrode, and the longitudinal surface on the other. Observe the extent of the deflection. (b.) Adjust a Du Bois induction apparatus for interrupted shocks, placing it at some distance from the galvanometer. (c.) Take the demarcation-current (current of rest), observing the deflection, and allow the spot of light to take up its new position on the scale. Stimulate the muscle by the ordinary electrodes to throw it into tetanus, and observe that the spot of light travels towards zero. This was formerly called the "negative 208 PRACTICAL PHYSIOLOGY, [XLI. variation of the muscle current." It flows in an opposite direc- tion to the current of rest. It is now called the " action-current " of muscle. If the gastrocnemius be used, stimulate the sciatic nerve. Care must be taken that the muscle does not shift its posi- tion on the electrodes. ADDITIONAL EXERCISES. 6. The Brush Electrodes of V. Fleischl are very convenient (tig. 142). They consist of glass tubes 5 mm. in 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 mix- ture of kaolin and nor- mal saline. Fig. 142.— Brush Electrodes of V. Fleischl. 7. D'Arsonval's Non - Polarisable Electrodes (tig. 143). — 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 part is placed in a tube tapering to a point below and filled with normal saline. At the lower tapered end there is a small aper- ture. The tube is closed above with a cork (C), through which passes the silver electrode (A). The tapered points are brought into contact with the tissues. XLII.] X Ell YE- CURRENTS. 209 LESSON XLII. NERVE - CURRENTS — ELECTRO - MOTIVE PHENO- MENA OP THE HEART-CAPILLARY ELECTRO- METER. Zn 1. Demarcation- Current of Nerve (Current of Rest). (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. (b.) Prepare N.P. electrodes for a nerve. In this case the electrodes are hook-shaped, and one is adjusted over the other. The upper hooked electrode has a groove on its concavity communicating with the interior of the tube (tig. 144). Place only one plug 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 upper N.P. electrode (N), and resting with its two cut ends on the lower electrode (C), thus doubling the strength of the current (fig. 144). (d.) Remove the plug from C in the shunt and pass the whole of the demarcation nerve-current through the galvanometer, noting the deflection. (e.) Instead of adjusting the 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 (l.e). Stimu- late with an interrupted current the free end of the nerve, and observe that the spot of light travels towards zero. This was formerly called the " negative varia- tion " of the nerve-current. 3. Electro-Motive Phenomena of the Heart. — The fig. 144. — Nerve x.P arrangement of the apparatus is precisely the same as Electrodes. X. Nerve in Lesson XLI. (a.) Make a Stannius preparation of the heart, using only the first ligature (Lesson L. 1) to arrest the heart's action. Lead off with brush X.P. electrodes from base and apex of the heart ; there is no deflection. (b.) Pinch the apex so as to injure it ; it becomes negative. (c.) Excise a heart so as to get a spontaneously beating ventricle ; lead off from the base and apex of the latter ; observe the so-called '"negative varia- tion " with each contraction. 4. Capillary Electrometer. (a.) Lead off a muscle to the two binding screws of a capillary electro- meter. The fine thread of mercury must be observed with a microscope. By means of the capillary electrometer Waller lias shown the diphasic varia- tion of the heart-current in man and in a living dog. 0 0. Clay of electrodes ; Zn. Zincs. 210 PEACTICAL PHYSIOLOGY. [XLIII. LESSON XLIII. GALVANI'S EXPERIMENT - SECONDARY CON- TRACTION AND TETANUS — PARADOXICAL CONTRACTION-KUHNE'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 all the viscera. Remove the skin from the hind-legs, divide the iliac bones and urostyle, taking care to avoid injuring the lumbar plexus, which will remain as the only tissue connect- ing the lower end of the vertebral column with the legs. Thrust an S-shaped copper hook through the lower end of the spine and spinal cord (fig. 145). (b.) Suspend the frog by means of the hook to an ordinary iron tripod. Tilt the tripod so that the legs of the frog come in contact with one of the legs of the tripod ; vigorous contractions occur whenever the frog's legs touch the tripod. (c.) Allow the frog to hang perpen- dicularly without touching the tripod, and take 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. 2. Contraction without Metals. — Take a strong frog, make a 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 moistened with normal saline, and allow it to fall upon the gastrocnemius, when the muscle will contract. Contraction occurs because the Fig. 145.— Galvani's Experiment. XLIII] GALVANI S EXPERIMENT. 211 Fig. 146. — Secondary Contraction. nerve is suddenly stimulated, owing to the surface of the muscle having different potentials. 3. Secondary Contraction and Secondary Tetanus. (a. ) Arrange the induction apparatus for single make and break shocks. Pith a frog, dissect out two nerve-muscle preparations, as in fig. 146. (6.) Place the left sciatic nerve (A) over the right gastro- cnemius (B) or thigh muscles, and the right sciatic nerve over the elec- trodes (E). (c.) Stimulate the nerve with single induction shocks, and note that the muscles of both B and A contract. The contraction in A is called a secon- dary contraction. (d. ) Arrange the induction machine for interrupted shocks, and stimulate the nerve at E. B is thrown into tetanus, and so is A simultaneously. This is secondary tetanus. This is a proof of the "action-current" in muscle. The nerve of A is stimulated by the variation of the muscle-current during the contraction of B. (e.) Ligature the nerve of A near the muscle, stimulate the nerve of B ; there should be no contraction of A although B contracts. (/.) Prepare another limb and adjust it in place of A, ligature the nerve of B. On stimu- lating the nerve of B, no contraction takes place either in A or B. 4. Secondary Contraction. (a.) Make a nerve-muscle preparation and place it on a glass plate (B). Dissect out a long stretch of the sciatic nerve of the opposite side (A). Lay 1 cm. of the isolated sciatic nerve (A) on a similar length of the nerve of the nerve-muscle preparation (B) (fig. 147). (6.) 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. (c.) Ligature A and stimulate again. B does not contract. Therefore its contraction was not due to an escape **r— Fig. 147. — Scheme of Secondary Contrac- tion. 212 PRACTICAL PHYSIOLOGY. [XLIII. """^ of the stimulating current. The " secondary contractions " in B are due to the sudden variations of the electro-motivity produced in A when it is stimulated. 5. Paradoxical Contraction. (a.) Arrangement. — Arrange a Daniell's cell and key for giving a galvanic cur- rent. (b.) Pith a frog, expose the sciatic nerve down to the knee (fig. 148, S). Trace the two branches into which it divides. Divide one of the branches as near as possible to the knee, and stimulate its central end (P) by a galvanic current. The muscles sup- plied by the other division of the nerve (T) contract. The second nerve is stimu- lated by the electrotonic alteration of the first. The result does not occur with mechanical or chemical stimulation. FIG. 148.— Scheme of Paradoxical Contrac- tion. ADDITIONAL EXERCISES. 6. Kuhne's Experiment. (a.) Invert an ordinary earthenware bowl (B), and with wax fix to its base a piece of glass 10 cm. square (fig. 149, G). (&.) B,oll two plugs 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. apart. (c.) Make a nerve-mus- cle preparation, lay the muscle on the glass plate, and the nerve over the two rolls of china clay (fig. 149, N). _ (d.) Fill a small glass vessel (C) with normal saline, and allow the two free ends of the clay to dip into it. With each dip the muscle contracts. In this case the nerve is stimu- lated by the completion of the circuit of its own de- marcation current. Fig. 149. — Kuhne's Experiment B. Bowl ; G. Glass plate ; N. Nerve on P, P', Pads of clay ; C. Capsule. 7. Kuhne's Muscle-Press — Secondary Contraction from Muscle to Muscle. — Dissect out the two sartorius muscles of a frog. Place the end of one muscle over the end of the other, both muscles being in line with each XLIV.] ELECTEOTONUS. 2 1 3 other, and the overlapping portion so arranged that they can be pressed together by means of the small screw-press devised by Kiihne for this purpose. _ On stimulating— by electrical, chemical, or other stimuli— the free end of either muscle, so as to cause that muscle to contract, the second muscle also contracts. The negative variation of the muscle-current, or, as it is called by some observers, the action-current, stimulates the second muscle. This result does not take place if a thin layer of tinfoil be placed between the two muscles. 8. Biedermann's Modification of Secondary Muscular Contraction.— If a frog be denuded of its skin and left exposed to the air for twenty-four 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 muscle is made to contract, the other does so secondarily without the use of a muscle-press. LESSON XLIY. ELECTROTONUS-ELECTROTONIC VARIATION OF THE EXCITABILITY. 1. Electrotonus. — When a nerve is traversed by a constant current, its vital properties are altered, i.e., its 'excitability, conductivity, and electromotivity. The region of the nerve affected by the positive pole is said to be in the anelectrotonic, and that by the negative in the kathelectrotonic condition. Therefore we have to study the — I. Electro-motive alteration of the excitability and conduc- tivity. II. Electro-motive alteration of the electromotivity. 2. Electrotonic Variation of the Excitability.— Apparatus Required.— Three Darnell's cells, two pairs of N.P. electrodes, two Du Bois keys, a Morse or spring key, commutator with cross-bars or Thomson's reverser, induction machine, wire, moist chamber, drum, frogs, and the usual instruments. A. (a.) Arrange the apparatus according to the scheme (fig. 150) introduc- ing the Morse key in the primary circuit. Prepare two pairs of N.P. elec- trodes for the nerve. {b.) Take two Daniell's cells and connect them with a Pohl's commutator with cross-bars (C) or Thomson's reverser ; connect the commutator— a short- circuiting key intervening— to one pair of the X.P. electrodes. Call this the "polarising current " (P P). (c.) Arrange an induction machine for tetanising shocks, i.e., introduce Aeef s hammer, the other pair of N.P. electrodes being in the secondary cir- cuit, arranged for short-circuiting. Call this the "exciting current " (E E). (rt.) Make a nerve-muscle preparation with the nerve as long as possible, and arrange it for recording its movements on a drum. Arrange 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 1 centimetre apart. Between 214 PRACTICAL PHYSIOLOGY. [XLIV. the polarising pair and the muscle apply the " exciting " pair of electrodes to the nerve (E E). (e.) With the polarising 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 a little to obtain just a weak contraction, and take a tracing. Previously arrange the commutator to send a descending current through the nerve. While the muscle Fig. 150.— Scheme of Electrotonic Variation of Excitability, and E, E. Stimulation current. P, P. Polarising, is contracting feebly, throw in the descending polarising current ; at once the contraction becomes much stronger. Reverse the commutator to send an ascending polarising current through the nerve, and the contraction will cease. (/.) Repeat the experiment, using Neef's hammer. In the first case, the area stimulated 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 kathelectrotonic condition increases the excitability of a nerve. In the second case, the nerve next the exciting elec- inS A + N e a K a JP Fig. 151.— Scheme of Electrotonic Variation of Excitability in a Nerve. E. Kathode; A. Anode ; N, n. Nerve. The curve above the line indicates increase, and that below the line decrease, of excitability. trodes was in the condition of anelectrotonus, and the contractions ceased ; therefore, the anelectrotonic condition diminishes the excitability of a nerve (fig- 151). B. Another Method. — (a.) Connect two small Grove's cells or two Daniell's to a Pohl's commutator with cross-bars, introducing a Du Bois key to short- circuit the battery. Pill the cups with mercury, and place the commutator XL V.] ELECTROTONIC VARIATION. 215 in a small tray to avoid spilling the mercury. From two of the binding screws connect wires with two X.P. electrodes or the platinum electrodes of Du Bois, introducing a short-circuiting key in the electrode circuit (fig. 152). (b.) Make a nerve-muscle preparation, attach a straw flag to the foot, as directed in Lesson XXX. 4. and clamp the femur in a clamp on a stand, as in fig. 96. 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, i.e., whether the negative or positive pole is next the muscle. (c.) Place a drop of a saturated solution of common salt on the nerve between the electrodes and the muscle. In a minute or less the toes begin to twitch, FIG. 152.— Scheme of Electrotonic Variation of Excitability. D. Drop of strong solution of salt on the nerve, N ; F. Flag on the muscle. and by-and-by all the muscles of the leg become tetanic, so that the flag is raised and kept in the horizontal position. (d.) Turn the commutator so that the positive pole is next the muscle ; at once the straw falls — 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. (e.) Reverse the commutator, so that the negative pole is next the muscle. At once the limb becomes tetanic, the negative pole {kathelectrotonic area) increases the excitability. LESSON XLV. ELECTROTONIC VARIATION OF THE ELECTRO- MOTIVITY — PPLUGER'S LAW OF CONTRAC- TION— HITTER'S TETANUS. 1. The Electrotonic Variation of the Electromotivity. (a.) Arrange a long nerve on the X.P. electrodes, as for determining its demarcation current. Place the free end of the nerve on a pair of X.P. elec- trodes— the polarising current — arranged as in Lesson XL1V. 2, A, so that the current can be made ascending or descending. (b.) Take the deflection of the galvanometer needle or demarcation current when the polarising current is shut off. Throw in a descending polarising current, and observe that the spot of light travels towards zero. Reverse the 2l6 PRACTICAL PHYSIOLOGY. [XLV. commutator and throw in an ascending current, the spot of light shows a greater positive variation than before. From this we conclude that kathelectrotonus diminishes the electromotivity, while anelectrotonus increases it. In the extra- polar kathodic region an electrotonic current appears when the polarising current is closed. It has the same direction as the polarising current. In the anodic region the direction is also that of the polarising current ; but the electrotonic current is stronger than the kathodic current. If a demarcation current exists already, the electrotonic currents are superposed on it. 2. Pfliiger's Law of Contraction. — Apparatus. — Several small Grove's cells, commutator with cross-bars, Du Bois and Morse key, rheochord, N.P. electrodes, moist chamber, wires, frog, recording apparatus, and usual instruments. (a.) Arrange the apparatus as in the scheme (fig. 153). Take two Daniell or small Grove cells, connect them to a Pohl's commutator with cross-bars, and introduce a Morse or mercury key (K) into the circuit ; connect the com- mutator with the rheochord (R). Connect the rheochord with a pair of N.P. electrodes, with a short-circuiting key introduced. Fix to a 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 the slider hard up to the brass blocks. Place the commutator to give an ascending current, E N FIG. 153.— Scheme for Pfliiger's Law. R. Rheochord ; B. Battery ; C. Commutator ; K. Morse key ; K'. Du Bois>ey ; E. N.P. Electrodes ; N. Nerve. make and break the current — gradually adjusting the slider — until a contrac- tion occurs at make and none 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 weak current. Sometimes the current so obtained is not weak enough. The simple rheochord shoidd then be used (p. 153). (c.) Pull the slider farther away and remove one or more plugs until con- traction is obtained at make and break, both with an ascending and descend- ing current. This represents the effect of a medium current. (d.) Use six small Grove's cells, take out all the plugs from the rheochord, and with the current ascending, contraction occurs at break only ; while with 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 will be required to work 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 inter- vals the effect of weak, medium, and strong currents when the current is ascending, and a second preparation to test the results with currents of vary- ing intensity when the current is descending. The results may be tabulated as follows : R = rest ; C = contraction : — XLVL] EXCITABILITY OF NERVE. 217 Ascending. Descending. Strength of Current. On Making. On Breaking. On Making, j On Breaking. Weak c R c R Medium .... c C c C Strong .... R c c R 3. Ritter's Tetanus. (a.) Connect three Darnell's cells with non-polarisable electrodes short- circuiting with a Du Bois key. Prepare a nerve-muscle preparation, and apply 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 five minutes is sufficient), no contraction takes place. Short-circuit, and observe that the muscle becomes tetanic. (6.) 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. LESSON XLYI. UNEQUAL EXCITABILITY AND VELOCITY OF NERVE ENERGY IN A MOTOR NERVE- KUHNE'S GRACILIS EXPERIMENT, ETC. 1. Unequal Excitability of a Nerve. — Apparatus. — Battery, two keys, wires, commutator, induction machine, two pairs of electrodes. (a.) Arrange the apparatus as in fig. 154, introducing a Morse key in the primary circuit. Dissect out the whole length of the sciatic nerve with the foot 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 or piece of caoutchouc will do quite well. (b.) Stimulate the nerve at A with a strength of current that gives just a minimal contraction. Reverse the commutator, and on stimulating at B a much stronger contraction is obtained, because the excitability of a nerve is greater farther from a muscle. Instead of using single shocks, Neef's hammer may be used. 218 PRACTICAL PHYSIOLOGY. [XLVI. 2. Velocity of Nerve-Energy in a Motor Nerve. The rate of propagation of a nerve -impulse may be estimated by either the pendulum- or spring -myograph. With slight modi- fications the two processes are identical, only in using the spring- Fig. 154.— Scheme for the Unequal Excitability of a Nerve. myograph it is necessary to use such a coiled spring as will cause the glass plate to move with sufficient rapidity to give an inter- val long enough for the easy estimation of the latent period. Fig. 155.— Scheme for Estimating the Velocity of Nerve-Energy. (a.) Use the spring-myograph and arrange the experiment according to the scheme (fig. 155), i.e., an induction coil for single shocks with the trigger-key of the myograph (1, 2) arranged in the primary circuit ; in the secondary cir- cuit (which should be short-circuited, not represented in the diagram), place a Pohl's commutator without cross-bars (C). Two pairs of wires from the com- mutator pass to two pairs of electrodes (a, b), movable on a bar within the moist chamber. Measure the distance between the electrodes. XLVL] VELOCITY OF NERVE-ENERGY. 219 (b.) Make a nerve-muscle preparation with the nerve as long as possible (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. (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 and shoot the glass plate. The tooth (3) breaks the primary circuit, and a curve is inscribed on the plate. [d.) Short-circuit again, replace the glass plate, close the trigger-key, reverse the commutator. This time the stimulus will pass through the electrodes away from the muscle (b). Unshort-circuit the secondary circuit, and shoot the glass plate. Again another curve will be inscribed, this time a little later 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. (/.) 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 when the stimulus was thrown into both points of the nerve. (g.) 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 b 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 the impulse to travel from b to a to be r^ sec. Then we have 4 : 100 : ttV : To"> or 3° metres (about 98 feet) per second, as the velocity of nerve- energy along a nerve. 3. Repeat the observation with the penduhim-myograph. Practically the same arrangements are necessary. If it be desired to test the effect of heat or cold on the rapidity of propaga- tion, the nerve must be laid on ebonite electrodes, made in the form of a chamber, and covered with 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. ADDITIONAL EXERCISES. 4. Double Conduction in Nerve— Kuhne's Experiment on the Gracilis. — The gracilis is divided into a larger and smaller portion (L) by a tendinous inscription (K) running across it (fig. 156). The nerve (N) enters at the hilum in the larger half, and bifurcates, giving a branch (A-) to the smaller portion, and another to the larger portion of the muscle. (a.) Excise the gracilis from a large frog, and cut it as shown in fig. 156, 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. The gracilis after excision must be laid on a glass plate with a black background, else one does not see clearly the inscription and the course of the nerves. Both are easily seen on the black surface. 220 PRACTICAL PHYSIOLOGY. [XL VII. (6.) Stimulate the tongue (Z) with fine electrodes about I mm. apart, and contraction occurs in both L and K. This can be due only to centripetal con- duction in a motor nerve, and this experiment is adduced by Kuhne as the best proof of double conduction in nerve fibres. 5. Action of a Constant Current. — In w.uscle and nerve, stimulation occurs only at the kathode when the current is made {closed), and at the anode when it is broken {opened) — ( V. Bezold). This is most readily seen in fatigued muscles. 6. Engelmann's Experiment.— (a.) Suspend vertically a curarised sartorius of a frog, and pass a constant current through its upper extremity. On making the current, the muscle moves towards the side of the kathode, because con- traction occurs at the kathode on making. At break, it inclines to the anode. (h.) Slit up the muscle longitudinally, so that it looks like a pair of trousers, and keep the two legs, as it were, asunder by an insulating medium ; at make, the kathodic Fl at break> the anodic half. the Gracilis. ^ j^hne's Curare Experiment. — (a.) To the margin of a meat-plate fix two copper slips, to serve as attach- ments for the electrodes, and between the copper terminals place a strip of filter-paper moistened with normal saline. {b.) Excise the sartorius of a large frog, and cut it transversely into five or seven pieces of nearly equal length. Place them in their original order on the filter-paper, numbering them I to 5, or I to 7, as the case may be. Pass a feeble tetanising current through the muscle, and note that the central parts, i.e., 2, 3, and 4 (or 3, 4, and 5) contract, while I and 5 (or I, 2, and 6, 7) remain quiescent. On making the current stronger the terminal parts also contract. Why ? Because there are no nerves at the end of the sartorius, and in the first instance the muscular fibres are really excited by stimulation of the intramuscular 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. PHYSIOLOGY OF THE CIRCULATION. LESSON XL VII. THE FROG'S HEART-BEATING OF THE HEART- EFFECT OF HEAT AND COLD -SECTION OF THE HEART. 1. The Heart of the Frog and how to Expose it. (a.) Pith a frog, and lay it on its back on a frog- plate. Make a median incision through the skin over the sternum, and from the middle of this make transverse incisions. XL VII.] THE FROG S HEART. 22 I (b.) Reflect the four flaps of skin, raise the lower end of the sternum 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 transversely to remove part of the anterior body wall. Be careful not to injure the heart. This exposes the heart, still enclosed within its pericardium, where it can be seen beating. (c.) With a fine pair of forceps carefully lift up the thin trans- parent pericardium, cut it open, thus exposing the heart, but be careful not to cut any blood-vessels. 2. Study the General Arrangement of the Frog's Heart. (a.) Observe its shape, noting the two auricles above (fig. 157, Ad, As), and the conical apex of the single ventricle below (r), the auricles being mapped off from the ventricle by a groove Fig. 157. —Frog's Heart from the Front, v. Single ventricle ; Ad, As. Right and left auricles ; B. Bulbus arteriosus ; i. Carotid : 2. Aorta ; 3. Pulmo - cutaneous arte- ries ; C. Carotid gland. FIG. 15S.— Heart of Frog from Behind. s.v. Sinus venosus opened; c.i. In- ferior, c.s.d, c.s s. Right and left superior vena? cavje ; v.p. Pulmonary vein ; A.d, and A.s. Right and left auricles ; A.p. Communication be- tween the right and left auricle. or furrow which runs obliquely across its anterior aspect. The ventricle is continuous anteriorly with the bulbus aortae (B), which projects in front of the right auricle, and divides into two aortas — right and left, the left being the larger (fig. 157). (b.) Tilt up the ventricle and observe the sinus venosus (fig. 158, s.v.), continuous with the right auricle, and formed by the junction of the large inferior vena cava (c.i.) and the two (smaller) superior venae cava? (c.s.s, c.s.d). 3. Observe the order in which the several parts of the heart contract, viz., sinus venosus, auricles, ventricle, and bulbus arteriosus. 222 PRACTICAL PHYSIOLOGY. [XL VII. 4. The Heart Beats after it is Excised. (a.) With a seeker tilt up the apex of the ventricle, and observe that a thin thread of connective tissue, called the "frsenum," containing a small vein, passes from the pericardium to the posterior aspect of the ventricle. Divide it with a fine pair of scissors. Count the number of beats per minute. Seize with forceps the part of the fraenum attached to the ventricle, and lift up the heart therewith ; with a sharp pair of scissors cut out the heart by dividing the inferior vena cava, the two superior venae cavae, and the two aortae. Place the excised heart in a watch- glass, and cover it with another watch-glass. (5.) The heart goes on beating. Count the number of beats per minute. Therefore its beat is automatic, and the heart con- tains within itself the mechanism for originating and keeping up its rhythmical beats. If the heart tends to become dry, moisten it with normal saline solution, although normal saline containing a little blood is better. (c.) Observe also how during diastole the heart is soft and flaccid, and takes the shape of any surface it may rest on, while during systole, when it contracts, it becomes harder, while the apex is raised and erected. 5. Effect of Heat and Cold on the Excised Heart. (a.) Place the watch-glass containing the beating heart on the palm of the hand, and the heart will beat faster ; or place it over a beaker containing warm water, which must not be above 400 C. Observe that as the temperature rises, the heart beats faster — i.e., there are more beats per minute — also that each single beat is faster. (b.) Remove the watch-glass from the palm, place it over a beaker containing cold water or ice, when the number of beats will diminish, each beat being executed more slowly and sluggishly. 6. Section of the Heart. (a.) Expose the heart, divide the pericardium, and tie a ligature round the fraenum, and by means of it raise the heart, and with a curved pair of scissors excise the whole heart, including the sinus venosus, and observe that the heart continues to beat. (b.) Cut off the sinus ; it continues to beat. The rest of the heart ceases to beat for a time, but by-and-by it commences to beat rhythmically. (c.) With a sharp pair of scissors 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.g., by pricking it with a needle. After a distinct latent period, it will execute one — generally XL VII.] THE FROGS HEART. 223 several — beats, and then become quiescent. Stimulate with a single induction shock, this also will cause it to discharge one or more, usually a series of beats. (d.) Cut off the apex of the ventricle; the small conical apex 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.) Expose another heart, and with a sharp pair of scissors divide the ventricle at its upper third just below the auriculo- ventricular groove. Observe that the auricles with the upper third of the ventricle attached to them continue to beat spon- taneously, while the lower two-thirds of the ventricle no longer beats spontaneously. If it be pricked with a needle, however, it contracts just 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 rhythmical contractions. (/.) With a sharp pair of scissors divide the auricles with the attached portion of the ventricle longitudinally. Each half con- tinues to contract spontaneously, although it is possible that the rhythm may not be the same in both. 7. Movements of the Heart. — Expose the heart of a freshly pithed frog as directed in Lesson XL VII. 1, or better still, destroy only the brain and then curarise the frog. After dividing the pericardium and exposing the heart, observe (a.) That the two auricles contract synchronously and force their blood into the ventricle, which, from being pale and flaccid, becomes red, turgid, and distended with blood. (b.) That immediately the ventricle suddenly contracts, and forces the blood into the bulbus aortae, 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 obser- vation will soon satisfy one that this is not the case. Observe very carefully how the position of the auriculo-ventricular groove varies during the several phases of cardiac activity. (c.) 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. (e.) Ligature the fraanum and divide it, tilt up the ventricle by the ligature attached to the frsenurn, and observe the sinus venosus. 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 follows the ven- 224 PRACTICAL PHYSIOLOGY. [XLVIII. tricular systole and that of the bulbus aortse, 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. LESSON XLVIII. GRAPHIC RECORD OF THE PROG'S HEART- BEAT-EFFECT OF TEMPERATURE. 1. Graphic Record of the Contracting Frog's Heart. (a.) Pith a frog, or destroy its brain, then curarise it. Expose the heart, still within its pericardium, and arrange a heart- lever, so that it rests lightly on the pericardium over the beating heart. Adjust the lever to write on a revolving cylinder, mov- ing at a suitable rate (5-6 cm. per second). Take a tracing of the beating of the heart. (b.) A suitable heart-lever is easily made with a straw about 1 2 inches long, or a thin strip of wood about the same length. The lever must be made before commencing the experiment. Thrust a needle transversely either through the straw or wood, Fig. 159.— Simple Frog's Heart-Lever, a. Fulcrum ; L. Glass lever with knob to act as counterpoise ; 6. To fix the apparatus into the cork of a frog-plate ; C. Cork to rest on the heart or through a piece of cork slipped over the straw about two 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 provided with a writing-style of copper- foil, or a writing point made of parchment paper, fixed to it with sealing-wax. By using a long lever a sufficient excursion is obtained. Another form of heart-lever is shown in fig. 159. It consists of a thin glass rod, fixed as shown in the figure. The frog is laid on its back on a frog-plate covered with cork. The XLVIIL] THE FROG S HEART. 225 heart-lever is fixed into the cork by means of the two pins (o>), while c is so adjusted as 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 well to put some resistant body behind the heart. Raise up the ven- tricle, ligature the frsenum, and divide the latter outside the ligature, and behind the heart place a pad of blotting- paper moistened with normal saline, or a thin cover slip. Adjust the lever, with its cork pad, on the junction of the auricles and ventricle, to write on the cylinder, moving at a slow rate (5-6 cm. per second), and take a tracing, noting the rise and fall of the lever (fig. 160). (d.) Fix the tracing, and observe in the tracing a first ascent, due to the auricular contraction, and suceeeling this a second Fig. 160. — Tracing taken with a Frog's Heart- Lever resting on the Auriculo-ventricular Groove. A. Is the heart tracing ; T. Time; each interval represents one second. Fig. 161.— Electric Time-Marker, as made by the Cambridge Scientific Instrument Company. 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. 2. Auricular Contraction. — Adjust the lever again so that it rests on the auricles alone, and take a tracing. Note the smaller excursion of the lever. In this case the cork resting on the auricles must be small. 226 PRACTICAL PHYSIOLOGY. [XLVIII. 3. Ventricular Contraction. — Adjust the lever so as to obtain a tracing of the ventricular movements only. 4. In all the above experiments arrange an electro-magnetic time-marker (fig. 161) under the recording lever, so that the points of the recording lever and time-marker write exactly in the same vertical line with each other. In this way one can calculate the time -relations of any part of the curve. The time- marker is arranged to record seconds, and is driven by an electric clock. 5. Effect of Varying Temperatures on the Excised Heart. (a.) Excise the heart of a pithed frog, lay it on a cylindrical brass cooling-box, three inches long and one broad, fixed to a support, and fitted with an inlet and outlet tube, like that in fig. 107. Fix india-rubber tubes to the inlet and outlet tubes of the cooling-box, the inlet tube passing from a funnel fixed in a AMJVJVMJVM J\J\AAAAAAA. Fig. 162.— Parts of a Tracing taken from an Excised Frog's Heart. The temperature was increased gradually from left to right of the curve. stand above the box, and the outlet tube discharging into a vessel below it. Adjust 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, as indicated for other experiments. Take a tracing. (b.) Pass water from io° to 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. 162 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. XL VIII] THE FEOG'S HEART. 227 ADDITIONAL EXERCISES. 6. A more elegant form of heart-lever for studying the movements of the excised frog's heart is shown in fig. 163. Fig. 163.— Marey's Heart-Lever, as made by Verdin. 7. In order to record simultaneously the contractions of auricles and ven- tricle, 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 of both Fig. 164.— Auricular and Ventricular Lever for the Heart of a Turtle or Tortoise. Made by Verdin. must be arranged so that the one writes directly over the other as shown in fig. 164, in the heart of a small turtle or tortoise. 228 PRACTICAL PHYSIOLOGY. [XLIX. LESSON XLIX. STANNIUS'S EXPERIMENT AND INTRA-CARDIAO INHIBITORY MOTOR CENTRE. 1. Stannius's Experiment. — Pith a frog, and expose its heart in the usual way. (a.) With a seeker clear the two aortse from the auricles, and with an aneurism needle pass a moist stout thread between the two aortae and the superior vense cavse; turn up the apex of the heart, divide the fryenum, and raise up 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 thread 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 continues to beat at the same rate as before. After a time, if left to itself, the ventricle begins to beat, but with an altered rhythm. If the relaxed ventricle be pricked, it executes a single contraction. (b.) When the heart is still relaxed, take a second ligature (No. 2), and preferably of a different colour, to distinguish it from No. 1 ; place it round the heart, and tighten it over the auriculo- ventricular 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. (c.) 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. 2. Intra-Cardiac 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. (b.) Prepare previously an induction machine arranged to L.] CARDIAC VAGUS OF THE FROG. 229 give an interrupted current. 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 suffi- ciently strong, the auricles and ventricle cease to beat for a time, but they begin to beat even in spite of continued stimulation. (c.) Stimulate the auricles; there is no inhibition or arrest. (d.) If a drop of solution of sulphate of atropia (Lesson LI. 1) be applied to the heart, stimulation of the crescent no longer arrests the action of the heart, for the atropine paralyses the inhibitory fibres of the vagus. 3. 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 septum, 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. LESSON L. CARDIAC VAGUS AND SYMPATHETIC OP THE PROG AND THEIR STIMULATION. 1. Cardiac Vagus of the Frog — How to Expose it— In this case a preliminary dissection must be made before the student attempts to stimulate the vagus. (a.) 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- legs 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, which reach from the petrous bone to the posterior horn of the hyoid bone (fig. 165). Three nerves are seen coursing round the pharynx parallel to these muscles. The lowest is the hypoglossal (Hg), easily recognised by tracing it forward to the tongue, above it is the vagus in close relation with a blood-vessel (V), and still further forward is the glossopharyngeal (GP). Observe the laryngeal branch of the vagus (L). The vagus, as here exposed outside the cranium, is really the vago-sympathetic. The glossopharyngeal and vagus leave the cranium through the same foramen in the ex-occipital bone, and through the same foramen the sympathetic enters the skull. 230 PRACTICAL PHYSIOLOGY. [L. 2. Stimulation of the Cardiac Vagus. (a.) Adjust a heart-lever so as to record the contractions of the heart on a revolving drum moving at a very slow rate ; or what is perhaps more convenient, tie a fine silk thread round the tip of the apex of the ventricle, and use the recording lever shown in fig. 176. (b.) Place well-insulated electrodes under the trunk of the vagus, stimulate it with an interrupted current, and observe that the whole of the heart is arrested in diastole. The best form of -OH FIG. 165.— Scheme of the Dissection of the Frog Vagus. SM. Submentalis ; LU. Lung; V. Vagus ; GP. Glossopharyngeal ; Hg. Hypoglossal ; L. Laryngeal ; PH, SH, GH, OH. Petro-, Sterno-, Genio-, Omo-hyoid ; HB. Hyoid ; HG. Hypoglossus ; H. Heart ; BE. Branchial plexus. electrodes is the fine shielded electrodes described at p. 157. Although the faradisation is continued, the heart recommences beating. The arrest, or period of inhibition, is manifest in the curve by the lever recording merely a straight line. If the laryngeal muscles contract, and thereby affect the position of the heart, divide the laryngeal branches of the vagus. (c.) Note that when the heart begins to beat again, the beats are small at first and gradually rise to normal. In some instances, however, they are more vigorous and quicker (fig. 166). L] CARDIAC VAGUS OF THE FROG. 23 1 3. Determine the Latent Period. — 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. (b.) Arrange an induction machine for an interrupted current, and keep ]STeef 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, and arrange that when the writing-style on the electro-magnet is depressed — e.g., by means of a weight — the secondary circuit is short-circuited, so that no stimulus is sent along the electrodes under the trunk of the vagus. (c.) When all is ready, lift the weight off 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 YWVWWW Heart Beat. 1 1 1 1 1 1 1 11 1 1 1 1 m 1 1 1 1 1 1 1 1 1 1 1 1 i ' 11 1 1 .11 11 1 1 1 1 : 1 1 1 1 1 1 1 1 1 n ' ' Time in Sees. Stimulation Fig. 166.— Vagus Curve of Frog's Heart. the vasrus. Observe that the heart is not arrested immediatelv. but a certain time elapses — the latent period — usually about one beat of the heart (0.15 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. (e.) Repeat (c.) several times, noting that the heart after arrest goes on beating in spite of continued stimulation. 4. Gaskell'S Method. — Instead of recording the movements of the heart by means of a lever resting on it, a very convenient method is that of Gaskell. (a.) An ordinary writing-lever is placed above the frog-plate on which the frog rests, and supported in the horizontal position by a thin thread of india-rubber, as in figs. 173, 176. Expose the heart of a pithed frog, and leave it in situ. Tie a fine silk thread to the tip of the apex of the ventricle, clamp the aorta to fix the heart in position, and then attach the apex thread to the lever. 232 PRACTICAL PHYSIOLOGY. [L. Every time the heart contracts it pulls down the lever, and the latter is brought into position again when the heart relaxes, by the piece of elastic. 5. 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 angle of the mouth downwards for a short distance. Turn the parts well aside, and expose the vertebral column where it joins the skull. Remove the mucous membrane covering the roof of the mouth. The sym- pathetic is easily found before it joins the vagus emerging from the cranium (fig. 167). Carefully isolate the sympathetic. It lies immediately under the levator anguli scapulae, which must be carefully removed with fine forceps, LAS FlG. 167— Scheme of the Frog's Sympathetic. LAS. Levator anguli scapulae ; Sym. Sympathetic ; GP. Glossopharyngeal ; V.S. Vago-sympathetic ; G. Ganglion of the vagus ; Ao. Aorta ; SA. Subclavian artery (Gaskell). 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. (b.) Expose the heart and attach its apex to a lever supported by an elastic thread as in Gaskell's method (fig. 176). Record several contractions, and then stimulate 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. (c.) If desired, the vagus may be isolated and stimulated, and the effects of the two nerves compared (although the vagus outside the skull is really the vago-sympathetic). Stimulation of the intracranial vagus — i.e. , before it is joined by the sympathetic — is somewhat too difficult for the average student, and is there- fore omitted here. LL] ACTION OF DRUGS ON THE HEART. 233 LESSON LL ACTION OF DRUGS AND THE CONSTANT CUR- RENT ON THE HEART-DESTRUCTION OP THE CENTRAL NERVOUS SYSTEM. 1. Action of Drugs on the Heart — Muscarin, Atropin, and Nicotin. — Either the excised heart, placed in a watch-glass, or the heart in situ may be used. (a.) Pith a frog, expose its heart, and with a fine pipette apply a drop of serum or normal saline containing a trace of muscarin, which rapidlv arrests the rhvthmical action of the heart, the ventricle being relaxed — i.e, in diastole — and distended with blood. (b.) After a few minutes, with another pipette apply a few drops of a o. 2 per cent, solution of sulphate of atropia in normal saline, the heart gradually again begins to beat rhythmically. (c.) Ligature and divide the frsenum, raise the heart by the ligature, and faradise the crescent or inhibitory centre ; the heart is no longer arrested, because the atropin has paralysed the intracardiac inhibitory mechanism. (d.) In another frog, arrest the action of the heart with pilocarpin, and then apply atropin to antagonise it that the heart beats again ^fter the action of atropin. (e.) Apply nicotin (.2 milli- gram). Stimulation of the vagus no longer arrests the heart's action, but stimulation of the sinus venosus does ; so that nicotin paralyses the fibres of the vagus, and leaves the intracardiac inhibitory mechanism intact. observing 2. Effect of a Constant Current on the Heart. (a.) Expose a pithed frog's heart. Cut out the heart, dividing it below the auriculo-ventricular groove, thus obtaining an paration which does not beat spontaneously. Fig. 168. — Support for Frog's Heart. E. Electrodes : 11. Heart. apex " pre- 234 PRACTICAL PHYSIOLOGY. [LI. (b.) By means of sealing-wax, fix a cork to a lead base 5 cm. square, cover the upper end of the cork with sealing-wax, and thrust through it two wires to serve as electrodes, about 4 mm. apart (fig. J 68), 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. (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 con- stant current passes through the living preparation. 3. The Staircase. (a.) To a glass slide used for microscopic purposes (3 x 1) fix with sealing- wax two copper wires in the long axis of the slide, and let their two free ends be about 3 millimetres 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. (6.) Expose the heart of a frog, make an '; apex preparation," and place it on the electrodes on the glass slide. Rest on the heart a heart-lever properly balanced and arranged to record its movements on a slow-moving drum (5 mm. per second). The preparation 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-circuit the secondary circuit, depress the Morse key, short-circuit the secondary circuit, and close the Morse key again. Repeat this several times every ten seconds, and note that the ampli- tude of the second contraction is greater than the first, that of the third than the second, the third than the fourth, and then the successive beats have the same amplitude (fig. 169). Allow the heart apex to rest for a few mimites, 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 •Fl^- 169.— Staircase ag ^e « staircase." The increment is not equal in each Beat. successive beat, but diminishes from the begmuing to the end of the series. (d.) 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. (e.) If 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 Tonus. (a.) Destroy the brain of a frog, and expose its heart in the usual way, 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 pin into the spinal canal, destroy the spinal cord, and leave the pin in the canal to prevent LIL] PERFUSION OF FLUIDS. 235 bleeding. Observe that the heart still continues to beat, but it is pale 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. If 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. LESSON LIL PERFUSION OF 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 the blood is thoroughly shaken up with air before mixing it. This is the best fluid to use. (b.) 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. (c.) Ringer's Fluid. — Take 99 cc. of .6 per cent. NaCl solution, saturate it with calcic phosphate, and add 10 cc. of a 1 per cent, solution of potassic chloride. 2. Preparation of the Heart. (a.) Pith a frog, expose its heart, ligature and divide the frsenum behind the ligature. (b.) Take a two-wayed cannula (fig. 170), attach india-rubber tubing to each tube, and fill the tubes and cannula? with the fluid to be perfused. Pinch the india-rubber tubes with fine bull-dog forceps to prevent the escape of the fluid. (c.) Tie a fine thread to the apex of the ventricle. To this thread a writing-lever is to be attached. (d.) By means of the frsenum ligature raise the heart, with a pair of fine scissors make a cut into the sinus, and through the opening introduce the double cannula passed through a cork, until its end is well within the ventricle. Tie it in with a ligature, the ligature constricting the auricles above the auriculo-ventricular Flo. 170.— Kronecker's Cannula for Frogs Heart. 236 PRACTICAL PHYSIOLOGY. [LIL 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, fill it with the per- fusion 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 the 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 the level is horizontal, and writes freely on a slow-moving recording drum. Every JIG. lyi.-Tracing obtained from a Frog's Heart, time the heart Contracts it through which Dilute Blood was perfused. The raises the lever, and dur- eontracting heart raised a registering lever. . ,. , , 7, „,, The lower line indicates seconds. mg diastole the lever tails (fig. 171). In this way it is possible to use various fluids for perfusion. The fluids may be placed in separate reservoirs, each communi- cating with the inlet tube, and capable of being shut off or opened by clamps as required. Further, by poisoning the supply fluid with atropin, muscarin, spartein, or other drug, one can readily ascertain the effect of these drugs on the heart, or the antagonism of one drug to another. Instead of a glass funnel as a reservoir for the fluid, one may use a Marriotte's flask (fig. 172), the advantage being that the pressure 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-Recorder (of Schafer). The heart is tied to a two-way cannula as before, and is introduced 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 ihe piston. The piston records on a slow-moving drum placed horizontally. Lin] ENDOCARDIAL PRESSURE. 237 LESSON LIII. ENDOCARDIAL PRESSURE-APEX PREPARATION- 1. Endocardial Pressure in the Heart of a Frog. (a.) Proceed as in the previous experiment (a.), (6.) (omit c), (d.). {b.) Arrange a frog's mercury manometer provided with a writing-style as in fig. 172. Attach the inlet tube of the cannula to the Marriotte's flasks (a, b), and connect the outflow with the tube of the mercury manometer. It is well to have a T-tube between the heart and the manometer, but in the heart apparatus, as shown and used, the exit tube is preferable. See that no air-bubbles are present in the system. Every time the heart con- tracts the mercury is displaced and the writing-style is raised, and records its movements on a slow - moving drum. (c.) Take a tracing with the outflow tube and Marriotte's flask shut off, so that the whole effect of the contrac- tion 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 either 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. €— 0^^ Fig. 172.— Scheme of Kronecker's Frog Manometer. 2. Apex Preparation. — In this pre- paration of the heart only the apex of the heart is used. As a rule, it does not beat spontaneously until sufficient pressure is applied to its inner surface by the fluid circulating through the heart. (a.) Proceed as in Lesson LII. 2, («), (b.) (omit c), (d.), with this differ- ence, that in (d.) the cannula is placed deeper into the ventricle, and the ligature is tied round the ventricle below the auriculo-ventricular groove. Excise the heart and cannula, and attach it to the heart apparatus as in the previous experiment. (b. ) If the " heart apex " preparation does not contract spontaneously, stimu- late 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. 238 PRACTICAL PHYSIOLOGY. [LIV. (c.) By introducing an electro-magnet with a recording lever into the primary circuit (Lesson XXXIV.), and having a time-marker recording at the same time, one can determine the latent period of the apex preparation. It is about 0. 1 5 sec. id.) If desired, the effect of a constant current may be studied in this way instead of by the method described in Lesson LI. 2. The apex beats rhythmically under the influence of the constant current. LESSON LIV. GASKELL'S CLAMP-HEART-LEVER— TONOMETER. 1. Gaskell's Clamp. (a.) On a suitable support arrange two ordinary 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 12 cm. apart. About mid- way between the two place a Gaskell's clamp (fig. 173, 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 r the points of a fine pair of forceps, which can be ap- proximated by means of a screw. (b.) Expose the heart of a pithed frog. Tie a fine silk thread to the apex of the ventricle, and another FIG. i 73— Gaskell's Clamp. C. Heart in clamp ; to the upper part of the A. Auricular, and V Ventricular lever ; E. auricleS, and excise the heart. Elastic to raise J. after it is pulled down. ' . 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. 173, C) so as to clamp the heart in the auriculo-ventricular 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, LI V] GASKELLS CLAMP. 239 fix the two levers so that both are horizontal, and adjust the caoutchouc thread attached to the upper one, so that it just sup- ports 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. Fig. 174. -Tracing from Auricle (A) and Ventricle (F) by Gaskell's Method. T. Time in seconds. (d.) Adjust a time-marker to write exactly under the writing- points of the two levers. Moisten the heart from time to time with serum or dilute blood. (e.) After obtaining a tracing where the auricle and ventricle contract alternately (fig. 174), screw up the clamp slightly until the ratio of auricular to ventricular contraction alters — i.e., until, by compressing the auriculo-ventricular groove, the impulse from the auricles to the ventricle is " blocked " to a greater or less FIG. 175.— Tracing of a Frog's Heart taken with Apparatus shown in Fig. 176. II. Heart-tracing ; T. Time in seconds. extent, when the auricles will contract more frequently than the ventricle. 2. Heart-Lever and Gaskell's Clamp. — Gaskell's clamp may also be used with the heart in situ, the apex of the ventricle being fixed by means of a cord to a writing-lever as is shown in fig. 176. Take a tracing of an exposed frog's heart by means of the 240 PEACTICAL PHYSIOLOGY. [LIV. heart-lever shown in fig. 176. The apex of the ventricle is tied to the lever; first the auricles contract and pull it down slightly, then the greater contraction of the ventricle pulls the lever down Fig. 176.— Shewing the Arrangement of the Frog and Lever for a Heart-Lever, supported by a fine elastic thread. further, and when the ventricle relaxes, the lever is raised by the elastic. Fig. 175 shows the kind of tracing obtained when the heart is free and no clamp is applied. ADDITIONAL EXERCISE. 3. Roy's Frog-Heart Apparatus or Tonometer. — This apparatus registers the change of volume of the contracting heart. Fig. 1 77 shows a scheme of the apparatus, and fig. 178 the apparatus itself. 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 upright. In the brass 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 on to it. In this cylinder works a light aluminium piston (p), slightly less in diameter than the cylinder. Around the lower aperture of the cylinder is tied a piece of flexible animal membrane, the ligature resting in the grooved collar. The free 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-lever {I) fixed below the stage. The bell-jar is filled with oil (0), while in its upper opening is fitted a short glass stopper, perforated to allow the LIV.] GASKELLS CLAMP. 241 passage of a two-wayed 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 perfumers for covering the corks of bottles — in the form of a tube round the lower end of the grooved cylin- der ; afterwards the lower end of the membrane is fixed to the piston, taking care that the needle attached to the piston hangs towards the record- ing lever. Drop in a little glycerin to moisten the membrane. {b.) Fill the jar with olive-oil, and have the recording apparatus ready adjusted. Prepare the heart of a large frog [Lesson LIL, (a.), (b.) (omit c), {d.)], the cannula used being one fixed in the glass stopper of the bell-jar, and al tach the inlet tube of the cannula to the reserve ir of nutrient fluid, while the outlet tube is arranged so as to allow fluid which has passed through the heart to drop into a suitable vessel. (c.) Introduce '[ the cannula, with - the heart at- tached, into the oil, and see that the stopper is securely fixed. Open the stopcock (e), and allow some oil to flow out of 0, thus rendering the pressure within sub-atmospheric ; and as Fig. 177. — Scheme of Roy's Tonometer. FIG. 173.— Roy's Tonometer, as made by the Cambridge Scientific Instrument Company. Q 242 PEACTICAL PHYSIOLOGY. [LV. 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 LV. HEART- VALVES-STETHOSCOPE-CARDIOGRAPH - POLYGrRAPH-MEIOCARDIA- REFLEX INHIBI- TION OF THE HEART. 1. The Action of the Valves in the Dead Mammalian Heart. — This is of value in order that the student may obtain a know- ledge of the mechanical action of the valves. The heart and lungs of a sheep — with the pericardium still unopened — must be procured from the butcher. (a.) Open the pericardium, observe its reflexion round the blood-vessels at the base of the heart. Cut off 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 tubing, 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. (6.) 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, which lies behind it — tie the long tube, the flange securing it completely. Ligature the in- ferior 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 PA. tube, as it is supported by the closed semilunar valves. If the right ventricle be compressed rhythmi- cally, 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 held 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 LV.] HEART-VALVES. 243 bulgings corresponding to the position of the sinuses of Val- salva. (c.) Repeat (ft.), if desired, on the left side, tying the long tube into the aorta, and the short tube into a pulmonary vein, ligatur- ing the others. (d.) 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 tricuspid valves ; notice how the three segments come into apposition, while the upper surfaces of the valves themselves are nearly horizontal. (<\) With a pair of forceps tear out one of the segments of the semilunar valves of the pulmonary artery. Tie a short tube into the P. A., and to it attach an india-rubber 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 you please, there is no escape of fluid through 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 with the excised aorta in a filter stand, and pour water into the funnel; much of it will escape through the coronary arteries ; ligature these. The semi- lunar valves are quite competent, i.e., they allow no fluid to escape between their segments. Hold a lighted 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. (g.) Slit open the pulmonary artery, and observe the form and arrangement of the semilunar valves. (li.) Make a transverse section through both ventricles, and compare the shape of the two cavities and the relative thickness of their respective walls. (1.) Study two casts of the heart (after Ludwig and Hesse), (1) in diastole, and (2) in systole. (J.) 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. 2. 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 244 PRACTICAL PHYSIOLOGY. [LV. impulse, apply the small end of the stethoscope over this spot, and listen with the ear applied to the opposite end of the instru- ment. The left hand may be placed over the carotid or radial artery to feel the pulse in either of those arteries ; compare its time-relations with what is heard over the cardiac impulse. (b.) 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 prsecordia, noting that the first sound is heard loudest at the apex beat, while the second is heard loudest at the second right costal carti- lage at its junction with the sternum. 3. The Cardiograph. — Several forms of this instrument are in use, including those of Marey (fig. 179), Burdon-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 sixth ribs on the left side, and about half an inch inside the mammary line. (b.) Arrange the cardiograph by connecting it (fig. 179) with stout india-rubber tubing to a recording Marey 's tambour adjusted to write on a drum (fig. 132). It is well to have a valve or a T-tube capable of being opened and closed between the receiving and record- ing tambours, in order to allow air to escape if the pressure be too great. (c.) Adjust the ivory knob of the cardiograph (jp) over the car- diac impulse where it is felt most, and take a tracing. Fix, varnish, and study the tracing. 4. Polygraph of Knoll and FIG. 170. — Marey s Cardiograph, p. Button — , ., mi • • j_ i placed over cardiac impulse ; s. Screw Rothe. — IhlS IS a most convenient to regulate the projection of p ; t. apparatus, both for work in the Tube to other tambour. r r ' .. laboratory and at the bedside. Moreover, it is so arranged that two tracings can be t.aken simultaneously. It is made by H. Rothe, Wenzelbad, Prague. It can be used to take simultaneously cardiac impulse and a pulse tracing, or respiratory movements and a pulse tracing, or two pulse tracings. LV.] HEART-VALVES. ^45 Fig. 180 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 motion. M is a time-marker beating seconds. H, H, are two Marey's registering tambours adjus- table on the stand C. B is a tambour which can be fixed 246 PKACTICAL PHYSIOLOGY. [LV. over an artery or over the cardiac impulse, while A is a bottle- shaped caoutchouc bag which can be strapped to the body for studying the respiratory movements. (a.) Adjust the tambour (B) over the cardiac impulse, and fix 3 Fig. 181.— H. Tracing of the cardiac impulse, the respiratory movements of the chest not being arrested. the bag (A) on the abdomen so as to record simultaneously the cardiac impulse and the respirations (fig. 181). The experi- menter may also take a tracing of the cardiac impulse while the respiration is arrested. FIG. 182.— Showing the Method of Fixing the Receiving Tambour of Eothe's Polygraph on an Artery. (b.) Take a tracing of the radial pulse and the respiratory movements. Fig. 182 shows how the receiving tambour is ad- justed over an artery. At the same time record the respirations, and note in the tracing (fig. 183) how the number and form of LV.] HE ART- VALVES. the pulse-beats vary during inspiration number being greater during inspiration. 247 and expiration — the Fig. 183. — P. Tracing of radial pulse ; It. Respirations ; T. Time in seconds. (c.) Take a tracing of the radial pulse and the cardiac impulse simultaneously (fig. 184). FIG. 184. — P. Tracing of the radial pulse ; H. Of the cardiac impulse ; T. Time in seconds. 5. Reflex Inhibition of the Heart. (a.) Place one hand over the chest of a rabbit and feel the beating of the heart. With the other hand suddenly close the nostrils of the rabbit, or bring a little ammonia near the nostrils, so as to cause the animal to close them. Almost at once the 248 PRACTICAL PHYSIOLOGY. [LVI. heart can be felt to cease beating for a time, but it goes on again. 6. Effect of Swallowing on the Heart-Beats. (a.) With your 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 your pulse. Count the in- crease 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. ADDITIONAL EXERCISE. 7. Meiocardia and Auxocardia. (a.) Bend a glass tube about 20 mux in diameter into a semicircle, with a diameter of about 6 to 8 inches. Taper off 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 off the edges of the glass in a gas-flame. (&.) 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 auxo- cardia, i.e., when the heart is largest; while it is drawn farther into the tube 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 of the heart during its several phases of fulness, altering the volume of air in the lungs. LESSON LVI. THE PULSE-SPHYGMOGRAPHS-SPHYGMO- SCOPE-PLETHYSMOGRAPH. 1. The Pulse. (a.) Feel the pulse of a fellow- student, count the number of beats per minute ; compare its characters with your own pulse, including its volume and compressibility. Observe how its characters and frequency are altered by (1) muscular exercise; (2) a prolonged and sustained deep inspiration; (3) prolonged expiration ; and (4) other conditions. 2. The Sphygmograph. — Many forms of this instrument are in use. Study the forms of Marey and Dudgeon. Marey's Sphygmograph (fig. 185). Mode of Application. — (a.) Cause the patient to seat himself beside a low table, and place his forearm on the double-inclined plane (fig. 185), which, in the improved form of the instrument, LVL] THE PULSE. 249 is the lid of the box so 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 300 with the dorsal surface of the hand. (b.) Mark the position of the radial artery with ink or an aniline pencil. See that the clock (H) is wound up, and apply the ivory pad of the instrument exactly over the radial artery C Fig. 185.— Marey's Sphygmograph applied to the Arm. where it lies on the radius, and fix it to the arm by the non-elastic straps (K, K). The sphygmograph must be parallel to the radius, and the clockwork must be next the elbow. Cover the slide with enamelled paper, smoke it, fix it in position, and arrange the writing-style (C) so as to write upon the smoked surface (G) with the least possible friction. Regulate the pressure upon the Fig. 186. -Tracing taken from the Radial Artery by means of Marey's Sphygmograph. A. A hard, and B, a softer pulse. artery by [means of the milled head (L), i.e. amplitude of the lever is obtained. (c.) Set the clockwork going, and take i scratch on the name, date, and pressure. (d.) Study the tracing obtained (fig. 1S6). until the greatest tracing. Fix it, Fig. 187. — Dudgeon s Sphygmograph. Fig. 188.— Tracing of Radial Pulse taken with Dudgeon's Sphygmograph. Fig. 189.— Ludwig's Sphygmograph, made by Petzold of Leipzig. LVL] THE PULSE. 251 3. Dudgeon's Sphygmograph (fig. 187). (a.) Adjust the instrument on the radial artery by means of an elastic strap, carefully regulating the pressure — which can be graduated from 1 to 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. 188). 4. Ludwig's Improved Sphygmograph. — Use this instrument (fig. 189). 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. ADDITIONAL EXEKCISES. 5. Action of Amyl Nitrite. (a.) With the sphygmograph adjusted, take a tracing, and then place two drops — not more — of amyl nitrite on a handkerchief, and inhale the vapour. 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. The Gas Sphygmoscope (fig. 190). (a.) Connect the inlet tube of the instrument with the gas supply, light the gas-flame (&). Apply the caoutchouc membrane (a) over the radial artery, Fig. 190.— Gas Sphygmoscope, made by Rothe of Prague. and observe how the flame rises and falls with each pulse-beat. Take a deep expiration, and observe the dicrotism in the gas-flame. 7. Plethysmography — 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 a volatile oil — e.g., clove. 252 PRACTICAL PHYSIOLOGY. [LVIL LESSON LVII. RIGID AND ELASTIC TUBES-THB PULSE-WAVE -SCHEME OP THE CIRCULATION — RHEO- METER. 1. Rigid and Elastic Tubes. — To the vertical stem of a glass T-tube or three-way tube i cm. in diameter, fix an elastic pump whose opposite end dips into a vessel of water. To the other 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. Arrange to 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 off the elastic tube near the T-piece. Work 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 out- flow tube, and keep pumping ; the water still flows out in an intermittent 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. (b.) Elastic Tube. — Clamp off the glass tube near the T-piece, and unclamp the flexible one so as to have no resistance at its outflow end. "Work the pump ; the outflow takes place in jets corresponding 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 intro- duce 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 continuous 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 converts the interrupted into a uniform flow* LVIL] RIGID AND ELASTIC TUBES. 253 This apparatus serves also to demonstrate why there is no pulse in the capillaries, and under what circumstances a pulse is pro- pagated into the capillaries and veins. 2. Velocity of the Pulse-Wave. (a.) Take about 3 metres of india-rubber tubing about 6 mm. in diameter. To one end of the tube attach an ordinary 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 part of the tube near the pump under the lower lever, and resting on a suitable support, while part of the tube near the outflow end is similarly arranged under the upper lever. Regulate the pressure of the lever upon the tube by means of lead weights. (6.) Arrange on the same stand a Deprez's chronograph to record the vibra- tions of an electro-tuning-fork, vibrating 30 or 50 D.V. per second. See that the writing-points of the two levers and the chronograph write upon the drum in the same vertical line. (c.) Set the tuning-fork vibrating, allow the drum to move, compress the elastic pump interruptedly — 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 the water, the tube distends and raises 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 con- traction of the heart, 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 heart 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 abcissa, and the other where the upper 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 Eutherford's scheme or the major schema. In the latter, the heart is represented by an ordinary elastic pump, 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. (a.) Use two mercury manometers, and 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 in the same vertical line on a revolving cylinder, the venous one a little below the arterial one. (6.) Un clamp all the arteries, and work the pump, regulating the number of beats by means of a metronome beating 30 times 254 PRACTICAL PHYSIOLOGY. [LVII. per minute, and compress the heart to the same extent each time with a lemon-squeezer. Observe that both manometers oscillate nearly to the same extent with each beat. Take a tracing on a slow-moving drum. (c.) Gradually clamp the arteries to offer resistance, and continue to work the pump ; the pressure in the arterial mano- meter 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. (d.) While the mean arterial pressure is high, cease pumping ; this will represent the arrest of the heart's action, brought about Fig. 191.— 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. by stimulation of the peripheral end of the vagus ; the arterial blood-pressure falls steadily. (e.) Begin pumping again until the mean arterial pressure is restored, and then un clamp 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. (g.) The velocity of the pulse-wave may be estimated as in Lesson LVII. LVIL] RIGID AND ELASTIC TUBES. 255 ADDITIONAL EXERCISES. 4. Rigid and Elastic Tubes. — Arrange an experiment as shown in fig. 191. 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 flows into the tubes, they are compressed rhythmically to imitate the interrupted beat of the heart. Observe that more fluid is discharged by the elastic than by the rigid tube. 5. The Rheometer (fig. 192) is used to measure the amount of blood flowing through a vessel in a given time. 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. (a.) To represent the heart — or the weight of a column of fluid — arrange a Marriotte's flask or funnel on a stand, and to the outflow-tube attach a narrow india-rubber tube, and clamp it after filling it with defibrinated blood. Suppose the tube to represent an exposed artery, clamp or apply and tighten two ligatures, about an inch apart, round the middle of the tube. Fill one bulb of the instrument with defibrinated blood and the other with clear almond-oil, and close the top of the instrument with a glass plug. {b.) Divide the part of the tube included be- tween the two ligatures, and tie into either end the nozzles provided with the instrument. Call the one next the reservoir or heart k, and the other one k. Fix the instrument into the nozzles, the bulb A being filled with oil and in connec- tion with h, B with defibrinated blood and con- nected with 1c. The instrument is fixed in posi- tion by a support provided with it, while a handle which fits into two tube-sockets on the upper surface of the disc (e, ei) 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 off 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 upper end of the artery. As soon as the bulb A is filled with blood, which is indicated by a mark on the glass, the disc is suddenly rotated, whereby B communicates with h, and A with k. The blood now flows into B, displacing the oil in it into A, and as soon as this takes place, the disc is again rotated. This process is repeated several Fig. 192.— Rheometer. 256 PRACTICAL PHYSIOLOGY. [LVIII. times. Count the number. The bulbs have the same capacity and are exactly calibrated, so that to measure the amount of blood flowing through the blood-vessel we require to know the time occupied. 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, or a tuning-fork may be used. Example. — Suppose each bulb holds 5 cc, and suppose the bulbs to be filled ten times with blood during 100 seconds, i.e., 50 com. flowed from the tube in I second. Suppose 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.e., the quantity of fluid flowing across any section in unit of time -f area of that section. Hence — V = Q 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. 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 calcu- late the velocity of the flow in the tube. LESSON LVIII. CAPILLARY BLOOD-PRESSURE-LYMPH-HEARTS -BLOOD-PRESSURE AND KYMOGRAPH. 1. Blood-Pressure in the Capillaries. (a.) Make the following apparatus (fig. 193), consisting of a slip '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 plate. Place the glass plate (a) over the skin on the dorsal surface of the 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. (b.) Test how altering the position of the hand affects the pressure in the capillaries. 2. Examine with a microscope the circulation in the web of a frog's foot, or in the mesentery of a frog with its brain destroyed, and afterwards slightly curarised. (a.) Apply a drop of croton oil or mustard for a minute or less, and observe the inflammation thereby produced, and the changes in the appearance of the blood-vessels and the blood-flow, until LVIIL] CAPILLARY BLOOD-PRESSURE. 257 the latter is finally arrested in a condition of stasis, and exudation takes place. 3. The 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, which are situated one on each side of the urostyle (fig. 194). (b. ) Remove 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 not synchronous with the blood-heart, whose move- ments can usually be distinguished without opening the chest. Fig. 193.— Apparatus used by V. Kries for Estimating the Capillary Blood- Pressure. Fig. 194.— Posterior Pair of Lymph-Hearts (L) of the Frog. (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 animal?, 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. A. (a.) 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 glycerine is added to make it flow freely. R 258 PKACT1CAL PHYSIOLOGY. [LVIII. (&,) Partially fill the manometer with dry clean mercury, and in the open limb of the manometer place the float, provided with a pen or sable brush moistened with aniline ink containing a little glycerine. See that the float rests on the convex ^surface of the mercury (fig. 1 95). (c.) The closed or proximal side of the manometer at its upper 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 *r\ india-rubber tubing connecting the cannula with the lead tube is placed a clamp. The proximal end of the manometer is filled by means of a syringe with a saturated solution of sodic carbonate as high as the stem of the T-piece. To it is attached a long india-rubber tube, which is connected with a pressure - bottle filled with a saturated solution of sodic carbonate, and kept in posi- tion by a cord passing over a pulley fixed in the roof. A clamp com- presses the india-rubber tube just above the manometer. Open this clamp and also the one at the end of the lead pipe. The alkaline solu- tion fills the whole system, and after it does so, and no air-bubbles are present, 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 smoothly on the paper, and that it is kept in contact with the latter by a silk thread with a shot attached to its lower end. B. To Insert the Cannula. — (a.) Arrange the necessary instru- ments in order on a tray — scissors, scalpels, forceps (coarse and fine), seeker, well waxed ligatures, small aneurism needle, bull-dog forceps, cannulae, sponges. (6.) 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 scalpel. 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, depressor, 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 FIG. 195.— Simple Form of Kymograph. On the right is the manometer, the float re- cording the movements of the mercury on a simple revolving cylinder. LVIIL] ARTERIAL BLOOD-PRESSURE. 259 carotid, under it, and internal to the vagus, are seen two fine nerve? : the more internal and finer one is the depressor or superior cardiac branch of the vagus (fig. 196), the other is the sympathetic. Note that the smallest ** of the three nerves is the depressor, which is easily isolated from the sym- pathetic by means of a 6eeker. If in doubt, trace the sympathetic up- wards until it merges into the large swelling of the superior cervical sym- pathetic ganglion. The depressor should be tied low down in the neck and divided below the ligature, as if for an experiment on its function. It is an afferent nerve, and therefore its central end must be stimulated. The vagus should also be isolated and ligatured as if for experiment. It is well to use shielded electrodes, such as are shown in fig. 197. The vagus is tied and divided, and if its peripheral end is to be stimulated, the peripheral end is drawn through the shielded electrodes, which are then connected with the secondary coil of an induction machine. To complete the arrangements, an in- duction machine ought to be set up. (c.) 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 fine aneurism needle, withdraw the needle, and ligature the artery. About an inch on the cardiac side of the latter, clamp the artery with bull-dog for- ceps. Raising the artery slightly by the ligature, with a fine-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 artery, 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. Pill the cannula with the soda solution, and into the cannula slip the glass nozzle at the end of the lead pipe, tying it in securely. 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 re- move 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. (d.) Before joining the lead tube to the cannula, isolate the vagus, the Fig. >6.— Nerves in the Neck of the Rabbit. a. Sympathetic ; b. Hypoglossal, with c, its descending branch (descendens noni) ; d. Branch of a cervical nerve joining c ; e. Vagus, with /, its superior laryngeal branch ; a and h, the origins of the supe- rior cardiac or depressor nerve. VjULStS^ Fig. 197. — Forms of Shielded Ekctrodes for Stimulating the Vagus or a Deeply - Seated Nerve. 260 PRACTICAL PHYSIOLOGY. [LVIII. largest of the three nerves ; put a ligature 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 from the sympathetic, as it is the smallest of the three nerves accompanying the carotid. In the dead rabbit the depressor may be traced up to its origin by two branches, one from the vagus, and the other from the superior laryngeal (fig. 196). 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. {e.) In every case a base-line or line of 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. Fig. ic -Blood-Pressure Tracing of the Carotid of a Dog, taken with Ludwig's Mercurial 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 right angles to this has engraved on it a millimetre scale. Or use a millimetre scale as in fig. 198. Read off the height in millimetres from the base-line to the lowest point in the curve, and also to its highest point ; take the mean of the two, and multiply by two, this will give the mean arterial pressure. Instead of measuring only two ordinates, measure LVIIL] ARTERIAL BLOOD-PRESSURE. 26 1 several, and take the mean of the number of measurements. In all cases the result has to be multiplied by two. (g.) Measure the blood-pressure tracing (fig. 199) of the carotid of a dog from the base-line T. It represents the effect of stimulation of the vagus, and the arrest of the heart-beat, and the consequent great fall of the blood-pressure. (h.) In every kymograph tracing, notice the smaller undu- lations due, each one, to a single beat of the heart, and the larger ones due to the respiratory movements (fig. 199). In a blood- pressure tracing taken from a dog with the vagi not divided, observe that the size of the heart-beats on the descent of the FIG. 199. — B.P. Blood-pressure tracing of dogs carotid, stimulation of the vagus at the indent in the line S ; T, indicates time in seconds, and is the abscissa. respiratory wave is 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. 199). (ii.) The central end of the depressor, (iii.) The central end of a sensory nerve. 5. To Make a Glass Cannula. — Heat in the flame of a blowpipe a piece of hard glass tubing about 5 mm. in diameter. When it is soft, take it out of the flame, draw it out gently for about 3 cm. Allow it to cool ; make the gas jet smaller, heat the thin drawn-out part of the tube, and draw it out very slightly. This makes a shoulder. With 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 orifice is thus obtained. Round off the oblique edges either by a file, rubbing them on a whetstone, or heating 262 PRACTICAL PHYSIOLOGY. [LIX. 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 shoxilder, the form shown in fig. 200 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, how- ever, be shown on a rabbit or cat just killed. If the vagus be rapidly exposed, and the chest opened to observe the still beating heart, on stimu- lating the peripheral end of the vagus with an interrupted current, the movements of the heart are seen to be arrested for a short time — the heart itself being in diastole. 7. Effect of Swallowing on the Heart (p. 248). Fig. 200. — Improved Form of Arterial Cannula, by Francois-Frank. A is tied into the artery ; B is attached to the lead tube of the manometer; and C, the lateral tube, is closed with an elastic (clamped) tube. PHYSIOLOGY OF RESPIRATION. LESSON LIX. MOVEMENTS OP THE CHEST WALL-ELASTI- CITY OP LUNGS-HYDROSTATIC TEST. 1. Movements of the Chest Walls — Stethograph. A. Rabbit. — (a.) Arrange a drum and time-marker. Fix a rabbit conveniently, and with tapes tie on its chest Marey's double tambour (fig. 201), connecting the latter with a recording tambour adjusted to write on the drum. Introduce between the receiving and recording tambours either the valve usually supplied with Marey's apparatus or a T-tube with 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 LIX.] MOVEMENTS OF THE CHEST WALL. 263 cardiac impulse, the tracing will show also the number of beats of the heart (fig. 202). B. Man — (b.) Stethograph (Mareijs). — Cause a person to expose his chest. Raise the screw (g) of the stethograph, and Fig. 201. — Marey's Double Tambour, to be tied round the chest of a rabbit. fix the plate (/) of the instrument on the chest, with tapes attached to (c) and (d). Depress (g), connect the tube (a) with a recording tambour, with the same precautions as in 1, A., and FlG. 202.— Stethograph Tracing of a Rabbit. The tracing shows undulations due to the beats of the heart. T indicates time in seconds. take a tracing (fig. 203). Examine the tracing, noting the rela- tion between inspiration and expiration. (c.) Polygraph {Rothe). — Use the polygraph of Rot lie. record the respiratory movements by means of the bag (fig. 180, A), and study the tracing (fig. 204). 264 PRACTICAL PHYSIOLOGY. [LIX. 2. Elasticity of the Lungs. (a.) Remove the whole of the front of the chest in the rabbit already used. Observe the collapsed lungs. To the tracheal cannula attach an india-rubber bag such as is used with a spray- producer, and inflate the lungs, Cease to pump air into the lungs, and observe how they collapse. Fig. 203. — Marey's Stethograph. 3. Hydrostatic Test. (a.) Cut out the lungs and the heart. Place them in a vessel of water. The whole will float, as the lungs contain so much air. Cut off a small piece of one lung, throw it into water; Fig. 204.— Stethograph Tracing, taken with Eothe's polygraph. 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. Note that several LIX] MOVEMENTS OF THE CHEST WALL. 265 seconds elapse before the next inspiration. This is the period of apnoea. 5. Deglutition Apnoea. (a.) Test how long you can "hold your breath." Note the time. (6.) 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. 248. Other centres are influenced by sipping. 6. Voluntary Respiration. — Test on yourself how long this can be kept up. As a rule, one cannot continue it for more than two minutes. ADDITIONAL EXERCISES. 7. Stethometer of Eurdon-Sanderson. (a.) Prepare a drum and time-marker as in the previous experiments. Cause a person to expose his chest, and seat himself conveniently. The instrument is suspended by a broad band placed round the neck, the horizon- tal bar being behind the body. (6.) The most important diameters of the chest to measure are — "Those connecting the eighth rib in the axillary line with the same rib on the oppo- site side, the manubrium sterni with the third dorsal spine, the lower end of the sternum with the eighth dorsal spine, and the ensiform cartilage with the tenth dorsal spine." Measure only the first. Adjust the knob of the tam- bour 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 T-piece, 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.) Pix 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 half full with coloured water, and to the proximal limb attach an india-rubber tube with a T-piece and screw clamp, as in other experiments. Connect the tracheal cannula with the manometer tube, tighten the screw clamp, and see that the water stands at the same level in both limbs of the manometer. (6.) Open both pleurae without injuring the lungs. The lungs collapse and the water is depressed in the proximal side of the manometer, and rises in the open limb. 266 PRACTICAL PHYSIOLOGY [LX. LESSON LX. VITAL CAPACITY-EXPIRED AIR-PLEURAL PRESSURE-BLOOD GASES. 1. Vital Capacity. — Estimate this on Hutchinson's spiro- meter, 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 instrument, &c. 2. Changes in Expired Air. (a.) Black's 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 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. (b.) Muller's Valves. — Arrange two flasks (A and B) and tubes as in fig. 205, with some lime-water in both. Close the nostrils, apply the mouth to the tube, and inspire. The air " cn /: 1 J~ — v / ,L ] ts r, ." passes in through A, and is freed of any CO2 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- jar without a bottom. Ascertain that a lighted taper burns in the jar. Renew the air, place in the neck of the latter a glass tube with a piece of india-rubber tubing attached. Close the nostrils, apply thelmouth to the tube, and inspire. The water rises in the bell-jar. 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 passages. Remove the cork, and place a lighted taper in the expired air. The taper is extinguished (fig. 206). Fig. 205.— Muller's Valves. LX.] VITAL CAPACITY, ETC. 267 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). 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 point of the trocar lies in the space between the two layers of the pleura Fig. 206.— Hey wood's Experiment. Fig. 207. — Gases collected over mercury. A ball of caustic potash absorb- ing the C09. Observe how the level of the water rises in the proximal limb of the mano- meter, indicating the negative pressure in the pleural cavity. 5. Gases in the Blood. — Blood yields about sixty volumes per cent, of gases to a vacuum. The gases in the blood — CO^, 0, and N— are extracted from it by means of a gas-pump. Various forms have been constructed, including those of Ludwig, Pfliiger, and Alvergniat. Study these various forms and the principle of their construction. It requires a considerable amount of time to become thoroughly acquainted with the practical working of these instru- ments, but this is not necessary from a student's point of view. (a.) Suppose the gases of the blood to be extracted ; they are collected in a eudiometer over mercury (fig. 207). Or, for practice, and merely to grasp the principle how the relative proportion of the gases in a mixture is ascertained, the student may use air containing a small quantity of carbon dioxide. (6.) Fuse a ball of potash on the end of platinum wire (best done in a bullet-mould). Introduce this under the mercury into the gases in the eudio- meter. The caustic potash absorbs all the C02 (twenty-four hours), and the diminution in volume represents the proportion of CO? in the mixture. 268 PRACTICAL PHYSIOLOGY. [LXI. (c.) 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, which rapidly absorbs the oxygen. The decrease in volume represents the amount of 0. The remainder of the gas present represents N. 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.) LESSON LXI. LARYNGOSCOPE-VOWELS. 1. The Laryngoscope is used to investigate the condition of the 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, per- forated with 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 pro- vided for the purpose. B. On a Living Person. — (a.) Place the patient upright in a chair. A good source of artificial light — e.g., a suitable Argand lamp — is placed near the side of the patient's head, a little above the level of his mouth. The new incandescent lamp gives a brilliant, clear, and steady light. Mr. Mackenzie's rack-move- ment lamp is a most convenient form. The observer seats him- self 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 illumi- nated. The patient is then directed to incline his head slightly backwards, to open his mouth wide, and protrude his tongue. Place a clean handkerchief over the tongue, and give the patient the handkerchief 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 LXL] LAKYNGOSCOPE. 269 operator moving his head slightly to and from the patient until the greatest brightness is obtained. (c.) Take the small laryngeal mirror in the right hand, and warm it gently over the lamp to prevent the condensation of moisture on its surface. Test its temperature on the skin of the cheek or the back of the hand. Holding the handle of the mirror as one does a pen, rapidly carry it horizontally backwards, avoiding contact with any structures in the mouth, until its back rests against the base of the uvula. At the same time, direct the beam of light upon the laryngeal mirror, when an inverted ima^e of the larynx will be seen more or less perfectly. (d.) By moving the laryngeal mirror, not, however, pressing too much on the uvula, or continuing the observation for too long a time, one may explore the whole of the larynx. Perhaps com. FIG. 20S. — View of the Larynx during a Deep Inspiration, g.e. Glosso-epi- glottidean fold ; I.e. Lip and cushion of epiglottis; a.e. Ary - epiglottic fold; c.W.. c.S. Cartilages of Wris- berg and Santorini ; v.c. Vocal cord ; v.b. Ventricular band ; p. v. Processus vocalis ; c.r. Cricoid cartilage ; t. Rings of trachea. Fig. 209.— Larynx during Vocalisation. f.i. Fossa innominata ; h.f. Hyoid fossa ; com. Arytenoid commissure. only the posterior part of the dorsum of the tongue 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 glosso-epiglottidean folds, come into view. In the middle line are the true vocal cords, which are pearly white and shining, and best seen when a high note is uttered, and between them the chink of the glottis. Above these are the false vocal cords, which are red or pink, the ary-epiglottidean folds, with on each side the cartilages of Wrisberg farthest out, the cartilages of Santorini internal to this, and the arytenoid cartilages near the middle line, (e.) Make the patient sing a deep or high note, or inspire feebly or deeply, and observe 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 laryn- 270 PRACTICAL PHYSIOLOGY. [LXI. geal mirror on his right or left corresponds to the patient'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. %. Auto-Laryngoscopy. — The student should learn to use the laryngoscope on himself. The student sits in a chair, fixes the large reflecting mirror in a suitable holder about eighteen inches in front of, and on a level with his mouth. Behind and to one side of this an ordinary plane mirror is placed vertically. On one side of his head he places the source of light. The light 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 Fig. 210.— Konig's Manometric Flame Apparatus. 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 front of a toilet mirror. In a line with and slightly behind the mirror, and on one side of the observer, 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. (a.) Use Konig's apparatus, as shown in fig. 210. Connect the tube of the capsule with the gas supply, light the gas-jet, and sing the vowels A, E, I, O, U in front of the open trumpet-shaped tube shown in the figure. With the other hand rotate the mirror (M), and observe the serrated reflec- tion of the flame in the mirror, noticing how the image in the mirror varies with each vowel sounded. LXIL] REFLEX ACTION, ETC. 27 1 PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM. LESSON LXII. REFLEX ACTION-ACTION OF POISONS- KNEE-JERK. 1. Reflex Action. — Destroy the brain of a frog, which should be done without loss of blood. Place under a bell- jar a normal frog for comparison. Observe that immediately the frog is pithed, on pinching one of its toes, very probably the leg will not be drawn up. Allow the frog to rest for half an hour or more (by this time it has recovered from the shock of the opera- tion), and 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. (p.) 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. Observe that it makes no spontaneous movements, if left entirely to itself. (d.) 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. Extend 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 both 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 272 PRACTICAL PHYSIOLOGY. [LXII. hook hang up the frog on a suitable support. It hangs vertically with the legs pendant. At first the legs may make a few move- ments, but they soon cease to do so, and hang quite motionless. (a.) Pinch the tip of any toe of the right leg; the right leg is flexed and drawn up. If a toe of the left leg be pinched, either with the nail or forceps, the left leg is drawn up. These are unilateral reflex movements. (b.) Pinch the tip of one toe very feebly, 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, there- fore, that the reflex movement varies not only with the part of the skin stimulated (1, d), but also with the intensity of the stimulus. Yery 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). (a.) Prepare dilutions of sulphuric acid containing 1, 2, 3, and 4 cc. per litre — i.e., 0.1, 0.2, 0.3, and 0.4 per cent, of sulphuric acid — and place some of each in four shallow glasses. Arrange also a large beaker of water to wash the frog. Adjust a metro- nome to beat one hundred times per minute. Cause it to beat. (6.) 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 1 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 acid. 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 observa- tions— 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 the strength of the acid increases, the latent period becomes shorter, but not in the ratio in which the acid is stronger. 4. Chemical Stimulation. (a.) In a small glass place some strong acetic acid and a few pieces of filter-paper 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 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., LXII] REFLEX ACTION, ETC. -/ J purposive, -well-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 move- ments by chemical than by mechanical stimuli. (b.) After an interval of five minutes repeat the experiment, but hold the leg to which the acid is applied. In all probability the other leg will be moved, and the opposite foot will be used to 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 different reflex movements will be elicited, if sufficient interval for recovery (five minutes at least) be allowed between the suc- cessive experiments. (d.) With a needle destroy the spinal cord ; all reflex action is then abolished, although the nerves and muscles retain their excitability and the heart continues to beat. Expose the heart and observe it beating. Test the excitability of the nerves and muscles in the usual way with an interrupted current. 5. Action of Strychnia. (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 sulphate of strychnia (0.5 per cent.). (&.) 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 violent tetanic spasms — or general tetanus — of the whole body. During the paroxysm of convulsions, the limbs are stretched out, extended, hard, and rigid, while the trunk is similarly affected. The extensor muscles are more affected than the flexors. The tetanic paroxysm passes off, to be soon followed by another on the slightest stimulation. (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. 6. Action of Potassic Chloride or Bromide or Chloral. (a.) Prepare a reflex frog as in Lesson LXII. 1. Test the latent period with dilute sulphuric acid, 0.2 per cent., until con- stant results are obtained. Inject 2 minims of a 1 per cent, solution of KC1 or KBr or C2HC130, and after ten minutes time again test the latent period. Within a short time the latent period will be greatly prolonged. 7. Knee-Jerk. (a.) 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 S 274 PRACTICAL PHYSIOLOGY. [LXIII. right ligamentum 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 other nervous affections ; so that its pre- sence or absence is a most important clinical symptom. (b.) The knee-jerk is readily obtained in a rabbit. 8. 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 paraplegia. Soon after the circulation is restored in the cord and lower limbs, the para- plegia disappears. LESSON LXIII. NERVB-ROOTS-RBACTION TIME. 1. Functions of the Roots of the Spinal Nerves. — To expose the roots, destroy the brain of a frog, 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 vertebrae. 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 vertebras. With a blunt-pointed pair 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 — and with an aneurism needle carefully place a fine silk thread (say a red one) under it. (a.) 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 peripheral or distal end of the nerve- root, place it on well-protected electrodes, and stimulate it with an interrupted 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 of the seventh and tenth nerves. Observe that the whole limb 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 experiments on the anterior root of the ninth nerve, i.e., place a ligature round it, tighten the ligature, and divide the nerve between the cord and the ligature. Stimulate the distal end with an inter- rupted current ; this causes contraction of the muscles of the limb supplied by this root. LXIII] NERVE-ROOTS, ETC. 2/5 Stimulate the central (e.) Repeat the experiment on the eighth nerve-root, end ; no effect is produced. From the effects of section and stimulation of the nerve-roots, one concludes that the anterior are motor, and the posterior are sensory. ADDITIONAL EXERCISES. 2. Reaction Time, i.e., the interval between the application of a stimulus to a sense-organ and the moment the stimulus is responded to by the indi- vidual. The Neuramoebometer (Exncr), or Psychodometer {Obcrstcin), con- sists of two uprights (S), with a horizontal axis carrying a spring (F) — which vibrates ioo I).V. per second — with a writing-style at its free end (fig. 211). A brass plate (B — b) 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 catch (G) until the latter meets the spring (F), and puts (F) on the stretch. Pig. 211. — The Neuramoebometer. When the catch (G) is withdrawn, (F) vibrates, and if the style be arranged to touch the glass, a curve is obtained on the latter. (a.) It requires two persons. The observed person places a finger on the knob (K), while the catch (G) and glass plate are pushed 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. (6.) The observer suddenly pulls on (H), thus discharging 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. (d.) In the more complete form of the 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 placed 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. 3. Another Method. — Apparatus. — Two Grove's cells, Morse and Du Bois key, Deprez' signal, chronograph in circuit with a tuning-fork of 250 D.V. per 2^6 PRACTICAL PHYSIOLOGY. [LXIV. second, electro-magnet with a writing- style, drum moving about 30 cm. per second, induction-machine, electrodes, wires. (a.) Arrange in circuit the two Grove's cells, a Du Bois key, induction-coil for single shocks, Deprez' signal with writing-style and a Morse key. Let the Du Bois key be near the observer, and the Morse key near the observed person. Arrange the signal to record on the drum, and directly under it allow a chronograph (250 D.V.) to record its vibrations. (6.) Suppose the electrodes from the induction-machine are applied to the tongue of the person to be experimented on, start with the Du Bois key open, and the Morse key closed. The observer suddenly closes the Du Bois key, the observed person being so placed that he cannot see when this is done. This moment is recorded by the signal as it is in circuit. The observed person feels the induction-shock, and at the same moment he presses the Morse key, and thus breaks the circuit, whereby the armature of the signal is set free. The interval between the two events, calculated from the vibrations of the tuning-fork, gives the reaction time. The experiment must be repeated several times, and the mean of several observations taken. 4. Inhibition. (a.) 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 move- ments 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. 5. Kircher's Experimentum Mirabile. (a.) Take a hen and hold it gently to restrain its movements. Bring its bill in contact with a table, and then 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 may be rolled to one side or the other, yet it lies quiescent. (6.) Repeat the same process, but instead of a white line lay a straw or white thread over the base of its bill. In a short time the animal becomes quiescent. Notice the alteration of the heart-beat and the depth and number of the respirations. PHYSIOLOGY OF THE SENSE ORGANS. LESSON LXIV. FORMATION OP IMAGE - DIFFUSION - ABERRA- TION — ACCOMMODATION - SCHEINER'S EX PERIMENT — NEAR AND FAR POINTS— PURKINJE'S IMAGES -PHAKOSCOPE — ASTIG- MATISM-PUPIL. 1. Formation of an Inverted Image on the Retina. (a.) Fix the fresh excised ox-eye provided for you, remove the sclerotic from part of the posterior segment of the eye near the LXIV.] DIFFUSION. 277 optic nerve. Roll up a piece of blackened paper in the form of a tube, black surface innermost, and place the eye in it with the cornea directed forwards. Look at an object — e.g., a candle- flame — and observe the inverted image shining through the retina and choroid. (b.) Focus a candle-flame or other object on the ground-glass plate of an ordinary camera for photographic purposes, and observe the small inverted image. (c.) Fix the fresh excised eye of an albino rabbit in Du Bois-Reymond's apparatus provided for you, and observe the same phenomenon. The eye is fixed in with moist modeller's clay. Observe the effect on the retinal imajje 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.) 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 onlv at a certain distance from the lens. If the white screen be nearer or farther away, the image is blurred. (b.) 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. (c.) Prick a smooth hole in a card with a needle, arrange the needle at the proper distance to obtain the previous diffusion effect, and now introduce the card between the needle and the eye, bringing the card near the eye, and looking through the hole in the card. The needle will appear distinct and larger ; it is distinct because the diffusion circles are cut off, and larger because the object is nearer the eye. 3. Spherical Aberration. (a.) 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.) Fix steadily the limit between a white and black surface, and while doing so bring an opaque card between one eye and the object (the other eye being closed), with its edge parallel to the limit between the white and black surfaces, so as to cover the 2jZ PEACTICAL PHYSIOLOGY. [LXIV. larger part of the pupil. The margin next the black appears with a yellow fringe when the part of the pupil which lies next the black surface is covered, while there is a blue fringe in the opposite condition. (b.) Look at a candle- or gas-flame through a small hole in a black card with cobalt glass placed behind the hole, which allows only the red and violet rays to pass through it. Accommodate for the violet rays or approach the light, the flame appears violet, surrounded with a reddish halo ; on accommodating for the red, or on receding, the centre is reddish with a violet halo. (c.) V. Bezold's Experiment. — Make a series (10 to 12) of concentric circles, black and white alternately, each 1 mm. thick, the diameter of the whole being about 15 mm. On looking at these circles when they are placed within the focal distance, one sees the white become pink ; 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 from a distance outside the far point of vision ; the white appears red and the black bluish. {d.) Wheatstone's Fluttering Hearts. — 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 of the eyes, and give it a gentle to and fro motion. On continuing to look at the hearts, they will appear to move or flutter over the blue background. 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 near finger ; a distinct image is obtained of it, while the far one is blurred or indistinct. Look at the far image ; it becomes distinct, while the near one becomes blurred. Observe that in accommodating for the near object one is conscious of a distinct effort. (b.) 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 somewhat from behind ; the half of the pupil 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. (c.) 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 versa. (d.) At a distance of six inches from the eyes hold a veil or LXIV.] ACCOMMODATION. 279 thin gauze in front of some printed 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. Schemer s Experiment. (a.) 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. (b.) Close one eye, and with the other look through the holes at the near needle, which will be seen distinctly, while the far needle will be double, but both images are somewhat dim (fig. 212). (c.) With another card, while accommodating for the near needle, close the right - hand hole ; the right-hand image disap- pears ; and if the left- hand hole be closed, the left-hand image disap- pears. (d.) Accommodate for the far needle ; the near needle appears double. Now close the right-hand hole, and the left-hand image disappears; and on closing the left - hand hole, the right - hand image disappears (fig. 212). (e.) Instead of using a card perforated with two holes, use the apparatus provided for you, so constructed that one hole is covered with a green and the other with a red glass. Repeat the previous P. ' r" R, Fig. 212.— Scheiner' s Experiment P, 28o PKACTICAL PHYSIOLOGY. [LXIV. II U Fig. 213 observations, noting the disappearance of the 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. (g.) Make three holes in a piece of cardboard, as in fig. 213, a, so that they can be brought simultaneously before one eye, and look at a pin or needle. One sees three images of the £ qC needle. On looking at a near OO 0 1 O object, the needles are in the position b, and at a distant object in that shown in c. \k.) Miles' Experiment, (i.) Make a pin-hole in a card. Look through the hole at a pin. Accommodate for the pin, move the card to and fro, and note that the pin appears 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. 7. Determination of Near and Far Points. (a.) Place one of the vertical needles used in the previous experiment conveniently, and with one eye — the other eye being closed — look through the two holes in a card, and when one dis- tinct 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 backwards while looking at the needle, observing when it becomes double. This indicates the far point of accommodation. N.B. — The experiment (&.) succeeds best in short-sighted individuals. (c.) Determine the near point with a vertical needle and card with horizontal holes, and again with a horizontal needle and a card with the holes vertical. The two measurements do not usually coincide, because the curvature of the cornea is usually different in the two meridians. 8. Purkinje-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 accommodate for a distant object, 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 LXIV.] ACCOMMODATION. 28l is a second less brilliant and not sharply defined erect image, which, of all the three images, appears to lie most posteriorly. It is reflected from the anterior surface of the lens. The third image lies towards the opposite margin of the pupil, is the smallest of the three, and is a sharp inverted image reflected from the pos- terior surface of the lens. 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 undergoes a change in its curvature during accommodation. (6.) Instead of using a candle- flame, cut two small square holes (10 mm. square) 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 position on a table a large convex lens, supported 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. Move a lighted candle at the side of this arrangement, and observe the three 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 demonstrate more clearly the change in the curva- ture of the crystalline lens dur- ing accommodation (fig. 214). (a.) Place the phakoscope in a con- venient position, and darken the room. Two persons are required. The ob- served eye looks through a hole in the box opposite to c, while the observer looks through the hole (a) at the side. Light a lamp, place it some distance from the two prisms (b, b') 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 eve two larger less distinct images, from the anterior surface of the lens, and two smaller and much dimmer images, from the posterior surface of the lens. The last are seen with difficulty. (b.) Ask the observer to accommo- date for a near object, viz., the pin above c, keeping the eye unmoved. Ob- serve that the middle image becomes smaller and goes nearer to the corneal one, while the other two undergo no per- ceptible change. At the same time the pupil becomes smaller. Fig. 214.— Phakoscope. a. Hole for observer's eye ; b, b'. Prisms ; c. Carries a pin for the observed eye to fix as its near point 282 PRACTICAL PHYSIOLOGY. [LXIV. 10. Line of Accommodation, i.e., the eye does not accommo- date for a point, but for a series of points, all of which are equally sharply perceived with a certain accommodation. (a.) Stretch a white thread about a metre long on a blackened wooden board. Through two narrow slits in a blackened card, about 2 mm. apart, 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 focussed is quite distinct and linear, but beyond or nearer than this the thread is double, and diverges from the point focussed. (b.) 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, we can see at one and the same time only one of the objects ; but not the point, and the print equally sharply defined. Remove the eye gradually from the glass plate, and ultimately 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. 11. Astigmatism is usually due to unequal curvatures of the cornea in different meridians. (a.) Draw on the card supplied to you two black lines of equal thickness, intersecting each other at right angles. Fix it verti- cally at the far limit of accommodation and look at it, when pro- bably 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. (b.) Instead of a cross, construct a star, the lines radiating at equal angles from the centre, and being of equal thickness. Re- peat the previous observations, observing in which meridian the lines are most distinct. (c.) Repeat these observations with the " astigmatic clock " suspended on the wall, or with appropriate illustrations given in Snellen'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 distance. All the parts will not be equally distinct. Approach the card towards you, noting in which diameter the 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 behind the hole in the card and look into the observed eye, noting the reflection of the circles to be seen in the eye. Observe in which meridian the circles are most distinct, and if there be any per- ceptible 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 apart. LXV.] BLIND SPOT. 283 Fix the card vertically at a distance, and move towards it, noting whether the vertical or horizontal lines are most distinct. (g.) Fix a fine wire or needle vertically in a piece of wood moving in a slot, and similarly fix another needle or wire hori- zontally. 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. 12. Diplopia Monophthalmica. (a.) Make a small hole in a black card, hold it at some distance, and with one eye look 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 paper, and the long rays remain in the same position. Compare the figure obtained from the other eye. It will very likely be different. 13. 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, 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. ('?.) Place in front 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 arrests the lateral rays that fall upon the eyeball. 14. The Pupil Appears Larger than it is in Reality. (a.) To see the pupil of its exact size, an excised eyeball must be observed in water. If a glass model of a pupil be taken, and then be covered by an- other thick concavo-convex glass in shape like the cornea, the pupil at once appears larger. LESSON LXV. BLIND SPOT -FOVEA CENTRALIS - DIRECT VISION-CLERK-MAXWELL'S EXPERIMENT - PHOSPHENES-RETINAL SHADOWS. 1. The Blind Spot. (a.) Marriotte's Experiment. — On a white card make in the same horizontal line a black cross and a circle about three inches + FIG. 215.— Marriotte's Experiment. apart, as in fig. 215. The cross and the circle may be black on white or coloured card. Hold the card vertically about ten inches 284 PRACTICAL PHYSIOLOGY. [LXV. from the right eye, the left being 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 the entrance of the optic nerve. On bringing the card nearer, the circle reappears, the cross of course being visible all the time. + Fig. 216. (h.) 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. 216, keep both eyes open, and on moving the paper to and fro at a certain distance both black dots will disappear. {f. ) Close one eye, and fix the point a (fig. 217) ; on moving the Fig. 217. paper a certain distance (about 16 cm.), one sees a complete cross, and to most observers the horizontal bar appears uppermost. 2. Map out the Blind Spot. (a.) Make a cross on the centre of a sheet of white paper, and place it on a table about ten or twelve inches from you. Close the left eye, and look steadily at the cross with the right eye. 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 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 down- ward direction, in each case marking where the pencil becomes invisible. If LXV.] DIRECT VISION. 2S5 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. ( 4. Acuity of Vision of the Fovea Centralis. {a.) On a horizontal plane — a blackboard — describe a semicircle with a radius equal to that of the near point of vision, and fix in the semicircle pins at an angular distance of 50 apart. Close one eye, and with the other look at the central pin ; the pins on each side will be seen distinctly ; those at io3 begin to be indistinct, while those at 300 to 400 are not seen at all. (6.) At a distance of five feet look ab a series of vertical parallel lines alter- nately black and white, each .5 mm. wide. A normal eye will distinguish them ; if not, approach the object until they are seen distinctly. 5. Direct Vision. — When the image of an object falls on the fovea centralis, we have what is called "direct vision/' but when the image falls on any other part of the retina, it is called " indirect vision. " Vision is most acute at the fovea centralis of the yellow spot. (a.) Standing about two feet from a wall, hold up 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. Hence, in looking at a large surface, to see it dis- tinctly 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 outwards, inwards, upwards, and downwards successively, and note that as the dots are moved towards the periphery they appear as one, but not at equal dis- tances from the fixed point in all meridians. For convenience, the card may be moved along a rod, movable on a vertical support. 6. Clerk-Maxwells Experiment — The Yellow Spot. (a.) Make a strong watery solution of chrome alum, filter it, and place it in a clear glass bottle with flat 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 oval or round rose spot will be seen in the 286 PRACTICAL PHYSIOLOGY. [LXV. Fig. 218. — Bergmann's Experiment. otherwise green field of vision. The pigment in the yellow spot absorbs the blue-green rays, hence the remaining rays which pass 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 two to three yards. In a short time the lines will appear as in fig. 218, A. They appear of this shape be- cause of the manner in which the images of the lines fall on the cones in the yellow spot, as shown in B. 8. Phosphenes. (a.) Press the finger firmly, or better still, the head of a round-headed pin, against the inner corner of the closed eye. A brilliant circular patch, with a steel-grey centre and yellow cir- cumference, is seen in the field of vision and on the opposite side, and of 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., beyond into space. The phosphene is seen in the upper half if the lower is pressed, and vice versd. 9. Shadows of the Fovea Centralis and Eetinal Blood-Vessels. (a.) Move, with a circular motion, a blackened card with a pin-hole in its centre in front of one eye, looking through the pin-hole at a white cloud. Soon a punctated field appears with the outlines 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. (a.) In a dark room light a candle, and stand in front of a monochromatic 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 LXV.] RETINAL SHADOWS. 287 vision, 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, will be seen on a dark background. Therefore the parts of the retina stimulated by light must lie behind the retinal blood-vessels. 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 with one eye, and on the illuminated part of the lens will be seen images of dots and threads due to objects within the eyeball. 12. Inversion of Shadows thrown on the Retina. (a.) Make three pin-holes in a card, and arrange them in a triangle close to each other. Hold the card four or five 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. Ketinal 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. (a.) 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 re- tina lasts a certain time. 14. Talbot's Law. — A grey once produced is not changed by increased rapidity of rotation of the disc exciting the sensation. The intensity of the light impres- sion is quite independent of the absolute duration of the periods of illumination and shade. FlG- 2I9- (a.) Rotate a disc like fig. 219 twenty-five times per second, then the period in which illumination and shade alternately lasts for the inner zone is 771- sec, for the middle r\r, and for the outer zone jfo sec. In all three zones 288 PRACTICAL PHYSIOLOGY. [LXVI. 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 number of rotations is readily determined by Hard- ing's improved counter. LESSON LXVI. 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 two 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 ex- tent the fingers can be separated horizontally, vertically, and in oblique directions before they disappear from his field of vision. (b. ) Priestley Smith's Peri- meter (fig. 220). — Let the observer 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 which way the chart is to be placed, (c.) The patient rests his right cheek against the knob on the 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 1 Fig. 220. — Priestley Smith's Perimeter. LXVL] PERIMETRY, IRRADIATION, ETC. 289 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 repeated for four or more meridians, and the n 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 fur that eye. (/.) Test the field of vision for colours, substituting for the white travelling disc blue, red, and green. Mark each colour-field on the chart with a pencil of similar colour. Xotice that the field for blue is nearly as large as the normal visual field. It is smallest for green, red being intermediate between green and blue. {g.) 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 their free ends, and the two fields of vision will be seen to meet and form a single field. (b.) Continue the convergence, and note that two fields re- appear, but they are crossed. 3. Circular Rotation of the Eyeballs (Secondary and Tertiary Positions). («.) On a grey sheet of stout paper, at least one metre square, rule a number of vertical and horizontal black lines. Fix on one part of the paper a strip of red paper ; gaze steadily at the latter, keeping the head fixed. After a time suddenly direct the eyeballs to another part of the grey surface ; an after- image is seen which retains its same relative position with regard to the vertical and horizontal lines, provided the eyeballs be moved directly upwards, downwards, inwards, or outwards. In these " secondary positions " there is no rotation of the eyeball on its antero-posterior axis. (b.) 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. 4. Irradiation. — By irradiation is meant the fact that, under certain circumstances, objects ap- pear larger than they fig. 22i.-irradiation. 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 221, or two squares of exactly T 290 PRACTICAL PHYSIOLOGY. [LXVI. the same size, of white and of black paper. Place the white patch on a black, and the black on a white sheet of paper. Hold them some distance from the eye, and especially if they be not dis- tinctly focussed, the white circle will appear larger than the black one. (b.) Divide a square into four, as shown in fig. 222, 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 they appear to run into each other and to be joined together by a white bridge. (c.) Look at fig. 223, placed at such a distance that the ac- commodation is imperfect. The white stripe, which is of equal breadth throughout, appears wedge-shaped, being wider below Fl<3. 222. Fig. 223. 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 paper 5 mm. wide, and parallel to each other, leaving a white interspace of 8 mm. between them. Look at the object, 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 line, 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. (p.) Make on a white card two squares of equal size, omitting the outlines. Across the one draw horizontal lines at equal dis- 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 — i.e., both appear oblong. LXVL] PERIMETRY, IRRADIATION, ETC. 2QI (c.) Look at the row of letters (S) and figures (8). To some the upper halves of the letters and figures may appear to be the bbbbbbbb 88888888 Fig. 224. 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 considerable difference between the two, the lower half being considerably larger. (d.) 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. 225 ; the long oblique lines do not appear to be parallel, although they are so. 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 at a convenient distance. In both cases one will not succeed at first. In these cases one loses the impressions produced by the convergence of the optic axes, which are impor- tant factors in judging of distance. (6.) 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. Fig. 225. — Zollner's Lines. 292 PRACTICAL PHYSIOLOGY. [LXVI. (a.) Hold a straight edge just below the level of the eyes. Its upper margin shows a slight concavity. (6.) In indirect vision the appreciation of direction is still more imperfect. While leaning on a large table fix a point 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-point, 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. (a.) Fix the centre of fig. 226 at a distance of 3 to 4 cm. from the eye, when by indirect vision the broad white and black areas Fig. 226. of the peripheral parts, bounded by hyperbolic 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 LXVIL] PERIMETRY, IRRADIATION, ETC. 293 fixed object, and then gradually converge the tubes ; the object appears larger and nearer. (6.) Look at an object through two pieces of glass {2\ x l\ x \ in.), held at first in the same plane, one in front of each eye. Let the adjoining edges of the 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 eyeballs must converge to a greater or less extent, as the case may be, with the result that the object ap- pears larger or smaller, or appears to approach or re- cede as the plates are rotated. Special forms of apparatus contrived by Rollett, and another by Landois, are used for this purpose. 10. Apparent Move- ments. (a.) Strobic Discs. — Give the discs a somewhat cir- cular but rapid movement, and observe that the rings appear to move, each one on its own axis. (b.) Radial Movement. — Wh ile another person rotates a disc like fig. 227 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 becoming larger, disappear at the periphery. After long fixation 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 recede. If the disc be rotated in the opposite direction, the opposite results are obtained. (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 (Beaunis). Fig. 227. LESSON LXYII. KUHNE'S ARTIFICIAL EYE-MIXING COLOUR SENSATIONS-COLOUR-BLINDNESS. 1. Kuhne's Artificial Eye. (Fig. 22S.) (or.) Fill the instrument with water, and place it in a darkened room with the cornea directed to a hole in a shutter, through which sunlight is directed by means of a heliostat. If this is not available, use an oxy-hvdrogen lamp or electric light to throw parallel rays of light on the cornea. If these cannot 294 PEACTICAL PHYSIOLOGY. [LXVII. be had, use a fan-tailed gas-burner, but in this case the illumination and images will be very feeble. To enable one to observe the course of the rays of light, pour some eosin or fluorescin into the water in the instrument. (&.) Formation of the 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. (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. Fig. 228. — Ktihne's Artificial Eye, as made by Jung of Heidelberg. {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, with a hole cut in it to act as a diaphragm to cut off some of the marginal rays, be interposed, the image is somewhat improved. (e.) After seeing that the light is sharply focussed on the retina, remove the lens — to imitate cataract — and observe that the rays are focussed quite behind the retina. (f, ) 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 has to be used after removal of the lens for cataract. (g.) Astigmatism. — Fill the plano-convex glass (g) — to imitate a cylindrical lens — with water, and place it in front of the cornea. Between the cornea LXVIL] MIXING COLOUR SENSATIONS. 295 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 less 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. Move the retina towards the cornea, and observe two images ; close the right-hand hole and the right-hand image disappears. Bring the retina posterior to the principal focus, and again there are two images. On closing the right-hand hole the left-hand image disappears, and vice versa. 2. Mixing of Colour Sensations. (a.) Lambert's Method. — On a black background place a blue wafer or square of blue paper, and six or seven inches behind it Fig. 229.— Rothe's Rotatory Apparatus for Colour Discs. It is so arranged as to give various rates of rotation by combining the motions of 1, 2, and 3. a yellow square or wafer. Hold a plate of clear glass vertically, about ten inches above and midway between the two squares. Look obliquely through the glass, and get the reflected image of yellow to overlap the blue, seen directly through the glass ; where they overlap appears white. (b). Arrange on the spindle of the rotating apparatus the disc with coloured sectors provided for you (fig. 229). On rotating the disc rapidly, observe that it appears grey or whitish. The disc is provided with sectors corresponding to the colours of the spectrum, and arranged in varying proportions. (c.) Arrange three of Clerk-Maxwell's colour discs — red, green, and violet — upon the spindle of the rotating apparatus. Adjust the relative amounts of these three colours, so that on rapidly rotating them they give rise to the 296 PRACTICAL PHYSIOLOGY. [LXVII. 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 different colour to be slipped over the other, and thus many discs can be superposed, and the amount of each colour exposed regulated in any desired proportion. (d.) 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 spindle arrange a white and a black disc — with a diameter a little more than half that of the former pair — the white being in the proportion of 21.3 to 78.7 of the black. On rotating, a grey colour is obtained from both sets of discs. 3. To Test Colour-Blindness. — On no account is the person being tested to be asked to name a colour. In a large class of students one is pretty sure to find one or more who are more or less colour-blind. The common defects are for red and green. (a.) Place Holmgren's worsteds on a white background in a good light. Select, as a test colour, a skein of a 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.g., pink, yellow. A coloured plate showing these should be hung up in the labora- tory. Any one who selects all the greens and do confusion- colours has normal colour vision. If, however, one or more con- fusion-colours be selected, proceed as follows : — Select, as a test colour, a skein of pale rose. If the person be red-blind, he will choose blue and violet ; if green-blind, grey and green. (b.) Select a bright red skein. The red-blind will select green and brown ; the green-blind picks out reds or lighter brown. 4. Successive Light Induction. (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. (6.) Look at two small white square patches of paper 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 strip. 5. Contrast. (a.) On the rotating machine cause a disc, as in fig. 230, to rotate with moderate rapidity, when several zones will be seen, the innermost black, while each one farther outwards is lighter LXVIL] COLOUB-BLINDNESS. 297 in tint. Each zone, where it abuts against the inner darker zone. is lighter than the rest of the same zone, and shades off gradu- ally to the outer part of the zone. (b.) Place a small white square or oblong piece of paper on a dull, dead, black surface. Stare steadily at the white square, and observe that the edges ap- pear whiter than the centre. (c.) 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. (d.) Place side by side a white and black surface. Cut two oblong (t \" x ^") pieces of grey, yellow, or other coloured paper of exactly the same size, and lay one piece of the grey on the fIG. 230._Disc for Contrast, 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. (e.) Place on a table a small sheet (4" x 4") of red and one of green paper. Cut out of a sheet of red paper two pieces about one inch square, and place them on the two large squares. Ob- serve that the small red square on the green ground appears far 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. (g.) On an ordinary mirror place a slip of transparent coloured glass — red or green, or any other colour. Hold in front of the coloured glass a narrow strip of white paper ; by adjusting 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. The black print is seen green in the posterior image. Gum a few narrow strips of white paper (I mm. in diameter) on black paper, and on holding it up in front of the red glass, as before, the anterior image appears in the complementary of the glass, viz., gteen. 298 PRACTICAL PHYSIOLOGY. [LXVII. (h.) 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 — e.g., cardboard, with a clean-cut vertical edge. A part of the white surface is illuminated by all four candles, then 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 appears 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 parts, and the parts most affected 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. 6. Simultaneous Contrast. (a.) 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 with a thin semi-transparent sheet of tissue paper. The grey oblong appears pink. (b.) Instead of green paper place the grey slip on red, and cover it as before ; a greenish-blue contrast colour is seen. (c.) Repeat (a), but place a red square on a grey ground; the red square will appear greenish. (d.) A grey square upon blue appears yellow; a yellow upon blue appears white, when covered with tissue paper. (e.) Surround the small square with a broad black line, each square appears in its own colour. The effect of contrast is destroyed. (/.) Place side by side two strips of paper, green and red (6x3 in.). Over the line of junction place a strip of grey paper (|x6 in.), and cover the whole with tissue paper, as be- fore. 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 strip. Do the same with yellow and blue. (g.) Arrange a disc like fig. 231 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 stripe. On rotating the disc, the ring which one might expect to be grey, from the black and white, appears reddish — i.e., the complementary colour of the greenish ground. (h.) 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 Fig. 231. — Disc for Simultaneous Contrast. LXVIL] COLOUR-BLINDNESS. 299 white much darker. Fix the eyes for a minute on a point midway between the strips ; close and cover the eyes. The after-images will show a great difference in luminosity. (i.) Ragona Scinas 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 450 between them (fig. 232). 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 6 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 greenish- blue square alongside a red one. 7. Coloured Shadows. (a.) Place an opaque vertical rod (i inch in diam.) in front of a white background. Admit not too bright day- light to cast a shadow of the rod. Place a lighted candle behind one side of the rod, the shadow caused by the Scirm's"" Expert yellow-red light of a candle, and illuminated by the ment. 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 effect is more pronounced the darker both shadows are. To show that the blue is purely 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 18 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. (6.) In a window-shutter of a dark room cut two square holes (10 cm.) on the same horizontal plane, and two 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. Both openings must be provided with a movable shutter to regulate the amount of light admitted. At three to four 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. 8. Choroidal Illumination. (a.) In a dark room light an ordinary lamp or fan-tailed gas-burner. Place the source of light at the right side, about two 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. (b.) With the conditions as in (a), hold a piece of paper (3-4 cm. wide), or a 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 (a.). Hold the cardboard about ten 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 300 PRACTICAL PHYSIOLOGY. [LXVII. 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 (H. Seivall). The colour-phenomena occur without the aid of objective colour, and are due to light passing through the sclerotic and choroid coats. 9. Binocular Contrast. (a.) Place a white strip of paper on a black surface, look at the white paper and squint so as to get a double image. In front of the right eye place 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. 10. Positive After-images. (a.) In a room not too brightly illuminated, rest the retina by closing the eyes for a minute or two, then suddenly look for a second or two at a gas-jet surrounded with a white globe, then close the eyes. An image corresponding exactly to that looked at will be seen. (b.) After resting the retina by closing the eyes, 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 within the eye. 11. Negative After-images. (a.) Rest the retina, and then stare steadily for half a minute or less at a small white square or white cross on a dead black ground. To ensure fixation of the eyeballs, make a small mark in the centre of the white paper, and fix this steadily. In all subse- quent experiments do the same. Then suddenly slip a sheet of white paper over the whole, a black square or cross will appear on the white background. I find that the best black surface to use is the dull dead 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. (p.) The black negative after-image may also be seen by closing the eyes. (c.) Look at a dull, dead, black square or cross on a white ground. Turn to a grey surface, when a white square or cross will appear. (d.) Stare intensely at a bright red square on a black surface for twenty seconds, and then look at a white surface, a bluish- LXVIL] COLOUR-BLINDNESS. 30I 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 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. 12. The Haploscope consists of two tubes about an inch and a quarter in diameter and eight inches in length, which can be con- verged or diverged from a fixed point as desired. On looking through the tubes with both eyes, each eye has its own special field of vision, but with the proper convergence the two fields are united, and form one field of vision. (a.) With the discs provided for you — copies of those of Volk- mann — study the combinations obtained in the single field of vision. (b.) Struggle of the Fields of Vision. — Place in one tube a red and in the other a green glass. One sees either a red or green disc, but not a mixture of the two colours. 13. Stereoscope. (a.) Examine a series of stereoscopic slides to show the com- bination of the images obtained by the right and left eyes respectively. (6.) Struggle of the Fields of Vision. — Place in a stereoscope a slide of glass with vertical lines ruled on one half of it and hori- zontal lines on the other half. Look at the two dissimilar images : note that they 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 slide, preferably a geometrical pattern — e.g., a crystal where the boundary-lines are white and the surfaces black. Such a slide shows glance or lustre. &j 14. Lustre in Coloured Objects. This may be shown by looking at a green 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. 302 PRACTICAL PHYSIOLOGY. [LXVIII. LESSON LXVIII. THE OPHTHALMOSCOPE. The Ophthalmoscope. — Two methods are employed, and the student must familiarise himself with both. 1. Direct — giving an upright image. 2. Indirect —giving an inverted image. The observer must practise both methods on another person, or use a rabbit for the purpose, or use an artificial eye. A. Human Eye. — 1. The Direct Method. (° Xantbin. CO C— NH C5H4N402. \ NH-CH Guanin. C5H5N4.0. NH-C=N / 1 >° C=NH C-NH NH-CH Heteroxantbin. C6H6N402. Adenin. C5H4N4.OH. N(CH3)-C=N CO Tbeobromin. CO C-N(CH,) C7H8N402. \ NH - CH Tbeopbyllin. CO C7H8N402. \ Paraxantbin. C,-HsN402. N(CH3)-C=N C-NH II N(CH3)-CH CO N(CH3)-C=N Caffein. CO C,H10N4O2.,;X ;CO C-N(CH3) N(CH3)-CH Hypoxantbin. C5H4N4.0. Carnin. C7H3N40. (Eohmann). RELATION OF UREA TO THE C02 DERIVATIVES AND THE CY-COMPOUNDS. NH, o=c{g| o=c{nh2 o=c{NH2 Carbonic Acid. Carbaminic Acid. Urea=Carbamid. /NH, C02+2NH3=CO^ \0-NH4 Carbamate of Ammonia. APPENDIX. o1: On heating to 130-1400 C. : — /NH2 /NH2 /O-NH4 /NH3 C(T -H20 = CO; CO^ -2H20=CO^ \0-NH4 NHa \O-NH4 NH, Carbamate of Ammonia. Urea. Ammonium Carbonate. Urea. By heating with strong mineral acids or alkalies : — /NH2 /O-NH4 ccr + g2° = co; \nh3 o-xh4 Urea. Carbonate of Ammonia. (Krukcnberg). CORRECTION FOR TEMPERATURE AND PRESSURE IN THE HYPOBROM1TE METHOD (p. 114). 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. Suppose 25 cc. of N passes over into the gas-collecting tube, and that the temperature of the room (t) — io0 C. and the barometric pressure 755 mm. Hg., What is the volume at standard temperature and pressure ? Let V be the required volume at o° 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 = — 2730 ; t = the temperature of the room (in degrees Centigrade + 273) ; then VP* = vjjT : v = — and V = ?7— 1 pT Ft y_25^755x273 760 x 283 J yD Next to urea, uric acid is the most important substance present in urine which is decomposed by the 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 : — V= ylx^ 76o(i+a<) V= the required volume at standard temperature, o° C, and 760 mm. II _:. V1= the volume at the observed temperature and pressure. h= the observed pressure. a= the coefficient of expansion, which is a constant (.003665). t — the observed temperature. 316 APPENDIX. The formula is obtained as follows : — With reference to the correction of the given volume for temperature : l+at : I :: V1 : V V1 V = - i+at and for pressure : V1 V : —— : : A : 760 1 +at Y_ VxxA 76o(i+ae) Example. — Suppose the volume of gas to be corrected for temperature and pressure, i.e., V1 = 30 cc, the observed barometric pressure, i.e., ^ = 740 mm., and the temperature of the room, i.e., £=15° C, then the required volume will be : y_ 30><740 = 22200 _2 6cc 760(1 +.003665) 801.78200 i.e., 30 cc. of a gas at 740 mm. pressure and 150 C. are reduced to 27.6 cc. at standard pressure and temperatui'e (760 mm, and o° C). INDEX. Aberration — Chromatic, 277. ,, spherical, 277. Absorption-bands. 45. Accommodation, 278. line of, 282. Aceto-acetic acid, 137. Aceton, 137. Achroo-dextrin, 20, 68. Acid-albumin, 8, 72. Acid-lnematin, 49. Acidulated brine, 130. Acme sacchar-ureameter, 137. Actiou-current of muscle, 207. ,, nerve, 209. Acuity of vision, 285. Adamkiewicz, reaction of, 3. iEsthesiometer, 304. After-images, 300. After-load, 181. Albumenoids, 13. Albumin, 1. ,, coagulation temperature of, 4. ,, derived, 7. egg, 4. „ general reactions, 2. „ native, 4. „ nitrogen in, 3. „ serum, 5. „ soluble, 4. „ sulphur in, 3. „ vegetable, 92. Albumin — Estimation of, 131. „ in urine, 128. „ tests for, 129. Albuminometer, 131. Albuminuria, 128. Albumoses, 10, 73. Albumosuria, 131. Alkali-albumin, 7. Alkali-ha.'iiiatin, 49. „ reduced, 50. Alkaline phosphates. I Amalgamation of zinc, 14s1. ,, mixture. 148. Amido-caproic acid, 15. Ammonium carbouate, 315. urate, 140. Ainyl nitrite, 251. Amyloid substance, 10. Amyloses, 17. Analysis of a fluid, 31. Animal starch, 20. Anode, 148. Anti-group, 73. Apex-preparation, 237. Apnoaa, 264. Apparent movements. 292. Aromatic compounds, 312. Artificial eye, 293, 303. „ gastric juice. 69. ,, pancreatic juice, 76. Aristotle's experiment, 304. Astigmatism, 282. Atropin on heart. 233. Auto-laryngoscopy, "270. Auxocardia, 248. Barford's solution, 22. Baryta mixture. 113. Benzoic acid, 124. Benzo-purpurin. 75. Bergmann's experiment, 2S6. Bezold's experiment, 27S. Bichromate cell, 14D. Biedermann's modification, 213. Bile, 82. „ acids. S3. „ action of, „ cholesterin in, 84. „ crystallised, S3. ,, Gmelin's test, 84. ,, in urine. 133. ,, Pettenkofer's test, 83. 3i3 INDEX. Bile, pigments, 84. „ salts, 84. Bile-acids in urine, 133. Bile-pigments in urine, 133. Bilin, 82. Bilirubin, 84. Biliverdin. 84. Binocular contrast, 300. „ vision, 289. Biuret reaction, 2, 111. Black's experiment, 266. Blind spot, 283. Blood, 33. ,, action of saline solution, 34. ,, Buchanan's experiments, 39. ,, clot, 35. ,, coagulation of, 34, 35. ,, defibrinated, 36. ., grape-sugar in, 40. ,, laky, 33. ,, mammalian, 35. ,, plasma, 35. ,, reaction, 33. ,, red corpuscles of, 34. ,, serum of, 35. ,, specific gravity of, 34. ,, stains, 57. ,, transparent. 33. Blood in urine. 132. Blood-corpuscles, 42. „ numeration of, 42. Blood-gases, 267. Blood-pressure, 257. „ tracings, 260. Bone, 30. Bbttger's test, 22. Bowditch's rotating spiral, 156. Bread, 93. Break extra- current, 160. Break-shock, 159. Brine test, 130. Briicke's method for glycogen, Brush electrodes, 208. Buchanan's experiments, Buffy coat. 35. Burette, 107. 39. Calcic phosphate, 106. Calculi urinary, 140, 143. Cane-sugar, 24. ,, inversion of, 24. Cannula, 261. Capillaries, pressure in, 256. Capillary electrometer, 209. Carbohydrates, 16, 310. Carbohydrates, classification of, 17. ,, general characters, 17. , , rotatory power, 28. Carbon-oxide haemoglobin, 48. ,, spectrum of, 56. Cardiograph, 244. Casein, 7. Cathode, 148. Cellulose, 20. Chemical stimulation, 166. Chloral, 273. Cholesterin, 84, 86. Cholic acid, 83. Ch.ond.rin, 14. Chondrogen, 14. Choroidal illumination, 299. Christison's formula, 99. Chromatic aberration, 277. Chromo-cytometer, 60. Chronograph, 187. Ciliary motion, 162. Circulation, scheme of, 253. ,, microscopic examina- tion of, 256. Circumpolarisation, 25. Clerk-Maxwell's experiment, 285. Coagulation of blood, 34. „ action of neutral salts, 35. ,, experiments, 39. Cold — Effects on blood, 35. ,, ,, heart, 226. „ ,, muscle, 190. Cold spots, 305. Collagen, 13. Colloid, 19. Colorimetric method, 63. Colour-blindness, 296. „ sensations, 295. Coloured fringes, 277. ,, shadows, 299. Combined sulphuric acid, 104. Commutator, 153. Congo-red, 75. Constant current, 149, 169, 182, 220. Contact key, 152. ,, sense of, 306. Contraction — Paradoxical, 212. ,, secondary, 211. ,, without metals, 210. Contrast, 296. „ binocular, 300. Crank-myograph. 181. Curare, 172, 175, 220. Curdling of milk, 91. IXDEX. 319 Currents of rest, 207, 209. Cystin, 142. Daniell's cell, 147. Darby's fluid meat, 9. D'Arsonval's N. P. electrodes, 20S. Defibrinated blood, 36. Deglutition apncea, 265. Demarcation currents, 205, 209. Deposits — organised, 139. ,, unorganised, 140. ,, urinary, 139. Depressor nerve, 259. Deprez's signal, 187, 1S8. Detector, 149. Dextrin, 20. ,, varieties of, 23. Dextrose, 21. ,, reducing power of, 69. ,, rotatory power of, 25. Diabetes, 134. Dialyser, 74. Diffusion, 277. Digestion — Biliary, 85. ,, gastric, 69. ,, pancreatic, 76. ,, salivary, 67. Diplopia nionophthalmica, 283. Direct stimulation, 171. ,, vision, 285. Direction, judgment of, 291. Disaccharides, 17. Distance, judgment of, 291. Donne's test, 139. Du Bois electrodes, 158. ,, induction coil, 155. ,, key, 152. ,, rheochord, 154. Dupi-e's apparatus, 115. Duration of impressions, 287. Dynamometers, 171. Earthy phosphates, 105. Egg-albumin, 2, 4. Elasticity of artery, 193. lungs, 264. ,, muscle, 193. Elastin, 14. Electrical keys — Contact, 152. ,, Du Bois, 150. ,, mercury, 152. ,, Morse, 152. plug, 152. ,, spring, 152. ,, trigger, 152. Electrical stimuli, 165. Electrodes, 156, 157. brush, 208. ,, for nerve, 209. ,, non-polarisable, 205. Electrometer, 209. Electro -motive phenomena of muscle, 205. Electro - nn itive phenomena of heart, 209. Electro - motive phenomena of electrotonic variation, 215. Electrotonus, 213. Ellis' air piston recorder, 251. Emulsion, 29, 80. Endocardial pressure, 237. Enuelmann's experiment, 220. Enzymes, 73. Erdmann's float, 109. Ergograph, 196. Ervtlno-dextrin, 20. Esbach's albuminometer, 131. Examination of a fluid, 145. ,, ,, solid, 145. Excitability, muscular. 172. Exhaustion in nerve and muscle, 196. Experimentum mirabile, 276. Expired air, 266. Extensibility of muscle, 192. Extra-current, 160. Far point, 280. Faradic electricity, 155. Fatigue of muscle, 194. Fats, neutral, 29. Fehling's solution, 134, 135. Ferments— Milk curdling, 74, SO, 91. ,, pancreatic, 77. ,, pepsin, 70. ,, pytalin, 67. ,, rennet, 74. trypsin, 77. ,, in urine, 127. Fibrin, 8, 36. Fibrin-ferment. 39. Fibrinogen, 6, 39. Fibrinoplastin, 37. Field of vision, 288. Flour, 92. Fractional heat-coagulation, 11. Furfurol, 112. Gad's experiment, 29. Call stones. 84. Galvanic electricity, 149. ,, ,, to graduate, 153. ,20 INDEX. Galvani's experiment, 210. Galvanometer, 203. Galvanoscope, 149. Garrod's test, 122. Gas-sphygmoscope, 251. Gases in blood, 267. Gaskell's clamp, 238. ,, method, 231. Gastric action on milk, 73. ,, digestion, 70. ,, juice, 69. ,, peptones, 73. ,, products of, 71. Gelatin, 13. Gerrard's apparatus, 117. Globulins, 6. Globulinuria, 130. Glucose, 21. , , in blood, 40. ,, to prepare, 23. , , rotatory power of, 25. Glucoses, 17. Gluten, 92. Glycerin, 29. Glyein, 97. Glyco-cholic acid, 82. Glycogen, 20, 86. ,, preparation of, 87. ,, tests for, 88. Glycosamin, 96. Glycosuria, 134. Gmelin's test, 84, 133. Gracilis, experiment on, 220. Grape-sugar, 21. Grove's cell, 148. Guaiacum test, 132. Guanin, 97. Hsematin, 50. ,, preparation of, 56. , Hsematinometer, 48. Hsematoporphyrin, 52. Hiematoscope, 48. Hsematuria, 132. Heemin, 56. Hsemochromogen, 50. Haeniocytometer, 42. Haemoglobin, 34. ,, ash of, 41. ,, carbonic oxide, 48. ,, crystals of, 43. ,, estimation of, 63. ,, nitrites on, 51. ,, non-diffusibility, 34. oxy-, 34. ozone test, 44. Haemoglobin, preparation of, 63. ,, reduced, 46. , , spectrum of, 45. Hsemoglobinometer, 57. Hemoglobinuria, 132. Hremometer, 59. Hand-electrodes, 156. Haser-Trapp's coefficient, 99. Haploscope, 301. Hearing, 307. Heart — Action of drugs on, 233. apex, 237. ,, atropin on, 233. ,, constant current on, 233. ,, current, 209. ,, effect of swallowing on, 249. ,, endocardial pressure, 237. ,, excised, 221. ,, frog's, 220. ,, inhibition of, 247. ,, inhibitory centre, 228. ,, lever, 239. ,, mammal's, 242. ,, motor centres, 229. ,, movements of, 223. ,, nicotin on, 233. ,, perfusion, 235. ,, pilocarpin on, 233. ,, record of, 224. ,, reflex inhibition, 247. ,, section of, 222. ,, sounds of, 243. ,, staircase of, 234. ,, Stannius's experiment, 228. ,, sympathetic on, 232. ,, effect of temperature on, 222, 226. ., tonometer, 240. ,, tortoise's, 227. vagus on, 229, 262. . , valves of, 242. Heat — Effect on cilia, 162. heart 222 „ ,, muscle, 190. Heller's test, 129. Helmholtz's modification, 161. Hemialbumose, 10, 11, 72, 73. Heywood's experiment, 267. Hippuric acid, 123, 124. Holmgren's worsteds, 296. Hot spots, 305. Hiifner's apparatus, 116. Hydrocele fluid, 39. Hydrochinon, 98. Hydrostatic test, 264. INDEX. 321 Hypobromite method, 114. Hypobromite of soda, 112, 116. Image, formation of, 276. Impressions, duration of, 287. Indican, 126. Indigo-forming substance, 126. Indirect stimulation, 171. ,, vision, 285. Indol, 79, 81. Induced electricity, 155. Induction apparatus, 155. „ new form of, 156. „ graduated form of, 156. Inflammation, 256. Inhibition, 276. Interrupted current, 160, 168, 182. Intra-pleural pressure, 267. Intra-thoracic pressure, 265. Inverted image, 276 In vert- sugar, 24 Iodine solution, 19. Irradiation, 289. Judgment of direction, 291. „ of distance, 291. of size, 290. Keratin, 14. Key -Du Bois-Keymond's, 15<). „ mercury, 152. „ Morse, 152. „ plug, 152. „ spring or contact, 152. „ trigger, 152. Kjeldahl's method, 119. Knee-jerk, 273, Koenig's flames, 270. Kreatin, 15, 95. Kreatinin, 15, 95. 124. Kiihne's — Curare experiment, 220. ,, experiment, 212. eye, 29.S. ,, gracilis experiment, 219. ,, muscle-) ire--. 212. ,, pancreas powder, 77. Kiilz's method for glycogen, 87- Kymograph, 257. Lactic acid, 75. Lactoscope, 92. Lactose, 23, 90. Lambert's method, 295. Lardacein, 10. Laryngoscope, 268. Latent period, IS.'!. Laurent's polarimeter, 25. Lecithin, 96. Legal's test, 138. Leucin, 15, 16, 78. Lieben's test, 137. Lieberkiihn's jelly. 7. Liebermann's reaction, 3. Li< big's extract of meat, 95. Liquor pancreaticus, 77. ,, pepticus, 70. Liver, extracts of, 88. Load, 191. Locality, sense of, 304. Lungs, elasticity of, 264. Lustre, 301. Lymph-hearts. 257. Magnesia mixture, 106. Magnetic tuning-fork, 199. Malt extract, 68. Maltose, 23, 67. ,, reducing power, 69. Marey's tambour, 200. Marriotte's experiment, 283. Maximal contraction, 180. Maxwell's experiment, 285. Meat, extract of, 95. Mechanical stimulation, 166. Meiocardia, 248. Mercurial key, 152. Metaphosphoric acid, 1 30. Methreniogiobin, 51, 52. Methyl violet, 75. Metronome, 199. Micro-spectroscopes, 65. Milk, 89. ,, casein of, 90. ,, curdling of, 91. ,, fat of, 90. ,, gastric juice on, 73. ,, opacity of, 92. ,, pancreatic juice on, 81. ,, to peptonise, 81. ,, rennet on, 74, 91. ,, salts of, 91. , , souring of, 90. Milk-curdling ferment, 80. Milk-sugar, 23, 90. Millon's reagent, 2. Mineral v. organic acids, 74. Minimal contraction, 179. Mohr's test, 75. Moist chamber, 177. Molisch's test, 22. Monosaccharides, 1 7. X 322 INDEX. Moore's test, 21, 134. Morse key, 152. Mosso's ergograph, 196. Mucin, 14. Mucus in urine, 126. Mulberry calculus, 143. Midler's valves, 266. Murexide test, 15, 121. Muscse volitantes, 287. Muscarin, 233. Muscle — Action current of, 207. ,, action of heat, 190. ,, „ ver atria, 191. ,, curve of, 185. , , demarcation current, 205. ,, direct stimulation of, 171. effect of load, 191. ,, ,, two shocks, 201. ,, elasticity, 192. , , electrical stimulation, 167. ,, excitability 172. ,, exhaustion of, 196. ,, extensibility of, 193. ,, extractives of, 94. , , extracts of, 94. ,, fatigue, 194. , , independent excitability, of, 172. ., indirect stimulation of, 171. ,, plasma of, 95. ,, press, 212. ,, reaction of, 93. ,, rupturing strain, 171. ,, single contraction, 168. ,, sound, 171. ,, stimulation of, 166. ,, tetanus, 197. ,, thickening of, 200. ,, work of, 180. Muscular contraction, 190. ,, load on, 191. ,, temperature on, 190. ,, veratria on, 191. Muscular sense, 306. Myographs, 177. ,, crank, 181. ,, Frederick's, 189. „ Marey's, 188. Pfliiger's, 195. ,, pendulum, 182. spring, 184. Myelin -forms, 96. Myosin, 6. Native albumins, 4. Neef's hammer, 155. Negative variation, 207. After-images, 300. Nerves — Action current, 209. „ demarcation current, 209. „ double conduction, 219. „ exhaustion of, 196. „ unequal excitability, 217. „ velocity of energy, 218. Nerve-muscle preparation, 162, 164. Neuramcebometer, 275. Nicotin on heart, 233. Nitrates, 51. , , in saliva, 66. Nitrogen, estimates of, 119. Non - polarisable electrodes, 150, 205. Normal saline, 164. „ soda solution, 103. Nuclein, 96. Oils, chemistry of, 29. Ophthalmoscope, 302. Organic acids, 74. Ossein, 30. Oxalate of lime, 143. Oxy-hsemoglobin, 45. ,, crystals of, 44. „ reduction of, 48. „ spectrum of, 53. Pancreatic digestion, 76. „ extracts, 77. „ juice, 76. „ action on fats, 80. ,, „ on proteids, 77. „ „ on starch, 77. ,, milk, 81. „ peptones, 78. Paradoxical contraction, 212. Paraglobulin, 37. Pea-meal, 93. Pendulum myograph, 182. Pepsin, 70. Peptones, 9, 72. ,, diffusibility of, 10. Witte's, 11. Peptonum siccum, 11. Peptonuria, 131. Perfusion, 235. Perimetry, 288. Peripheral projection, 305. Perrin's eye, 303. Pettenkofer's test, 83, 133. Prl user's law of contraction, 216. INDEX. Phakoscope, 281. Phenol, 126. ,, tests for, 138. Phenyl-hydrazin test, 22, 135. „ maltosazon, 23. Phloro-glucin vanillin, 75. Phosphenes, 286. Phosphoric acid, 107. „ volumetric process for, 107. Picric acid, 130. Picro-carmine, spectrum of, 52. Picro-saccharimeter, 136. Pigments of bile, 84. ,, urine, 125. ,, reactions for, 126. Pilocarpin on heart, 233. Pince myographique, 200. Piston-recorder, 236. Pitting, 161. Plasma of blood, 35. Plattner's bile, 83. Plethysmography 251. Plug key, 152. Pohl's commutator, 153, 173. Poisons on heart, 233. ,, on muscle, 191. ,, on spinal cord, 273. Polarimeters, 25. Polarisation of electrodes, 158. Polaristrobometer, 27. Polygraph, 244, 263. Polysaccharides, 17. Positive after-images, 300. Potassic bromide, 273. ,, chloride, 273. ,, sulphocyanide, 66. Potassio-mercuric iodide, 88. Preformed sulphuric acid, 104. Pressure sense, 305. Proteids, 1. ,, classification of, 4. ,, coagulated, 9. ,, general reactions, 2. ,, non-diftusibility, 3. ,, rotatory power, 28. Ptvalin, 77. Pulse, 248. Pulse-wave, 253. Pupil, 283. Purkinje's figures, 286. ,, Sanson's images, 280. Pus, 139. Putrefactive products, 79. Pvrocatechin, 13S. Pyuria, 139. Quantitative estimation of chlo- rides, 104. Quantitative estimation of phos- phates, 107. Quantitative estimation of sugar, 135. Quantitative estimation of urea, 113, 114. Quantitative estimation of uric- acid, 127. Radial movement, 292. Ragona Scina, 299. Reaction, biuret, 2. ,, of Adamkiewicz, 3. ,, of Liebermann, 3. ,, of Uffelmann, 75. ,, xanthoproteic, 2. Reaction-time, 275. Recording apparatus, 175. Reduced alkali-ha?matin, 49. ,, haemoglobin, 48. ,, ,, spectrum of, 55. Reflex action, 271. Rennet, 74. ,, ferment, 91. Respiration, voluntary, 265. Respiratory movements, 262. Retinal shadows, 286. Reverser, 155. Rheochord, 153, 154. Rheometer, 255. Rheonom, 170. Rheoscopic frog, 21 1. 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MEDICINE AND THE ALLIED SCIENCES. 9 GRIFFIN (John Joseph, F.CS.) : CHEMICAL RECREATIONS: A Popular Manual of Experimental Chemistry. With 540 Engravings of Apparatus. Tenth Edition. Crown 4to. Cloth. Part I. — Elementary Chemistry, 2/. Part II. — The Chemistry of the Non-Metallic Elements, including a Comprehensive Course of Class Experiments, 10/6. Or, complete in one volume, cloth, gilt top, . . 12/6. HAD DON (A. C„ M.A., F.Z.S., Professor of Zoology at the Royal College of Science, Dublin) : AN INTRODUCTION TO THE STUDY OF EMBRYOLOGY, for the use of Students. With 190 Illustrations. In Royal 8vo, Cloth, 18s. " An excellent Resume of recext research, well adapted for self-study. . . . Gives remarkably good accounts (including a'.l recent work) of the development of the heart and other organs. . . . The book is handsomely got up." — Lancet. " Prof. Haddox has the real scientific spirit for work of this kind. . . . The development of the various organs ably demonstrated. . . . 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STIRLING, M.D., Sc.D., BRACKENBURY PROFESSOR OF PHYSIOLOGY IN OWENS COLLEGE, AND VICTORIA UNIVERSITY, MANCHESTER ; EXAMINER IN THE UNIVERSITIES OF OXFORD AND CAMBRIDGE. Royal 8vo, Handsome Cloth. 34s. WXify bztx) UnmeratTS Illustrations. THIRD ENGLISH EDITION. GENERAL CONTENTS. Part I. — Physiology of the Blood, Circulation, Respiration, Digestion, Absorption, Animal Heat, Metabolic Phenomena of the Body. Part II.— Secretion of Urine : Structure of the Skin ; Physiolog}' of the Motor Apparatus ; the Voice and Speech ; General Physiology of the Nerves ; Electro-Physiology ; the Brain ; Organs of Vision, Hearing, Smell, Taste, Touch ; Physiology of Development. *#* Since its first appearance in 1880, Prof. Landois' Text- Book of Physiology has been translated into three Foreign languages, and passed through five large editions. To meet the wishes of Students, the Third English Edition has been issued in One Volume, printed on specially prepared paper. Numerous Additions have been made throughout, bringing the work abreast in all respects of the latest researches in Physiology and their bearing on Practical Medicine; and the number of Illustrations has also been largely increased — from 494 in the First to 692 in the present Edition. " So great are the advantages offered by Prof. Landois' Text-book, from the exhaustive and eminently practical manner in which the subject is treated, that it has passed through four large editions in the same number of years. . . . Dr. Stirling's annotations have materially added to the value of the work. Admirably adapted for the Practitioner. . . . With this Text-book at command, no Student could fail in his examination." — TJie Lancet. "One of the most practical works on Physiology ever written, forming a 'bridge' between Physiology and Practical Medicine. . . . Its chief merits are its completeness and conciseness. . . . The additions by the Editor are able and judicious. . . . 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" Unquestionably the most admirable exposition of the relations of Human Physiology to Practical Medicine that has ever been laid before English readers." — Students' Journal. MEDICINE AND THE ALLIED SCIENCES. n By Drs. MEYER and FERGUS. Now Beady, with Three Coloured Plates and numerous Illustrations. Royal Svo, Handsome Cloth, 25s. DISEASES OF THE EYE (A PRACTICAL TREATISE ON), By EDOUARD MEYER, •Prof, a VEcole Pratique de la Faculte" de Medecine de Paris, C/iev. of the Leg. of Honour, etc. Translated from the Third French Edition, with Additions as contained in the Fourth German Edition, By F. FERGUS, M.B., Ophthalmic Surgeon, Glasgow Infirmary. The particular features that will most commend Dr. AEeyer's work to English readers are — its conciseness, its helpfulness in explana- tion, and the practicality of its directions. 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Here we find discussed the origin, the extinction, succession, migration, persistence, distribution, relation, and variation of species — with other considerations, such as the Identification of Strata by Fossils, Homotaxis, Local Faunas, Natural History Provinces, and the relation of Living to Extinct forms." — Dr. Henry Woodward, F.R.S., in the " Geological Magazine.'1'' "A deeply interesting volume, dealing with Physical Geology as a whole, and also presenting us with an animated summary of the leading doctrines and facts of Palaeontology, as looked at from a modern standpoint." — Scotsman. " Professor Seeley's work includes one of the most satisfactory Treatises on Lithology in the English language. ... So much that is not accessible in other works is presented in this volume, that no Student of Geology can afford to be without it." — American foza-nal of Engineering. " Geology from the point of view of Evolution." — Westminster Review. " Professor Seeley's Physical Geology is full of instructive matter, whilst the philosophical spirit which it displays will charm many a reader. From early days the author gave evidence of a powerful and eminently original genius. No one has shown more convincingly than the author that, in all ways, the past contains within itself the interpretation of the existing world. " — Annals of Natural History. SCIENTIFIC AND TECHNICAL WOBKS. 19 Demy 8vo, Handsome cloth, 34s> Stratigraphical Geology and Paleontology, ON THE BASIS OF PHILLIPS. BY ROBERT ETHERIDGE, F. R. S., THE NATURAL HIST. DEPARTMENT, BRITISH MUSEUM, LATE PAL/EONTOLOGIST TO 1 GEOLOGICAL SURVEY OF GREAT BRITAIN, PAST PRESIDENT OF THE GEOLOGICAL SOCIETY, ETC. TOtb tfftap, numerous tables, ano GbirtE-sir. flMates. "In 1854 Prof. John Morris published the Second Edition of his 'Catalogue of British Fossils,' then numbering 1,280 genera and 4.000 species. 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Must take HIGH RANK AMONG WORKS OF REFERENCE." — AtketUeUttt. 20 CHARLES GRIFFIN & CO.'S PUBLICATIONS. SCIENTIFIC MANUALS BY W. J. MACQUORN RANKINE, C.E., LLD„ F.R.S., Late Regius Professor of Civil Engineering in the University of Glasgow. Thoroughly Revised by W. J. MILLAR, C.E., Secretary to the Institute of Engineers and Shipbuilders in Scotland. In Crown 8vo. Cloth. L RANKINE (Prof.): APPLIED MECHANICS: comprising the Principles of Statics and Cinematics, and Theory of Struc- tures, Mechanism, and Machines. With numerous Diagrams. Twelfth Edition , 12/6. " Cannot fail to be adopted as a text-book. . . . The whole of the information is so admirably arranged that there is every facility for reference." — Mining J ournal. II. RANKINE (Prof.): CIVIL ENGINEERING: comprising Engineering Surveys, Earthwork, Foundations, Masonry, Carpentry, Metal-work, Roads, Railways, Canals, Rivers, Water-works, Harbours, &c. With numerous Tables and Illustrations. Seventeenth Edition, 16/. 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RANKINE (Prof.): USEFUL RULES and TABLES for Engineers and others. With Appendix : Tables, Tests, and Formula for the use of Electrical Engineers ; comprising Submarine Electrical Engineering, Electric Lighting, and Transmission of Power. By Andrew J amieson, C. E. , F. R. S. E. Seventh Edition, 10/6. "Undoubtedly the most useful collection of engineering data hitherto produced." — Mining Journal. " Every Electrician will consult it with profit." — Engineering, VI. RANKINE (Prof.): A MECHANICAL TEXT-BOOK, by Prof. Macquorn Rankine and E. F. Bamber, C.E. With numerous Illustrations. Third Edition, 9/ '. " The work, as a whole, is very complete, and likely to prove invaluable for furnishing a useful and reliable outline of the subjects treated of." — Mining Journal. *** The Mechanical Text-Book forms a simple introduction to Professor Rankine's Series of Manuals on Engineering and Mechanics. SCIENTIFIC AND TECHNICAL WORKS. 21 Prof. Rankine's Works— {Continued). VII. RANKINE (Prof.): MISCELLANEOUS SCIENTIFIC PAPERS. Royal 8vo. Cloth, 31 6. Part I. Papers relating to Temperature, Elasticity, and Expansion of Vapours, Liquids, and Solids. Part II. Papers on Energy and its Trans- formations. Part III. Papers on Wave- Forms, Propulsion of Vessels, &c. With Memoir by Professor Tait, M. A. Edited by W. J. Millar, C.E. With fine Portrait on Steel, Plates, and Diagrams. " Xo more enduring Memorial of Professor Rankine could be devised than the publica- tion of these papers in an accessible form. . . . The Collection is most valuable on account of the nature of his discoveries, and the beauty and completeness of his analysis. . . . The Volume exceeds in importance any work in the same department published in our time." — Architect. By SIB EDWAED REED. Royal 8uo, Handsome Cloth, 25s. THE STABILITY OF SHIPS. EY SIR EDWARD J. REED, K.C.B., F.R.S., M.P., KNIGHT OF THE IMPERIAL ORDERS OF ST. 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The work also embodies a very full account of the historical rise and progress of the Stability question, setting forth the results of the labours of Bouguer, Bernoulli, Don d'Ulloa, Euler, Chapman, and Rom.me, together with those of our own Countrymen, Atwood, Moseley, and a number of others. The mcdem developments of the subject, both home and foreign, are likewise treated with much fulness, and brought down to the very latest date, so as to include the labours net only of Dakgnies, Reech (whose famous Mimoire, hitherto a sealed book to the majority of English na%-al architects, has been reproduced in the present work), Risbec, Ferranty, Dupin, Guyou, and Day.mard, in France, but also those of Rankine, Woolley, Elgar, John, White, Gray, Denny, Inglis, and Benjamin, in Great Britain. In order to render the work complete for the purposes of the Shipbuilder, whether at home or abroad, the Methods of Calculation introduced by Mr. F. K. Barnes, Mr. Gray, M. Reech, M. 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In it the Student, new to the subject, will find the path prepared for him, and all difficulties explained with the utmost care and accuracy ; the Ship-draughtsman will find all the methods of calculation at present in use fully explained and illustrated, and accompanied by the Tables and Forms employed ; the Shipowner will find the variations in the Stability of Ships due to differences in forms and dimensions fully discussed, and the devices by which the state of his ships under all conditions may be graphically represented and easily understood ; the Naval Architect will find brought together and ready to his hand, a mass of information which he would other- wise have to seek in an almost endless variety of publications, and some of which he would possibly not be able to obtain at all elsewhere." — Steanishif. 22 CHARLES GRIFFIN & CO.'S PUBLICATIONS. Medium 8vo, Handsome eloth, 25s. HYDRAULIC POWER AND . HYDRAULIC MACHINERY. BY HENRY ROBINSON, M. Inst. 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A full Prospectus of the above important work — giving a description of the Plates — may be had on application to the Publishers. SCIENTIFIC AND TECHNICAL WORKS. 23 SCHWACKHOFER and BROWNE: FUEL AND WATER: A Manual for Users of Steam and Water. By Prof. FRANZ SCHWACKHOFER of Vienna, and WALTER R. BROWNE, M.A., C.E., late Fellow of Trinity College, Cambridge. Demy 8vo, with Numerous Illustrations, 9/. "The Section on Heat is one of the best and most lucid ever written."— Engineer. " Contains a vast amount of useful knowledge. . . . Cannot fail to be valuable to thousands compelled to use steam power." — Railway Engineer. " Its practical utility is beyond question." — Mining Journal. SEATON (A. E., Lecturer on Marine Engineering at the Royal Naval College, Greenwich, and Member of the Institute of Naval Architects) : A MANUAL OF MARINE ENGINEERING; Comprising the Designing, Construction, and Working of Marine Machinery. With numerous Illustrations. Eighth Edition. Demy 8vo. Cloth, 18/. 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Crown Svo. Cloth, 7/6. " The Mechanic's Guide will answer its purpose as completely as a whole series of elaborate text-books." — Mining Journal. TRAILL (Thomas W., F.E.R.N., M.Inst.C.E., Engineer-Surveyor-in-Chief to the Board of Trade): BOILERS: THEIR CONSTRUCTION AND STRENGTH. A Handbook of Rules, Formulae, and Tables for the Construction of Boilers ; Safety- Valves ; Material for Boilers ; Tables of Areas, &c. Arranged for the Use of Steam-Users. Second Edition, Revised and Enlarged. Pocket-Size, Leather, 12s.; also for Office-Use, Cloth, 12s. *** In the New Issue the subject matter has been considerably extended ; Tables have been added for Pressures up to sco lb. per square inch, and some of the Table have been altered, besides which new ones and other matter have been introduced, which have been specially prepared and computed for the Second Edition'. "Contains an enormous quantity of information — to be had nowhere else— arranged in a very convenient form. It is admirably printed, and retlects credit on the Publishers." Engineer. " Will prove a welcome and valuable addition to the literature of the subject. . . . We can strongly recommend Mr. Traill's book as being the most complete, eminently practical, and most recent work on Boilers." — Marine Engineer. "Will prove invaluable to the Engineer and Practical Boiler-maker."— Prac tical Engineer. 2( CHARLES GRIFFIN <£• CO.'S PUBLICATIONS. OFFICIAL YEAR-BOOK OF THE SCIENTIFIC AND LEARNED SOCIETIES OF GREAT BRITAIN AND IRELAND. Price 7/6. COMPILED FROM OFFICIAL SOURCES. SEVENTH ANNUAL ISSUE. Comprising {together with other Official Information) LISTS of the PAPERS read during 1889 before the ROYAL SOCIETIES of LONDON and EDINBURGH, the ROYAL DUBLIN SOCIETY, the BRITISH ASSOCIATION, and all the LEADING SOCIETIES throughout the Kingdom engaged in the following Departments of Research : — I 1. 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