Medico-physical works; being a translation of Tractatus quinque medico-physici

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SS MEDICO-PHYSICAL

=C\J

?co

WORKS

OF

JOHN MAYOW, LL,D., M D.

(1674)

Blcnibtc iliab ir?ep*iirr.
No. 17.

AaM-^

Blembic Club IReprints— IRo. 17

MEDICO-PHYSICAL WORKS

BEING A TRANSLATION OF

TRACTATUS QUI N QUE MEDICO-

PHYSICI

BY

JOHN MAYOW, LL.D., M.D.

(1674)

c^^^

}EJ)(nburQb:
Published by THE ALEMBIC CLUB

Edinburgh Agent:
JAMES THIN, 54 and 55 SOUTH BRIDGE

London Agents :
SIMPKIN, MARSHALL, HAMILTON, KENT & CO., LTD.

1907

Printed by Oliver and Boyd, Edinburgh

PREFACE

•" John Mayow, descended from a genteel family of
his name, living at Bree, in Cornwall, was born in the
parish of St Dunstan's in the West, in Fleet Street,
London," in May 1643. His father's name was
William and his mother's EHzabeth. He was
received as a commoner of Wadham College, Oxford,
on 3rd April 1658, and admitted a scholar on 23rd
September 1659. Upon the recommendation of
Henry Coventry, one of the Secretaries of State and a
former fellow of the college, he was elected to a
fellowship at All Souls' College on 3rd November
i66o. He graduated B.C.L. on 30th May 1665 and
D.C.L. on 5th July 1670. He also "studied physic,
and became noted for his practice therein, especially
in the summer time, in the city of Bath." He died
*^ in an apothecary's house, bearing the sign of the
Anchor, in York Street, near Covent Garden, within
the liberty of Westminster ... in the month of
September 1679, and was buried in the Church of
St Paul, Covent Garden."

These particulars, derived from Wood's Athencs
Oxonienses^ 1722, and the notice by Hartog in the
Dictionary of National Biography^ convey practi-
cally all we have been able to find as to the personal
history of Mayow. On 30th November 1678 he was

iv Preface

elected a Fellow of the Royal Society of London^
having been proposed by Hooke.

His philosophical writings consist of five treatises^
written in Latin. Two of these —

De respiratione ; and
De rachiiide
— were first published at Oxford in 1668. A revised
edition of these two, together with the other three —
De sal-nitro et spiritit nitro-aereo ;
De respiratione foetus in utero et ovo ; and
De moiu miisciilari et spiritibus animalihiis
— was published at Oxford in 1674.

Mayow was thus twenty-five years old when he
published his tracts on respiration and on rickets^
and he died at the early age of thirty-six.

Mayow's works were not much noticed in his own
time, and speedily fell into almost total oblivion^
Hales, in his Vegetable Staticks (London, 1727), being
the only author who refers to his writings in the
earlier part of the eighteenth century. They were
reprinted in Latin at the Hague in 1681 and at
Geneva in 1685. A German translation appeared at
Jena in 1799 and a French translation at Paris in
1840.

After the great revolution in chemical theory which
followed the discovery of oxygen, Mayow's book was
discovered in old libraries, where it had remained
disregarded for a hundred years ; and those who
discovered it were astonished to see that the new
chemistry, which was rapidly conquering the scientific
world, was to be found in this old book. As far as we
know, Dr Thomas Beddoes was the first distinctly to-
recognise Mayow's claim. Dr Beddoes published his
discovery of Mayow in a letter to Dr Edmund
Goodwyn, with an Analysis of Mayow'' s Chemical

Preface v

Opinions. It is dated Oxford, 12th February 1790,
two years before his resignation of the readership in
chemistry. Besides Beddoes we have Dr J. B. A.
Scherer, physician in Vienna, who in 1793 pubHshed
Beweis^ dass J. Mayow vor 100 Jahren den Grimd
ziir antiphlogistischen Chemie und Physiologie gelegt
hat^ and also G. D. Yeats, M.B. of Hertford College,
Oxford, physician at Bedford, who in 1798 published
Observations on the Claims of the Moderns to some
Discoveries in Chemistry and Physiology.

Beddoes quotes from Blumenbach's Institutiones
Physiologicce^ 1787, the following remarkable
passage : " Magna jam pars memorabilium horum
phsenomenorum," says he, speaking of respiration,
^'quibus nuperis lustris et physica de aeribus factitiis
disciplina et physiologia negotii respirationis tarn
egregie ditata et illustrata est, jam ante centum et
quod excurrit annos innotuit acutissimi ingenii
medico Joanni Mayow, cujus de sal-nitro et spiritu
nitro-aereo (quo nempe nomine dephlogisticatum
aerem insignivit) tractatum, Oxon. 8vo editum,
magna cum voluptate legi et relegi."

But these attempts to make Mayow and his work
known to the scientific and medical world were not
crowned with much success.

Mayow is indeed mentioned, and his work is
discussed, in most books on the History of Chemistry ;
but as far as we have been able to discover, not many
chemists or physiologists have made anything like an
intimate personal acquaintance with his writings.
Quite recently a considerable part of the treatise on
nitre has been translated into German and published
by Prof. Donnan (Ostwald's Klassiker der exakten
Wisse^ischaften, Nr. 125, 1901). We had begun the
translation some time previously, but soon saw that it

vi Preface

was not possible to obtain a clear idea of Mayow's
scientific position without reading the whole of the
five treatises. We therefore now present to the
reader a translation of Mayow's Opera omnia. Our
rule has been to translate as literally as possible,
avoiding the use of any words or phrases which have,
since Mayow's time, acquired a special scientific
meaning. This has led to the retention of expres-
sions not now familiar to scientific readers. Some of
these we may here note. Sulphur is often used for
what may be called the combustible principle, and
sulphureous matter almost always means combustible
matter, without any suggestion that it contains
sulphur in the sense we should mean if we used the
phrase now. There is no difficulty in seeing quite
clearly when Mayow uses the word sulphur in the
general and when in the special sense.

By *' purely saline salt" he means an alkali, fixed or
volatile, usually a carbonate ; and " fixed salt " means
potash or soda, usually as carbonate. It is scarcely
necessary to say that the nature of the difference
between the caustic and the mild alkalis was not
discovered till nearly a hundred years after Mayow's
time.

We have confined ourselves to the work of transla-
tion and have added nothing in the way of commen-
tary or criticism ; but it may be well to remind the
reader that Hooke's Micrographia had been published
shortly before Mayow wrote, and that most of Boyle's
treatises appeared shortly after.

The edition of Mayow's works printed at Oxford
in 1674 has been used in the preparation of the
translation.

A. C. B.
L. D.

TABLE OF CONTENTS

FIRST TREATISE.— ON SAL NITRUM
AND NITRO-AERIAL SPIRIT.

CHAPTER I.— On Sal Nitrum.

Air is impregnated with vital and igneous salt, p. i. The
history of nitre, p. i. It is composed of a purely saline salt,
alkaline or volatile, and of an acid salt, p. 2. But contains
no sulphur, p. 2. These constituents of nitre are evinced
by its analysis, p. 2. As also by its formation, p. 2. How-
nitre is produced in the earth, p. 3. The air contributes
something to its formation, p. 3. Nitre does not come
wholly, but only in part, from the air, p. 3. The alkaline
salt, of which nitre partly consists, comes from the earth, p.
4. Answer to an objection, p. 5. The seeds of the alkaline
salt exist in the earth, p. 5. What would seem to be the
macrocosmic seed of the earth, p. 5. Earth seems to be
composed of fixed salt and sulphur intimately united, p. 6.

CHAPTER II.— Of the A£rial and Igneous Part
OF THE Spirit of Nitre.

Whence the spirit or acid salt of nitre arises, p. 7.
Whether it springs from the air, p. 7. The spirit of nitre
does not entirely, but only in part, come from the air, p. 8.
Something aerial is altogether necessary for the production
of fire, p. 8 ; see pp. 70 and 71. The aerial pabulum of fire is
shown not to be the air itself, p. 9 ; see pp. 77 and 82. Nor
is it nitre in its totality, p. 9. Igneo-aerial particles exist
in nitre, p. 9. Nitre mixed with sulphur can be kindled
vii

viii Contents

under water and in a place free from air, p. 9. The flame of
nitre is produced by the igneo-aerial particles contained in
it, p. 10. But not by sulphureous particles, as nitre does
not contain such, p. 10. For the production of flame
sulphureous and igneo-aerial particles are required, p. 11.
Sulphureous matter cannot be set on fire without aerial
pabulum, p. 11. Why, for the kindling of nitre, it is not so
much air, as sulphureous matter, that is required, p. 11.
Why the flame of nitre is so impetuous, p. 12. The access
of external air promotes the kindling of nitre, p. 12. The
igneo-aerial particles contained in nitre seem to constitute its
aerial part, p. 13 ; see pp. 82 and 83. The aerial and igneous
part of nitre exists in the spirit of nitre, p. 13. The spirit of
nitre is compound, derived partly from terrestrial matter, but
also partly from the air, p. 13. Why the igneous particles of
air should be called nitro-aerial spirit, p. 14. The caustic
character of the spirit of nitre arises from its aerial part,
namely, from its igneo-aerial particles, p. 14. Why that
spirit, in distillation, appears of a ruddy colour, p. 14.
Why spirit of nitre does not go on fire although it contains
igneous particles, p. 14.

CHAPTER III.— Of the Nature of Nitro-A£rial
AND Igneous Spirit.

It is shown that the igneo-aerial spirit is of a nitro-saline
character, p. 16. Yet the igneo-aerial salt is neither acid
nor alkaline, p. 16, The form of flame chiefly depends on
the nitro-aerial particles, p. 16. It can be produced from a
certain kind of particles only, p. 17. What part the sulphu-
reous particles take in the production of fire, p. 17. What is
the essence of fire, p. 18. The caustic nature of spirit of nitre
and of flame arises from the same igneo-aerial particles, p. 18.
Why we think of the sulphureous rather than of the aerial
particles as burning, p. 19. It is shown by experiments that fire
is especially produced by nitro-aerial particles, p. 19. On the
fire produced by the rays of the sun concentrated by means
of a mirror, p. 20. Why antimony calcined by the solar
rays becomes diaphoretic and increases in weight, p. 20.

Contents ix

In what the fixation of antimony consists, p. 21. How, in
the opinion of the author, antimony can best be fixed, p. 21.
How fires protect the air from contagion, p. 22.

CHAPTER IV. — Of the Source of Acid Liquids.
Also, of the Terrestrial Part of the Spirit
OF Nitre.

Spirit of nitre is composed, in part, of an earthy matter,
p. 23. How the spirit of sulphur is produced, p. 23. It
does not exist in the substance of sulphur before it is set on
fire, pp. 23 and 163. Sulphur is endued with an alkaline
rather than an acid salt, p. 24. The spirit of sulphur seems
to be produced by its deflagration, p. 24. How the saline
particles of sulphur are liquefied, p. 25. The flame of
sulphur is very different from other fires, p. 25. Why it
is blue, p. 25. Its flame is less caustic than common flame,
p. 25. That the oil of vitriol at last distilled seems to be
formed by the action of fire, p. 26. Why the distillation
of vitriol can be continued so long, p. 26. Acid liquids
distilled from wood seem to be formed by the power of fire,
p. 27. As also the acid spirit of sugar and of honey, p.
27. How it is that colcothar exposed to air is anew
impregnated with spirit of vitriol, p. 28. Spirit of vitriol is
produced by fermentation set up by air, p. 28. On the cause
of rust, p. 29. How liquors become sour, p. 29. How spirit
of nitre is formed, p. 30. Nitro-aerial particles exist in
acid liquids, p. 31. Why there is such a close resemblance
between all acid liquids, p. 31. On the origin of nitre in the
earth, p. 32. Why contrary salts effervesce when mixed,
p. 32. Earth is impregnated with nitrous salt, but not with
fixed salt, p. 32. Why nitre is chiefly formed in saline-sul-
phureous soil, p. 32. The constituents of nitre reviewed, p. 33.

CHAPTER v.— Of Nitro-Aerial Spirit, so far as
fermentations leading to the birth or death
of things are caused by it.

How fermentation is excited in the earth, p. 34. On the
elementary principles of things \ and first on mercury, p. 34.

X Contents

Mercury and spirit are to be regarded as the same element,
p. 34. On sulphur, p. 35. Mercury and sulphur are
mutually hostile, p. 35. On salt, p. 35. On water and earth,
pp. 35 and 36. On the mutual action of the said elements,
p. 36. The aerial mercury is fixed in the embrace of salt,
p. 36. Sulphur freed from association with salt attains a
condition of volatility, p. 37. But is fixed when united with
it, p. 37. On the origin of vegetables, pp. 37 and 38. Why
nitre is especially formed in spring, p. 38. Why substances
containing salt and sulphur make land fertile, p. 38. Vege-
tables contain nitrous salt, but not purely saline salt, p. 39.
But by the deflagration of vegetables it becomes lixivial, p. 39.
Why vegetables, when calcined with a subdued flame, yield
more salt than otherwise, p. 39. Diuretic salts ought not to
be calcined with violent heat, p. 40. Why the smoke of
kindled coals causes suffocation, p. 40. Why fermenting
liquors become somewhat acid, p. 40. Why some vegetables
yield only a little fixed salt, p. 41. The nitre contained in
vegetables promotes their combustion, p. 41. On the
fermentation which causes the destruction of vegetables, p.
41. Fire is the most destructive fermentation, p. 42. There
is a close resemblance between fire and other fermentations
tending to the destruction of things, p. 43. How things are
corrupted by extraneous heat and moisture, p. 44. What is
the nature of ferments, p. 45. All heat seems to arise from
nitro-aerial particles set in motion, p. 45. Why things
become acid in fermenting, p. 46.

CHAPTER VI.— Of Nitro-Aerial Spirit, in so far
as it produces rigidity in bodies and the
Power of Resilience. Also, on the Cause of
Elasticity. Incidentally, on the Breaking of
Glass Drops.

Nitro-aerial particles fixed in things make them hard,
p. 47. Sparks struck from iron seem to catch fire from the
nitro-aerial particles contained in them, p. 48. On the
hardness of frozen water, p. 49. The cooling quality of nitre
seems to come from the nitro-aerial particles, p. 49. Why

Contents xi

water that has been boiled freezes more quickly when
exposed to cold, p. 49. How frost fertilises the earth, p. 50.
Why water dilates when frozen, p. 50. Why water is so
suitable for extinguishing fire, p. 51. Why spirituous liquors
never freeze, p. 51. Of the cause of elasticity, p. 52. On
the various ways in which rigid bodies can be bent, p. 52.
Perfectly rigid bodies cannot have their superficies either
lengthened or shortened, p. 54. Whence that arises, p. 55.
The convex side of a rigid body is carried towards the con-
cave side in the process of bending, p. 55. The matter of
the bent rigid body suffers compression, p. 56. Why, when
a rigid body is too much bent, it breaks in the middle, p. 56.
Why very solid bodies cannot be bent, p. 56. On the
manner in which bodies not so perfectly rigid bend, p. 57.
A certain rule which always holds good in natural effort to
accomplish anything, p. 57. Why it is that the thinner rigid
bodies are, so much the more easily can they be bent, p. 58.
The author's views as to the motion of restitution, p. 60.
Motion is set up by impulse alone, p. 61. Inanimate things
never begin to move spontaneously, p. 61. A certain subtle
mobile matter is always to be supposed, p. 61. The elastic
force of rigid bodies seems to arise from the impulse of
subtle matter, p, 61. Why a cord violently stretched con-
tracts spontaneously, p. 63. On the wonderful fracture of
glass drops, p. 63. Why fused glass becomes more con-
tracted in the process of cooling, p. 64.

CHAPTER VII.— That the Elastic Power of Air is
DUE TO Nitro-Aerial Spirit. Also, of the
Manner in which Air is Impregnated anew with
Nitro-AErial Particles. Incidentally, of the
Elements of Fire and of Cold.

Air is eminently elastic, p. 67. Why the skin rises into a
cupping-glass applied to it with a flame, p. 67. The elastic
force of air is diminished by burning, p. 68. That is proved
by experiments, pp. 68-71. wSomething aerial is required for
producing flame, p. 71. The air given out from the lungs of
animals has been in part deprived of elastic particles, p. 71.

xii Contents

As is shown by experiments, p. 72. To what extent the
elastic force of air is diminished by the respiration of
animals, p. 73. The entrance of air into the blood is proved,
pp. 73-74. By what sort of channels the air has to be trans-
mitted into the blood, p. 74. Fire and life are sustained by
the same aerial particles, p. 75. Difficulties raised as to
what has been said, p. ^^. In how many ways the elastic
power of bodies may arise, p. 78. It is shown that the aerial
particles are composite, p. 79. And that they are hard, p.
So. Why water is more penetrating than air, p. 80. How
air loses elasticity by the deflagration of flame, p. 80. How
fire is kindled, p. 81. The igneous and vital particles of the
air are not the air itself but only the more subtle part of it,
p. 82. It is shown that not the air itself, but only the
igneous part of it is a constituent of nitre, p. 84. The
igneous particles are simil^arly present in air and in nitre, p.
54. Why an animal and a lamp shut up in a glass from
which air is excluded quickly expire, p. 84. Air unfit for
sustaining life and fire expands in a vacuum just like un-
injured air, p. 85. Why air always comes to the flame, p. 86.
Air given out from the lungs of animals has become lighter,
p. 86. Admiration of divine providence, p. 88. How nitro-
aerial particles can be restored to air which has been
deprived of them, p. 89. The element of fire is deposited in
the sun, p. 89. The celestial fires seem to burn without the
help of sulphureous particles, p. 89. On the element of cold,
p. 90. Why the sky appears blue, p. 91. How aerial
particles acquire elastic force, p. 91. On their figure, p. 92.
And their downward movement, p. 92. Why the north wind
comes from above, p. 93. The cause of the circulation of
the air, p. 93.

CHAPTER VI 1 1.— Of Nitro-A£rial Spirit, in so far

AS IT IS BREATHED BY ANIMALS.

The nitro-aerial particles are transported into the mass of
the blood, p. 93. Air mixed with the fermenting particles of
substances loses elasticity, p. 94. The heating of contrary
salts when they effervesce together seems to depend upon

Contents xiii

aerial particles, p. 99. The vapour given off from fermenting'
substances does not seem to be air, p. 100. How inspired
air loses its elastic force, p. loi. On the use of the inspired
spirit, p. loi. The fermentation of the blood is produced by
it, p. loi. The blood is compared to the soil of a field, p,
102. Why arterial blood is brighter and redder than venous^
p. 102. The heat of the blood depends on the inspired air^
p. 104. Why animals become so hot in violent exercise, p.
105. Answers to various objections to what has been said,
p. 105. Contrary salts do not seem to effervesce more in a
vacuum than in open air, p. 106. When mixed together in a
vacuum they do not become so hot as otherwise, p. 107,
" The vital flame" and the "anima lucida" of Dr Willis dis-
cussed, p. 108. Whence fevers arise, p. 109. How the mass
of the blood degenerates into an acid liquid, p. no. It is
imbued with an acid-saline salt, p. no. Urine is also-
impregnated with such a salt, p. no. On other uses of the
inspired air, p. no.

CHAPTER IX. — Whether Air can be Generated-

Anew.

An experiment in which air seems to be produced, p. in.
How we can ascertain how much elastic force any particular
kind of air possesses, p. 113. The vapour produced in the
way described tends to expand exactly like common air, p.
115. And yet it does not seem to be air, p. 116. Because it
is not fit to support life, p. 117.

CHAPTER X.— How Fire is Propagated. Also, whv
Flame rises to a Point.

Natural operations are carried on by means of very small
things, p. 120. Ignited particles are agitated with an elastic
impulse, p. 120. Natural fermentations are excited by the
blow of subtle matter, p. 121. Fire is the greatest fermenta-
tion, p. 122. Why every flame ends in a sharp point, p. 122.
Why a flame about to go out is last seen at the top of the
wick, p. 123. Why a flame once kindled does not continue
to burn, p. 123. The sulphureous particles are volatilised in.
the flame, p. 124. What soot is, p. 124.

xiv Contents

CHAPTER XL— Of the A£rial Vortex, or Ascent
OF Sea- Water. Anglice : A Spout.

Description of the said phenomenon, p. 125. It is caused
by a whirling motion of the air, p. 127.

CHAPTER xn.— Of Light and Colours.

Light does not consist of emanations from the luminous
body, p. 134. But of a certain impulse, p. 136. The
medium, by the impulse of which the rays of light are pro-
pagated, seems to consist of nitro-aerial particles, p. 136.
Whence comes the Hght of the glow- worm,- p. 137. Colours
and the images of things do not seem to be produced by
reflected light, p. 139. But by the impulse of a pecuHar
medium, p. 141. On the colour of glittering white, p. 144.
On white colour, p. 145. Why things which are black are
more easily burned by solar rays collected by means of a
mirror, p. 146.

CHAPTER XIIL— Of Lightning.

Lightning does not seem to arise from kindled exhalations,
p. 147. How thunder is produced, p. 148. Lightning seems
to consist of nitro-aerial particles thrown into motion, p. 149.
In what way very sultry weather can be produced by unequal
motion of the air, p. 149. Whence the force of lightning
arises, p. 150. Why a thunderbolt sometimes fuses a sword,
leaving the sheath intact, p. 151. On the cause of death of
animals struck by lightning, p. 152. On violent winds
accompanying thunderstorms, p. 152.

CHAPTER XIV. — Of the Heat of Quicklime.
Incidentally, of the Combination of Opposite
Salts.

The heat of quicklime moistened with water does not
seem to arise from igneous particles simply fixed in it, p.
154. But from the heat produced by contrary salts, p. 154.

Contents xv

Alkaline salt is shown to exist in quicklime, p. 154. Also
an acid salt, p. 155. Why quicklime does not become hot
when it is wet with spirit of wine or with any sulphureous
liquid, p. 156. Whence the contrary salts of lime arise, p.
157. Why these salts of quicklime do not effervesce unless
it is wet with water, p. 158. Why the contrary salts con-
tained in the water in which quicklime has been slaked do
not mutually destroy each other completely, p. 160. Of the
combination of contrary salts, p. 160. When they are mixed
they do not completely destroy each other, p. 160. The
spirit of nitre is shown to be a volatile acid salt, p. 161.
How a kind of vitriolated tartar can be produced from
nitre, p. 162. Acid salts seek union with metals, p. 162.
Alkaline salt combines with sulphur, p. 162. It is shown that
there is no acid salt in sulphur, p. 163. Salts of different
kinds should not rashly be included in the same prescription,
p. 164. The contrary salts of quicklime will not enter into
a closer union, p. 165. In what case contrary salts can come
together without the production of any ebullition, p. 167.
Why liquids become turbid by reason of precipitation taking
place in them, p. 168, Why quicklime added to lye makes
it more sharp, p. 169.

CHAPTER XV.— Of the Thermal Waters of Bath.
Incidentally, of the Source of Springs.

On the constituents of the said hot springs, p. 170. They
are charged with salts of an acid-saline character, p. 171.
It is shown that there is no nitre in the said hot springs,
p. 171. Nor is there sulphur dissolved in their water, p.
171. Not only so, but the water does not dissolve sulphur
when boiled with it, p. 172. Nor do these hot springs con-
tain sal armoniac, p. 173. Whether vitriol is contained in
the water or not, p. 174. It contains some metallic mineral
which, on the addition of an acid, is converted into vitriol,
p. 174. Whence comes the heat of the hot springs, p. 175.
It does not seem to have its origin in subterranean fire, p.
175. Biit from fermentation excited in the depths of the
earth, p. 175. On the origin of springs, p. 175. They do

xvi Contents

not seem to come from the sea, p. 175. But from rain-water,
p. 176. How an artificial spring can be made, p. 177. Why
a saline-sulphureous mineral becomes hot when exposed to
moist air, 177. Air is lodged in the pores of water, p. 177.
Fishes draw air from the water, p. 179. On the air con-
tained in the swimming-bladder of fishes, p. 179. The heat
of the hot springs depends on air, p. 180. Why spring- water
is a little warm, p. 182. Why soap will not mix with it, p.
182.

SECOND TREATISE.— 01^ RES-
PIRATION.

The explanation of the entrance of air into the lungs, p.
183. It is not from fear of a vacuum, p. 183. Nor because
the air is pushed forward by the dilating chest, p. 184.
The inflation of the lungs depends on the pressure of the
atmosphere, p. 184. In what way it can be brought about
by the elastic force of the air, p. 185. Whence the elastic
force of the air arises, p. 186 ; see Treatise i, Chapter VII.,
p. 67. The inflation of the lungs illustrated by examples, p.
186. The lungs cannot expand themselves spontaneously,
p. 187. Why, when the thorax is perforated, the lungs
protrude from its cavity, p. 188. In what way the lungs are
inflated when the chest is wounded, p. 189. How wounds
of the chest should be closed, p. 189. How the chest is
dilated, p. 190. The external and also the internal inter-
costal muscles act in dilating the chest, p. 190. Why the
said muscles are inserted obhquely into the ribs, p. 192.
Why in dead bodies the thorax is always contracted, p. 193.
The ribs are connected to the spine by a double articulation,
p. 194. These articulations contribute to the dilatation of the
chest, p. 194. Why the ribs are joined to the sternum by
means of cartilages, p. 195. The diaphragm contributes to
the dilatation of the chest, p. 195 ; see Treatise 4, Chapter
VII., p. 287. On various ways in which respiration may
suffer, p. 196. On the so-called broken-windedness of
horses, p. 197. On orthopnoea, p. 197. On uterine suffoca-

Contents xvii

tion, p. 197. On various asthmatic paroxysms, p. 198.
Why respiration is sometimes accompanied by a whistling-
sound, p. 198. On hiccup, p. 199. On nightmare, p. 200.
How expiration is produced, p. 201. The abdominal
muscles contribute, p. 201. How laughter is effected, p.
201, On the use of respiration, p. 202. The inspired air
does not serve to cool the heart, p. 202. Nor is its sole
purpose to transmit the blood through the lungs, p. 203.
Nor the comminution of the blood, p. 204. The vital
particles of the air seem to be of a nitro-saline character, p.
205 ; see Treatise i, Chapter VH., p. 67. On the use of
the inspired spirit, p. 205 ; see Treatise i, Chapter VHI.,
p. 93 ; and Treatise 4, Chapter IV., p. 244. It is shown
that there is no ferment in the heart, p. 206. In what life
consists, p. 208. The inspired air contributes to animal
motion, p. 208 ; see Treatise 4, Chapter IV., p, 244. How
that takes place, p. 208. Why suppression of respira-
tion causes death, p. 209. Why in violent movements
animals breathe more intensely, p. 209. Insects cannot
bear want of air, p. 210.

THIRD TREATISE.— O^ THE RESPIRA-
TION OF THE FCETUS IN THE
UTERUS AND IN THE EGG.

How it is that the foetus can live in the uterus without
air, p. 211. How the uterine cry and suction in the uterus
are produced, p. 212. The nutritious juice of the uterus
takes the place of respiration, p. 21 3. The umbihcal arteries
are formed for the purpose of respiration, p. 213. They are
not destined for the nutrition of the secundines only, p. 213.
Nor for the concoction of food, p. 214 Nor do the said
arteries bring back from the embryo the cruder portions of
the nutritious juice, p. 215. Nor are they made for setting
up the circulation of the blood, p. 215. The author's opinion
as to their use, p. 216. The nutritious juice of the uterus is

b

xviii Contents

full of nitro-aerial particles, p. 216. And the same of the
seminal liquors of the ^%%^ p. 216. How the blood of the
embryo is impregnated with aerial spirit in the umbilical
vessels, p. 217. The necessity of the umbilical arteries is
proved, p. 217. Of the respiration of the chick in the ^%%^
p. 218. It is carried on by means of the umbilical vessels,
p. 218. How that takes place, p. 218. The warmth excited
in the ^g% seems to contribute towards taking the place of
respiration, p. 220. How the foetus just born and still
enclosed in its membranes can live without respiration, p.
221. On the cavity situated at the blunter end of every ^%%^
p. 222. The air contained in it does not contribute to the
respiration of the chick, p. 223. That air is conspicuously
elastic, p. 223. By incubation the liquors of the ^gg
come to occupy a smaller space than they did before, p. 224.
In how many ways the .condensation of bodies may take
place, p. 224. How the liquors of the ^%% are condensed, p.
225. On the use of the air contained in the q%%^ pp. 226,
227,

FOURTH TREATISE.— O^ MUSCULAR
MOTION.

CHAPTER I.— Examination OF the Various Opinions
OF Authors as to the way in which Muscles
Contract.

The nitro-aerial spirit contributes something to animal
motion, p. 229. The opinion of Dr Willis as to muscular
contraction is discussed, p. 230. And criticised, p. 231.
The contracted muscle draws itself together, p. 231. Dr
Steno's opinion as to the cause of muscular contraction is
examined, p. 233. The influx of new matter is required for
the contraction of muscles, p. 234. A muscle can be
shortened by a change of its shape without contraction of
its fibres, p. 234.

Contents xix

CHAPTER II.— A SHORT Description of Muscles.
Also, What part of a Muscle Primarily Con-
tracts.

On the fleshy fibres of muscles, p. 235. Description of
the fibrils, p. 235. They seem primarily to undergo con-
traction, p. 236. The oblique position of the fibres is less
fit for the contraction of the muscle, p. 236. But the posi-
tion of the fibrils is fitted for this, p. 236. The muscle is
drawn together by the contraction of the fibrils, p. 237.
The fibrils are eminently suited for producing the contrac-
tion of the muscle, p. 237.

CHAPTER III.— Of the Particles by means of
WHICH Muscular Contraction is Effected ; and,

IN THE first place, ON THE MOTIVE PARTICLES

Brought by the Blood. Incidentally, of the
Structure and Use of Muscular Flesh.

The contraction of a muscle is partly produced by the
animal spirits, p. 239. Also partly by certain particles
supplied by the blood, p. 239. The contraction of the
muscles promotes the motion of the blood, p. 239. For
what end that takes place, p. 239. The muscular flesh
seems destined for the secretion of motive particles from the
blood, p. 240. How the blood passes through the muscles,
p. 240. It does not seem to be extravasated, p. 240. It
is probable that the arteries and the veins are connected
with each other by certain special vessels, p. 241. On the
ruddy sediment of muscular flesh, p. 242. The motive
particles supplied by the blood seem to have a saline-sul-
phureous character, p. 242. Why animals become lean by
working, p. 243.

CHAPTER IV.— The Animal Spirits by which
Muscular Contraction is Produced consist of
NiTRO-AERiAL Particles. Incidentally, as to
THE Motion of the Brain.

Why the respiration is so much increased in violent
movements, p. 244. This does not take place in order that

XX Contents

a greater quantity of blood may be sent through the lungs,
p. 244. Nor for the cooling of the heart, p. 245. But
because the nitro-aerial spirits are used up in the contraction
of the muscles, p. 245. Muscular contraction is produced
by the mutual effervescence of particles of different kinds,
p. 245. Of what sort they are, p. 246. The motive effer-
vescence does not seem to arise from repugnant salts, p. 246.
But from the mutual agitation of nitro-aerial and saline-
sulphureous particles, p. 247. Why exercise makes animals
hot, p. 248. Why sweat is salt, p. 249. It is shown that
nitro-aerial particles are indeed the animal spirits, p. 250.
They do not seem to consist of volatile salt, p. 251. The
enormous amount of the air is alone equal to the supply
of the expended animal spirits, p. 252. On the respiration
of insects, p. 253. Why parts cut off from them continue to
live, p. 254, Why in insects the branches of the tracheae
terminate in the spinal marrow, p. 254. Why animals fall
into convulsions when deprived of air, p. 255. Whence it is
that strength is so much reduced in phthisis, p. 255. Why
the brain is disturbed in malignant fever, p. 255. Why we
necessarily shut our eyes when we sleep, p. 256. How light-
ning dissipates the animal spirits, p. 257. Why animals
breathe more intensely for some time after violent move-
ments, p. 257, Why blood drawn during convulsive
paroxysms quickly coagulates, p. 258. Answer to an objec-
tion brought against the hypothesis stated above, p. 258.
The sensitive soul does not seem to consist of a congeries
of animal spirits, p. 259. A conjecture about the sensitive
soul, p. 259. On the pulsation of the brain, p. 260. For
what end it takes place, p. 260. The respiration of the
brain explained, p. 260. Diverse effects are produced in
the body in accordance with the varying contraction of the
meninges, p. 260. Sneezing depends on their motion, p. 261.
How epilepsy and apoplexy may arise from disordered
motion of the dura mater, p. 261. Why oil of amber and
the like are of use in these diseases, p. 261. Sleep seems to
be caused by the interrupted motion of the meninges, p. 262.
Why hard work and watching bring it on, p. 262. The natural
functions are better carried on in sleep, p. 263.

Contents xxi

CHAPTER v.— Of the Ferments of the Stomach,
THE Pancreas, and the Spleen. Incidentally,
OF Diseases which have Reference to the
Animal Spirits.

The ferment of the stomach does not seem to be an acid
liquor, p. 264. How steel dissolves in the stomach just as
in an acid liquor, p. 264. The digestion of food is chiefly
effected by the animal spirits, p. 265. The saliva assists in
the digestion of food, p. 267. On the origin of hunger, p.
267. The bile is destined for the fermentation of the chyme,
p. 267. Of the ferment of the pancreas, p. 267. It also
serves for the digestion of food, p. 268. The pancreatic
juice does not seem to be acid, p. 268. Of the use of the
spleen, p. 269. The nitro-aerial spirits pass through the
brain in a continuous stream, p. 270. There must be some
vessels that bring them from the brain, p. 270. There seems
to be a threefold use of the spleen, p. 271. Why such
plexus of nerves are to be found in the abdomen, p. 271.
Whence arise hypochondriac flatus and eructations, p. 271.
Why the spleen is florid in infants and not dark as in adults,
p. 272. Whence arises the fermentation of the spleen, p. 274.
How dropsy can be produced by scirrhus of the spleen, p. 274.
In what way black bile is produced, p. 275. The spleen
consists of two kinds of vessels, p. 275. From the various
obstruction of these vessels different diseases arise, p. 276.
How an animal can live when its spleen has been entirely
removed, p. 276. How the fixed salts of the food are
volatilised in the mass of the blood, p. 277. The spleen
seems to help towards that end, p. 277. Of the diseases
which concern the animal spirits, p. 278. On phthisis, p.
278. On apoplexy and paralysis, p. 279. On epilepsy and
intoxication, p. 279. On the cause of inflammable sputum,
p. 279. On melancholia and mania, p. 280. That indisposi-
tion to move may arise from disorder of the muscular flesh,
p. 280. Also the spontaneous lassitude of scorbutus and of
jaundice, p. 280. Convulsive cramps of the tendons may
arise from the same cause, p. 281. How exercise favours
health, p. 281.

Contents

CHAPTER VI.— Of the Mode in which the Fibrils
Contract. Also, of the Motion of Contracting

Muscles.

The fibrils seem to be shortened by their contortion, p.
282. That is made plain by an example, p. 282. How
nitro-aerial spirit contracts the fibrils, p. 283. Why muscles
struck by lightning become hard, p. 284. Of the motion of
contracting muscles, p. 284. The contraction takes place
towards the more fixed end of the muscle, p. 285. Muscles
sometimes contract towards their insertion, p. 286. On the
contraction of sphincters, p. 286.

CHAPTER vn. — Of . THE Contraction of the
Diaphragm. Also, of the Pulsation of the
Heart. Incidentally, of its Palpitation. Also,
OF THE Motion of Animals when they raise
themselves aloft.

The diaphragm in its contraction is carried downwards
and outwards, p. 288. It never in inspiration descends
below the plane, p. 288. But sometimes in expiration, when
the chest is wounded, it becomes convex towards the
intestines, p. 289. Of the pulsation of the heart, p. 290.
Why the heart in systole strikes the left side of the chest,
p. 290. How the blood is expelled from the heart, p. 292.
The contraction of the right ventricle contributes to the
constriction of the left ventricle, p. 293. Whence palpitation
of the heart arises, p. 294. A noteworthy case of this, p.
295. How the detention of the blood in the lungs causes
asthma, p. 297. How jumping is produced, p. 298. The
opinion of Dr Willis on this subject is refuted, p. 298. It is
produced by the contraction of the extensor muscles, p. 299.
The impressed force of projectiles is nothing but motion,
p. 300-

Contents xxiii

FIFTH TREATISE.— O^ RICKETS.

When and where this disease made its first attack, p.
303. Only infants suffer from it, p. 304. At what time it
attacks them, p. 304. The symptoms of this disease
reviewed, p. 304. On its cause, p. 305. It does not consist
in a vitiated state of the blood, p. 305. Nor in a depraved
constitution of the parts, p. 305. The nerves contribute to
the nutrition of the body, p. 306. This disease arises from
lack of nervous supply, p. 307. The brain does not suffer in
this disease, p. 307. But the spinal marrow does, p. 307.
The cause of the symptoms of this disease, and first of the
excessive growth of the head, p. 307. Second of the swelling
of the abdomen, p. 308. Third of the strumous glands, p.
309. Fourth of the curvature of the bones, p. 310.
Examination of Dr Glisson's opinion on this subject, p. 310.
Statement of the author's opinion, p. 312. On the curvature
of the spine, p. 313. Why the chest is pointed, p. 314. On
the prognosis of the disease, p. 316. Method of treatment,
p. 317. Chief indications, p. 317. Use of enemata and
some examples, p. 318. What sort of vomits are suitable,
p. 319. Examples of cathartics, p. 319. On surgical treat-
ment, p. 320. Specific alteratives, p. 322. Caution as
to the use of steel, p. 325 Diaphoretics and the use of
the bath, p. 325. Of the symptoms, and first of diarrhoea,
p. 326. Of excessive sweating, p. 326. Of difficult dentition,
p. 326. On external remedies, p. 327, etc.

ERRATUM

p. 206, line 15 from bottom^*?/- "beat" read "beats."

ON SAL NITRUM AND NITRO-
AERIAL SPIRIT

CHAPTER I

ON SAL NITRUM

THAT this air surrounding us, which from its
tenuity escapes the glance of the eye, and
appears as a void to those who survey it, is impreg-
nated with a universal salt of a nitro-saline nature,
that is to say, with a vital, igneous, and highly fer-
mentative spirit, will be obvious, I conceive, from
what follows. But in order that this nitro-aerial salt
may be more clearly understood, I think that we
should begin with a history of nitre.

I am not unaware that there are already many
treatises on nitre, and that there is scarcely one of
our recent authors who has not written something
about it ; as if, indeed, it were ruled by fate that this
wonderful salt should make no less noise in philosophy
than in war, and fill the universe with its sound. Yet,
meanwhile, the truth seems to be quite obscured by
the multitude of writers, and even now nitre lies hid
in darkness. But in order to set forth our views on a
matter so recondite, let us examine briefly, according
to our custom, of what elements nitre is composed,
and, indeed, from what family it originates.

With regard then to the constituent elements of

A

2 Mayow

nitre, sal nitrum seems to be composed of an extremely
fiery acid salt, and, in addition, of an alkali or of purely
saline volatile salt taking the place of the sal alkali.
And this may be ascertained not only from its analysis
but also from the way in which it is produced. As
regards sulphur, which nitre is commonly supposed to
contain, it is our opinion that although nitre defla-
grates readily enough when thrown into the fire,
still a combustible sulphur is in no wise present, as
will be shown below.

If nitre is analysed by distillation, acid spirit will
pass into the receiver, while fixed nitre, closely re-
sembling sal alkali^ will be left in the retort. More-
over, when nitre is melted in a crucible, and sulphur
is thrown in repeatedly until the nitre will deflagrate
no longer, the substance left at the bottom is im-
properly called fixed nitre, since there is fixed only
one element of the nitre, namely, its salt ; the other
element, namely, the acid spirit, escaping in vapour
during deflagration. Still, this spirit may be retained
if deflagration takes place in a tubulated retort with a
receiver attached, or under a bell-jar.

Further, if nitre and tartar, mixed in equal quanti-
ties, are kindled by ignited iron or charcoal, fixed salt
equal in amount to the whole of the tartar will be
found after the deflagration, and of this at least some
part is derived from the nitre, and is generally but im-
properly called salt of tartar ; for, since this fixed salt
is equal to the whole of the tartar, while the tartar is
not all fixed salt, but consists to a large extent of spirit
and a fetid oil which passes off during the deflagra-
tion, some part of the remaining salt must accordingly
be due to the nitre.

In the same way, if we look at the mode in which
nitre is produced, we shall recognise clearly the same

I

On Sal Nitrum and Nitro- Aerial Spirit 3

constituent elements. For if the acid spirit of nitre is
poured upon any alkali, or, in place of the alkali, upon
purely saline volatile salt, from the mutual strife of
these two things coming together and the intense
action, sal nitrum is generated, which will readily
deflagrate when thrown into the fire. So that nitre
would seem to be born fit for fights and hostile
encounters, since it derives its origin from the mutual
conflict of opposing elements and from enmity
itself.

The constituents of nitre having been in this way
considered, let us next inquire how sal nitrum is
produced in the earth. For from almost any soil
impregnated by the air and the weather, but especially
from such as abounds in sulphur and fixed or volatile
salt, as that from stables, dovecots, and slaughter-
houses, sal nitrum is abundantly derived, and from
its source is well called sal terrce.

As to the mode in which nitre originates in the
earth, the generally received opinion is that the earth
as its proper matrix draws sal nitrum from the air in
virtue of its own attractive force. And, indeed, there
can be no doubt whatever that the air contributes in
no small degree to the generation of nitre, since nitre is
only evolved from soil which is impregnated with air.
Moreover, if earth from which all the nitre has been
lixiviated be exposed to the air, it will after some lapse
of time abound once more in nitre.

But, assuredly, one can scarcely suppose that the
nitre itself is all derived from the air, but merely its
more volatile and subtle part, the rest of the nitre
being due to the earth, for of the nitre obtained from
the earth, by no means the least part is a fixed salt
which is not volatilised by the very fiercest fire. For
in the distillation of nitre, only the acid spirit of

4 Mayow

the nitre is volatilised, the fixed salt being left in the
retort. And there is no ground for saying that the
nitre of the air is of a more volatile nature than ordi-
nary nitre. For if earth from which all the nitrous
salt has been lixiviated is exposed to the air, sal
niiriim^ not volatile, I say, but fixed and of the ordi-
nary sort, will after some lapse of time be produced.
Consequently, if that nitre were wholly derived from
the air, then nitre of the more fixed sort, that is,
common nitre, must reside in the air, but that such
should fly about in the very rare air is not to be sup-
posed. But you may say that the same nitre which
is volatile when flying about in the air, becomes fixed
in the earth. But I would ask how that can take
place, unless something fixed from the earth be added
to the volatile nitre of the air ? And what else is
this, but saying that the volatile part of the nitre is
derived from the air, while its more fixed part is deriv^ed
from the earth ?

To this we further add that if nitre, such as is
extracted from the earth, resided in the air, then as
the aerial nitre, whatever it be, mixes with kindled
fires (for the aerial nitre becomes food for the fire), it
would necessarily follow that every flame, even the
mild flame of a lamp, would constantly detonate on
account of the nitrous particles mixed with it ; yet
this does not take place.

From these considerations it seems to be established
that sal 7iitrum is derived partly from the air and
partly from the earth, and this will appear still clearer
from what follows.

Let us consider then, in the next place, what part
of the nitre is contributed by the earth, and, also,
what is contributed by the air. With regard to this,
it is our opinion that the fixed salt of which nitre in

071 Sal Nitriim and Nztro-Aerial Spirit 5

part consists, is derived from the earth — and for this
reason, that it cannot, as we have already indicated,
reside in the very rare air on account of its highly
fixed nature. It favours this view that from earth
impregnated with fixed or volatile salt, as from stables
and also from soil containing quicklime or ashes, sal
nitrum is lixiviated in greater abundance than from
any other soil, because these salts, united in course of
time with nitro-aerial spirit in a way to be explained
below, are converted into nitre. And, indeed, it is
probable that ashes, quicklime, and the like, fertilise
the soil, for this reason only, that they afford fixed
salt for the production of nitre, as will be shown
below.

Here, perhaps, some one will object that if earth
from which all the salts have been lixiviated is ex-
posed to the air, sal nitrum will, after some time, be
produced in it anew.

I reply that seeds of fixed salts exist, although
obscurely, in all soil, even in that which has been
lixiviated, and that these, by the force of a sort of
aerial ferment, are digested in course of time into
fixed salt, as I shall endeavour to show below. That
the earth is impregnated with a certain universal seed,
fecundating all things, has long been a received
opinion. Why, then, not suppose that this macro-
cosmic seed is either itself fixed salt or, at least, the
seeds of fixed salts hidden in the bosom of the earth ;
and that these when brought in progress of time to
maturity are, together with nitro-aerial spirit, changed
into sal nitriun. And it is a proof of this that nitre
generated in the bowels of the earth contributes in no
small degree to the growth of plants, as will be shown
below. For as metallic seeds here and there dispersed
through the mass of the earth are in the course of

6 Mayow

time converted into perfect nietals, it is in like manner
probable that seeds of fixed salts lie deep hidden in
every fertile soil as in a suitable matrix, and that they
by long digestion and the influx of air are changed
into fixed salts. For in no other way can we conceive
whence there should arise such an abundance of fixed
salts as is usually obtained by lixiviation from the
ashes of burned plants. For certainly none of these
salts can proceed from another source than the earth.
Indeed, it is probable that earth, pure and simple, is
nothing else than sulphur and fixed salt united
together in the closest bonds, and that both are held
together in so firm a union that it is only after a long
period of fermentation, set up by the air and the
weather, that they reach a state of activity. But this
will be discussed more fully below. And, at any rate,
if sulphur and fixed salt are melted by a gentle heat,
there results from their union a mixture of a dark
purple colour, very like a clod of earth — the only
difference, perhaps, being that earth is composed of
sulphur and fixed salt, both immature, and united
together by a closer bond.

On Sal Nitrum and Nitro-Aerial Spirit

CHAPTER 11

OF THE AERIAL AND IGNEOUS PART OF THE
SPIRIT OF NITRE

It is shown that the Spirit of Nitre is a compound body^ and that it is
derived partly from the air and partly from terrestrial matter.
First, of its aerial part.

In the previous chapter we treated generally of the
elements of which nitre is composed, and specially
of its more fixed part, the sal alkali^ to wit. Let us
look, in the next place, at the source of the other
element of the nitre — viz., its acid spirit. Regarding
this, I was for some time in doubt whether nitrous
spirit in a state of the finest subdivision did not reside
in the air and, fleeting to and fro and permeating all
things in virtue of its most penetrating nature, instantly
assail, whether from hate or rather from some con-
jugal affection, whatever fixed or volatile salt it at any
time encountered in its wandering path ; and whether
these two, closely united together, did not appear to
coalesce in a teriiiim qiiid^ to wit, common nitre.
And assuredly there are arguments of no little weight
which can be advanced in support of this hypothesis.
For any other source than the air for the acid spirit of
nitre is scarcely conceivable, since sal nitrtim is gener-
ated in earth which is in no way impregnated with
an acid salt. It is also to be noted that all salts what-
ever, fixed and volatile, as also vitriols, if calcined to
the complete expulsion of the acid spirits, acquire
when exposed for some time to the air a certain

8 Mayow

acidity, and become to some extent nitrous. More-
over, steel filings if exposed to moist air, are corroded
just as they would be by acid fluids, and are changed
into aperitive crocus martis. So that apparently a
certain acid and nitrous spirit resides in the air.

But when I had seriously considered the matter,
the acid spirit of nitre seemed to be too ponderous
and fixed to circulate as a whole through the very thin
air. Besides, the nitro-aerial salt, whatever it may be,
becomes food for fires, and also passes into the blood
of animals by means of respiration, as will be shown
below. But the acid spirit of nitre, being humid and
extremely corrosive, is fitted rather for extinguishing
flame and the life of animals, than for sustaining them.

But although the spirit of nitre does not proceed
altogether from the air, still we must believe that
some part of it originates from the air. For, since
some part of the nitre is derived from the air, as has
been shown above, while the fixed salt, of which nitre
in part consists, proceeds from the earth, the remainder
of the nitre, that is to say, its acid and fiery spirit,
must be derived, in part at least, from the air. But
in order that the aerial part of the spirit of nitre may
be better understood, we must briefly premise the
following.

First, it is, I think, to be admitted that something
aerial, whatever it may be, is necessary to the pro-
duction of any flame — a fact which the experiments of
Boyle have placed beyond doubt, since it is established
by these experiments that a lighted lamp goes out
much sooner in a glass that contains no air than it
does in the same when filled with air — a clear proof
that the flame enclosed in the glass goes out, not so
much because it is choked, as some have supposed, by
its own soot, as because it is deprived of its aerial

Oil Sal Nitrum and Nitro-Aerial Spirit 9

food. For since there is more room for receiving the
smoke in the empty glass than in the glass that is full
of air, the lamp would go out in the latter sooner than
in the former, if its extinction were due to the smoke.
Besides, no sulphureous matter, if placed in a glass
from which the air has been pumped, can be kindled
either by ignited charcoal or iron, or by the solar rays
collected by means of a burning-glass ; so that there
can be no doubt whatever that certain aerial particles
are quite indispensable to the production of fire, and,
indeed, it is our opinion that these are mainly instru-
mental in the production of fire, and that the shape
of the flame is mainly dependent upon these,
thrown into extremely brisk motion, as will be ex-
plained at greater length below. But it is not to be
supposed that the air itself, but only that its more
active and subtle part is the igneo-aerial food, since a
lamp enclosed in a glass goes out when there is still
an ample enough supply of air in it, for neither is it
to be believed that the particles of air which existed
in the said glass are annihilated by the burning of the
lamp, nor yet that they are dissipated, since they are
unable to penetrate the glass. Further, it is impos-
sible that these igneo-aerial particles are any perfect
nitre, as is generally supposed — for it was already
pointed out that not the very nitre as a whole, but
only a certain part of it, resides in the air.

In the second place, it would be reasonable to suppose
that the igneous particles of air necessary to the support
of all flame reside in sal nitrum and constitute its more
active and fiery part, for it is to be noted that nitre
mixed with sulphur deflagrates readily enough in a
glass which does not contain air, and also under water,
as will be established by the following experiment ;
for let gunpowder, very finely ground, be made

10 Mayow

into a hardish mass with a little water, and let a
small tube, closed at one end, be densely filled with
it by forcibly ramming the stuff in with a stick.
Next, let that gunpowder be set on fire at the open
end of the tube, and the tube be inverted and plunged
into water, and kept there. Then the gunpowder will
deflagrate under water until it is all gone. Moreover,
that powder, arranged in the manner aforesaid, will
burn in a glass containing no air, although other fires
are presently extinguished because the aerial food is
withdrawn — a sufficiently clear proof that sal niirum
contains in itself the igneo-aerial particles necessary
to the production of flame ; so that for its deflagra-
tion there is no need for a supply of igneous particles
from the air.

That igneo-aerial particles exist in nitre is further
evident from this, that flame produced by deflagrating
nitre is caused by the igneo-aerial particles residing in
it and bursting out in a compact body with fiery
motion, but not by its sulphureous particles. For it
is probable that nitre has no sulphureous particles as
ingredients ; for I cannot agree with the famous Dr
Willis, who has stated in his treatise on Fermentation
that there is a great deal of sulphur in nitre. His
principal arguments are these — that if nitre is thrown
upon the fire it will immediately produce a flame, and
that it is especially generated in places where there
are sulphureous animal excrements. But, with all
due respect to so eminent a man, I should have
thought that nitre, pure and simple, is in no wise im-
pregnated with sulphureous particles. For neither in
the rectified spirit of nitre nor in pure sal alkali is
any combustible sulphur to be found ; and yet, from
the combination of these two, nitre will be produced.
But, because nitre produced in this manner will defla-

071 Sal Nitrum and Nitro- Aerial Spirit ii

grate, we cannot believe that this results from
sulphureous particles, for it contains none, but from
the igneo-aerial particles contained in it and thrown
into very rapid motion. And this will be made still
clearer by what follows.

For it is to be noted that for the production of any
flame, it is absolutely necessary, as has been already
pointed out, that there should be not only sulphureous
particles, but also igneo-aerial particles. To kindle
an}^ sulphureous matter, igneo-aerial particles must
be supplied, either from the air or from nitre pre-
viously added. And this is the reason why sulphur
will not take fire in a vacuum unless nitre has been
mixed with it. But, on the other hand, for the
kindling of nitre there is no need for igneo-aerial
particles to be supplied from without, because it will
deflagrate readily enough in places from which air is
excluded. But for its kindling it is quite indispens-
able that some sulphureous matter be mixed with it.
For if nitre be thrown into a heated crucible it will
not take fire. If, however, any sulphureous matter be
previously mixed with it, then the nitre, when thrown
into the said crucible, will immediately burst into
flame. Nay, nitre can in no wise be kindled by the
flame of a candle, or by the solar rays, unless sulphur
has been previously mixed with it. And yet the
same nitre if thrown upon charcoal will be easily set
on fire ; but this happens because the sulphureous
particles of the charcoal ignite it. From these con-
siderations it is undoubtedly established that nitre
has no sulphureous particles contained in it, and this
is why, for its deflagration, sulphureous particles must
be supplied from without. And hence it follows that
nitre supplies in the flame excited by it the igneo-
aerial particles only, but by no means the sulphureous

1 2 Mayow

particles, of which it is altogether destitute. And
hence it is that the flame of nitre is very different
from that which is produced by any deflagrating
sulphureous matter. For sulphureous matter burns
when igneo-aerial particles are supplied from the air^
but nitre from the igneo-aerial particles closely packed
in itself and breaking forth in densest array. Hence
it is that the flame of nitre is exceedingly impetuous.
That the form of flame depends mainly on the igneo-
aerial particles, I shall attempt to show later.

But the reason why nitre is chiefly produced in
places that are largely imbued with sulphur will be
evident from what follows.

Since this treatise was written, Boyle's experiments
recently published have come into our hands. In the
second of these it is shown that when gunpowder is
kindled, by means of a burning-glass, in a glass freed
from air, the flame is not propagated, as in other cases,
through the whole of its mass, but that only those
grains on which the collected solar rays fall take fire.
So that it appears that the access of air is necessary
even for the kindling of gunpowder. I reply that
although that powder will deflagrate by means of the
igneo-aerial particles residing in it, in a place where
there is no air, and under water, still the access of
external air contributes in no small degree to its
kindling. For it is to be noted that air, on account
of its great elastic power, lies in the closest proximity
to the sulphureous particles of the gunpowder and
even presses powerfully against them, whence it is
that when the powder is once ignited in free air
nitro-aerial particles of the air are never lacking to
keep up the flame ; while, on the other hand, the
igneo-aerial particles in gunpowder are intimately
blended with the sulphureous particles only in the in-

I

On Sal Nitriim and Nitro- Aerial Spirit 13

dividual grains, and are not carried to those that are
kindled ; so that the flame of the powder is speedily
extinguished in a vacuum, owing to a break in the
continuity of the igneo-nitrous particles. But how
greatly the elasticity of the air helps to produce fire
will be more fully established by what will be said
below.

From what has been already said, it is, I think, to
some extent proved that nitre contains in itself the
igneo-aerial particles required for the production of
flame. Wherefore, since some part of nitre is derived
from the air and igneo-aerial particles exist in it, it
seems we should affirm the proposition that the aerial
part of nitre is nothing else than its igneo-aerial
particles.

But now since the aerial part of nitre exists in its
acid spirit, but not in the fixed salt, which, as we have
already shown, forms the rest of the nitre, we may
conclude that the igneo-aerial particles of nitre ^ which
are identical with its aerial part, are hidde7i in the
spirit of nitre^ and constitute its aerial part.

Indeed, it is probable that the spirit of nitre is a
compound, and that some of its particles are flexile,
humid, and of a grosser nature, being apparently
derived from terrestrial matter — as I shall endeavour
to show below — but that other particles are rigid,
dry, and extremely subtle, agile, ethereal, and really
igneous, and yet, being united with saline particles in
a fluid and moist condition, are unfitted for entering
on a fiery movement, and that these at any rate are
derived from the air.

With regard then to the aerial part of nitrous spirit,
we maintain that it is nothing else than the igneo-
aerial particles which are quite necessary for the
production of any flame. Wherefore, let me hence-

14 Mayow

forth call the fiery particles, which occur also in air,
nitro-aerial particles or nitro-aerial spirit.

For, indeed, the spirit of nitre seems to derive its
caustic and very potent fiery nature from the nitro-
aerial and fiery particles which reside in it. So that
it is commonly, and not improperly, called potential
fire. And, indeed, when nitre mixed with sulphur is
set on fire, it is probable that the nitro-aerial particles
of this impetuous flame proceed from the nitrous
•spirit, since the fixed salt of nitre, with which the
acid spirit is combined, is very alien to the nature of
flame, and remains to a large extent at the bottom of
the crucible after the nitre has been deflagrated in it.
And, indeed, I do not know anything in nature
approaching nearer to fire than the red spirit of nitre
which passes into the receiver in the course of distilla-
tion, with a ruddy colour ; but the ruddiness of nitrous
spirit, rivalling flame, seems to be due to the igneo-
aerial particles' of the spirit, which are agitated with
an almost fiery movement. It is corroborative of this
view that the spirit of nitre is extremely corrosive,
destructive, and caustic, and possesses a very flame-like
nature. And, indeed, it is probable that the form of
flame depends largely, if not exclusively, upon nitro-
aerial particles such as are contained in the spirit of
nitre, as will be shown below.

One will readily object here that the acid spirit of
nitre is by no means combustible, for it will not, like
sulphureous matter, blaze if thrown into the fire, but,
on the contrary, it will put the fire out. I reply that
the igneo-aerial particles existing in the spirit of nitre
are in a humid condition, and that they are prevented
from beginning a fiery movement on account of being
covered over with particles of acid fluid, as we have
already intimated. And, indeed, humidity is a very

Oji Sal Nitrum and Nitro- Aerial Spirit 15

great hindrance to fire, since it is exceedingly well
adapted for extinguishing fiery particles. But although
the spirit of nitre will not deflagrate if put into a
flame, yet if it is poured upon salt of tartar, nitre will
be generated from the combination, and if this be
thrown into the fire it will immediately produce flame.
But we must suppose that the flame of this deflagrat-
ing nitre is caused by the igneo-aerial particles of the
nitrous spirit being thrown into agitation. For the
salt of tartar of which the rest of the nitre is com-
posed seems to be very alien to the nature of flame,
as we have shown above. But the reason why the
igneo-aerial particles of nitrous spirit are well adapted,
when combined with fixed salt, for producing flame,
seems to be this, that when the spirit of nitre unites
with fixed salt to form nitre, its humidity being lost,
it changes into a dry and rigid substance ; so that as
its igneo-aerial particles exist now in a dry condition,
there is no obstacle to their commencing a fiery
motion.

Further, nitro-aerial particles must, it appears, if
they are to take the form of flame, enter into close
combination with a fixed salt, or with something else
to take the place of the fixed salt ; so that they may
be torn violently and with elastic force from their
partner and thrown into a state of the most rapid
motion, as I shall endeavour to show below.

1 6 Mayow

CHAPTER III

OF THE NATURE OF NITRO-AERIAL AND IGNEOUS
SPIRIT

From what has been already said, it is, I think, to
some extent certain what the nature of the nitro-aerial
and fiery spirit is. For since the aerial and igneous
part of nitre, or what is the same thing, nitro-aerial
spirit, exists in the acid spirit of nitre and constitutes
its more active part, it follows that the nitro-aerial
and fiery spirit is of a^hitro-saline nature, and has the
character rather of an acid, than of a fixed, salt. And,
assuredly, the effects of fire seem to agree well with an
extremely subtle and highly corrosive salt, as will be
shown immediately. It must, however, be remarked
that this igneous salt is in no way hostile to fixed
salts, but, on the contrary, rather intensifies their
power than diminishes it as acid liquids do. For
fixed salts when heated in the fire become more acrid
and caustic in their nature. Certainly the acid spirit
of nitre seems to be opposed to fixed salts only as
regards its terrestrial and humid part, but not as to
its dry and fiery part. Nay, there is not so much
contrariety, I think, as is commonly supposed
between fixed salt and any acid, as will be more
fully expounded below.

But let us consider in the next place the part which
nitro-aerial spirit, or what is the same thing, the
aerial part of nitre, plays in producing fire. On this
point my opinion is that the form of flame is chiefly
due to the nitro-aerial spirit set in motion. For I do not

I

On Sal NitriLtn and Nitro- Aerial Spirit 17

think we ought to agree with recent philosophers,
who beHeve that fire can be produced by the subtle
particles of any kind of matter if they are thrown into
violent agitation. In fact, while the Peripatetics
formerly assigned a distinct quality for almost every
natural operation and multiplied entia unnecessarily,
the Neoterics on the other hand maintain that all
natural effects result from the same matter, its form
and its state of motion or of rest alone being changed,
and that consequently any thing whatever may be
obtained from any thing. But in truth this new
philosophy seems to depart too far from the doctrine
of the ancients, and I have thought it better to take
an intermediate path. It would certainly be a reason-
able supposition that certain particles of matter which
are unlike in no other respect than in the form and
extremely solid and compact contexture of their parts,
differ so much that by no natural power can they be
changed one into another, and that the Elements con-
sist of primary, and in this way peculiar, particles.
Hence, I conceive that fire can be produced only by
particles of a certain kind, and this is obvious from
the very fact that it cannot be kindled without nitro-
aerial particles.

As regards the sulphureous particles which are
also indispensable for the production of fire, the
necessity for them seems to arise merely from this
that they are naturally fit to throw nitro-aerial
particles into a state of rapid and fiery commotion.
And I think it is not impossible that fire may be pro-
duced without the presence of sulphureous particles.
The fire from the solar rays when condensed by a
burning-glass, and the other celestial fires appear to
be of this sort. For although sulphureous particles
are absolutely necessary for kindling the kitchen fire,

B

1 8 Mayow

yet I do not think they exist in celestial fires, as I
shall endeavour to show below.

For whether we consider flame as sharp, caustic,
and in the highest degree corrosive, or as possessing
an extremely penetrating and dissolving power, or
finally as being ruddy and bright, in all of which
qualities the true essence of fire consists, all these, I
say, seem to proceed from its nitro-aerial spirit, since
the particles of the latter are in the highest degree
subtle, sharp, and caustic. For it has been shown
above that the extremely corrosive and acrid nature
of nitrous spirit is due to the nitro-aerial and fiery
particles which reside in it. And, indeed, fire and
the spirit of nitre are so like in respect to their
caustic virtue, that 1t can scarcely be doubted that
their extremely corrosive nature is due to particles
of the same kind, namely, to the nitro-aerial and fiery
spirit which resides in both.

Besides, nitro-aerial particles when in very great
commotion become red like fire and glisten, as is
clearly seen in the spirit of nitre which is ruddy dur-
ing distillation. Nay, that every kind of light pro-
ceeds from the motion of the nitro-aerial particles
will be shown below ; while, on the other hand, the
gentler sulphureous particles, however violently
agitated, appear less fitted for assuming the keen
and eminently destructive nature of fire.

If we consider attentively the nature of flame and
reflect upon the character of the change which the
fiery particles undergo on being ignited, we can form
no other conception than that the kindling of the
igneous particles consists in their extremely rapid
motion. Why then should we not suppose that
saline particles are specially fit for the production of
fire ? For since they are extremely solid, subtle, and

On Sal Nitrum and Nitro- Aerial Spirit 19

agile, they seem to be much better suited for execut-
ing a swift and fiery movement than the crasser and
very soft sulphureous particles.

But the reason for the notion that it is the sul-
phureous rather than the nitro-aerial particles which
take fire is, that the grosser sulphureous nutriment of
fire is always in view, while the nitro-aerial particles
are so fine and subtle that they quite escape observa-
tion, and yet it is certain that nitro-aerial particles are
not less necessary than sulphureous particles for the
production of fire.

The following experiment confirms what has been
said, viz., if nitre be put into a hot crucible it will
soon liquefy but will not take fire, although oil will
immediately burn if thrown into the crucible. The
inference from this is that the fiery particles which
penetrate the glowing crucible are not of a sul-
phureous nature, for otherwise the nitre would be
kindled by the fiery particles mixed with it, for
sulphur particles when mixed with melted nitre
immediately ignite it. But the proof that the igneous
particles collected in the heated crucible are of a
nitro-saline nature is this, that any sulphureous matter
cast into the said crucible is ignited by those particles;
but sulphureous particles are not thrown into a state
of extremely rapid and fiery motion without the aid
of nitro-aerial particles.

We remark further that sulphureous particles are of
so crass a nature that we can scarcely imagine, however
heated they may be and however minutely divided,
that they will become so subtle and nimble as to be
able to penetrate, like fiery particles, metals, glass,
and such like very solid things, and this seems to be
confirmed by the following experiment. For let a
polished metal plate be kept for some time in the

20 Mayow

flame of a candle so that the igneous particles deeply
penetrating the said plate make it hot. But that the
igneous particles entering the plate are the nitro-
aerial particles of fire and not sulphureous is evi-
dent from this, that the sulphureous particles adhere
to the outer surface of the plate in the form of soot
and do not at all penetrate the plate. And yet we
cannot doubt but that the sulphureous particles adher-
ing to the plate were on fire, as far as their nature
allows. For it must be supposed that the sulphureous,
particles which ascend from the wick into the flame are
on fire from their first entrance into the flame, since
the flame could not be produced without the burning of
sulphureous particles. Nay, the black colour of these
particles indicates a burning of some sort. But this
will be made clearer by what will be said below.

Finally, the nitro-aerial particles in the flame pro-
duced by solar rays collected by a burning-glass are
particularly bright. This celestial flame appears to
be due merely to the nitro-aerial particles of the
atmosphere set in fiery motion by the action and
intense impulse of light. And this we must suppose
is the reason that antimony, when calcined by the
solar beams, is fixed and made diaphoretic, just as
if it were changed into Bezoardicum minerale by
spirit of nitre poured upon it and drawn off again
and again. Indeed, it is probable that it is the
nitro-aerial particles with which that spirit abounds,
and in some motion of which the solar rays consist^
that fix antimony and render it diaphoretic. It
favours this view that antimony acquires a diaphoretic
virtue, not only from the spirit of nitre and the solar
rays, but also from the flame of nitre in which nitro-
aerial particles are more densely collected. Nor
should it be overlooked that antimony, calcined by

On Sal Nitrum ana JVitro- Aerial Spirit 21

the solar rays, is considerably increased in weight,
as has been ascertained by experiment. Indeed, we
can scarcely imagine any other source for this increase
of the antimony than the nitro-aerial and igneous
particles fixed in it during calcination.

I am aware that it is the common opinion that
the diaphoretic virtue of antimony is due to the
loss of its extraneous and combustible sulphur in its
calcination. But I am not sure that this view is
quite consistent with truth. For it is well known
that if antimony and nitre are mixed and thrown
into a heated crucible, a very impetuous flame will
arise from them, since the sulphur of the antimony
ignites the nitre mixed with it. If, however, the
antimony has detonated (as the chemists phrase
it) with about a double quantity of nitre, then
nitre mixed with it will no longer produce a flame,
since the combustible sulphur of the antimony has
been entirely removed in the first detonation. And
still the antimony has not yet acquired the diapho-
retic virtue. Hence, for its further fixation, charcoal
or some sulphureous matter should be put from time
to time into the crucible in which the antimony,
along with the nitre last added to it, has been fused,
so that the nitre may ignite and the antimony be
fixed by its long-enduring flame. Clearly, then, the
fixation of antimony appears to be caused, not so
much by the removal of its extraneous sulphur, as
by the fixation in it of the nitro-aerial particles in
which the flame of nitre abounds.

The reason why an addition of tartar to nitre
contributes greatly to the fixation of antimony is
obvious from what has been said. For I think it
must be attributed to the tartar being imbued with
such sulphur as is suitable for gradually and thoroughly

22 Mayow

burning the nitre. For tartar mixed with nitre effects
its calcination in the best way, as has been shown
above. And hence it is that antimony kept in the
flame of nitre, kindled by the sulphur of tartar and
long burning, is fixed by the nitro-aerial particles of
the nitre and becomes diaphoretic. Nor is it probable
that salt of tartar contributes anything to the fixation
of antimony. For a fixed salt such as that of tartar
is quite unsuitable for exalting the emetic property
of antimony. Otherwise salt of tartar, but not tartar
itself, would have to be used for the calcination of
antimony. We remark, lastly, with respect to the
fixation of antimony, that it appears advisable to
begin its calcination in the first instance with nitre
alone, so that the nitre may kindle and remove the
impure sulphur of the antimony, and then to mix
tartar with the nitre, that the remainder of the
nitre, now that the sulphur of the antimony has
been removed, may be burned by the sulphur of the
tartar, and the fixation of the antimony completed.

By this hypothesis of ours, it is not difficult to
explain why fires that burn with a bright flame
purify the air from pestilential miasma, and are
consequently so beneficial in contagious diseases.
For no doubt the nitro-aerial particles which are
inhaled by animals in respiration (as will be shown
below) approach from all sides for the production
of the flame, and are hurried along in it with a
motion of the greatest velocity. And the result is
that these particles are purged by the motion and
the fire from their poisonous taint. But the subject
of fire will be treated more fully in Chapter VII.

On Sal Nitrum and Nitro-Aerial Spirit 23

CHAPTER IV

OF THE SOURCE OF ACID LIQUIDS; ALSO OF THE
TERRESTRIAL PART OF THE SPIRIT OF NITRE

That the spirit of nitre is a compound, and that it
is derived partly from the air and partly from the
earth, has been shown above. We have already
treated of its aerial part ; so that its terrestrial and
acid part remains for discussion.

It is extremely difficult to understand how the
spirit of nitre originates in the earth. For earth
appears to possess the nature of a fixed, rather than
of an acid, salt. And yet it is undoubtedly true
that if exposed to the air it will, after some lapse
of time, be impregnated with nitre. But it* has
been shown above that the acid salt of which the
nitre in part consists originates in the earth. But
that it may be understood how the acid spirit of nitre
is generated in the earth, let me be allowed to pre-
fix some observations regarding the spirit of sulphur
and other acid liquids, because there exists among
all acid spirits a very great likeness and affinity.

Hitherto the opinion has prevailed that an acid
salt of a vitriolic nature lies concealed in the struc-
ture of sulphur, and that from this, exhaling in the
deflagration of sulphur and collected in a superim-
posed glass bell-jar, the acid spirit of sulphur is
composed. But it seems scarcely probable that a
spirit so corrosive should reside in common sulphur,
which has a sweetish and by no means acid
taste. Nay, sulphur seems to have rather the

24 Mayow

nature of an alkaline than of an acid salt, as is
proved by the fact that common sulphur will enter
very readily into combination with the fixed salts
allied to it. For it must not be said here, that th^e
combination of fixed salts with sulphur arises from
the secret presence of an acid salt in the sulphur
with which the fixed salts seek a union. For if
such were the case, effervescence and heat would
be produced by the union of the sulphur and the
fixed salt, as happens in an encounter between
opposite salts. Moreover, when contending salts
are mixed together, they destroy each other and
are changed into a tertmm quid which is altogether
different from what existed before. But, in fact,
fixed salt and sulphur ^f melted at a low temperature
unite without any effervescence whatever ; and neither
of them is destroyed. On the contrary, their powers
are mutually increased, as if they had united in a
friendly league.

Wherefore since it is improbable that so acid a spirit
is contained in the mass of sulphur and is not elicited
unless the sulphur is burned, why should we not sup-
pose that the spirit is produced, by the burning of
the sulphur, in the following way ? For I suppose
that common sulphur contains in addition to its sul-
phureous particles pure and simple, a salt of a fixed
or rather metallic nature in the closest union with its
sulphureous particles, which saline part sometimes
crystallises when sulphur is dissolved by the spirit of
turpentine.

Further, it should be noted that the flame of kindled
sulphur, as indeed flame of every kind, consists in this
that the sulphureous particles of the deflagrating
substance and the nitro-aerial particles mutually
excite themselves to a very rapid motion, as we have

On Sal JVitrum and Nitro- Aerial Spirit 25

shown above. But as the minutely divided saHne
particles of the sulphur are very closely united to its
sulphureous particles, it happens in the deflagration
of sulphur (when the sulphureous and nitro-aerial
particles throw each other into fiery motion) that the
saline particles of the sulphur, adhering to its sul-
phureous particles, are by frequent impacts of the
nitro-aerial particles struck, rubbed, and comminuted,
so that the saline particles from being often rubbed
and pounded, are at last sharpened like small swords
and are moreover so attenuated as to be changed from
rigid and solid into flexible and fluid particles. The
saline particles of the sulphur in fact which were
previously of a fixed nature change, after they are
thus sharpened and made fluid, into an acrid and acid
liquid, and probably constitute the common spirit of
sulphur.

That the facts of the case are as stated may be
inferred from a careful study of the flame of sulphur
since it is very different from other flames. For
nitro-aerial particles do not shine ruddily and glow
in the flame of burning sulphur as in other cases, but
owing to their diminished motion appear blue, so that
it would appear that some third substance is interposed
between the nitro-aerial and sulphureous particles,
and that by it these fiery particles are hindered in
their motion. For as the nitro-aerial and fiery
particles, when in violent agitation, glow, so when
their motion is retarded they appear of a blue colour.
And this is the reason that the flame of an expiring
lamp is wont to be blue. But of this more else-
where.

It serves to confirm what has been said that the
flame of sulphur in consequence of the somewhat
sluggish movement of the fiery particles is less caustic

26 Mayow

and almost harmless. For if a finger or anything
combustible is thrust into the blue flame of sulphur,
but not into the sulphur mass, it will not be burned
as by other fires, but will remain for some time
uninjured. To this we add further that the flame
of sulphur does not expand like other flames but
bursts forth from time to time and seems as it were
to eff'ervesce. From this it is to be inferred that
there is a third substance mixed with it on which the
fiery particles act. And that these particles, of a saline
or metallic nature, mixed with the flame of the sulphur
and sharpened by the rubbing of the nitro-aerial
particles and brought at last to a fluid state, constitute
the acid and corrosive spirit of sulphur, we take to be
at least a probable conjecture; for otherwise I have no
notion how the acid spirit is produced, for it is improb-
able that it exists in the structure of the sulphur
before its combustion, as has been shown above.

To this we further add that the oil of vitriol expelled
after several days' distillation seems to be produced
in nearly the same way. For it is certain from
experience that if the distillation of vitriol is con-
tinued with the strongest fire for ten or even more
days, acid spirit will still all the while pass into the
receiver. But it is scarcely to be believed that any
acid spirit is so fixed and ponderous as to be able to
remain so long in the hottest fire. We must rather
suppose that nitro-aerial particles of the fire, in the
course of the long continued distillation of the vitriol,
encounter the metallic sulphur of the colcothar and
effervesce — the result being that the saline particles
of that sulphur which are placed among the mutually
rubbing fiery particles are pounded and comminuted
so as at last to be sharpened and brought into a fluid
state. And these at last carried up by the force of

On Sal Nttrum and JSfitro- Aerial Spirit 27

the fire compose the oil of vitriol very much in the
same way as we showed above that the spirit of
sulphur is produced when sulphur is burned. And
indeed it is probable that the distillation of vitriol
will go on as long as any of the saline particles of the
colcothar remain, these being brought into the fluid
state under the action of heat in the manner afore-
said.

Further, I do not know but that acid spirits distilled
from heavy woods, such as Guaiacum wood and the
like, are formed in a similar way by the action of fire
during distillation. Indeed, Guaiacum wood before
distillation does not seem to be endowed with an acid
but rather with a fixed salt. For its powder or decoc-
tion effervesces when spirit of vitriol (but not when
fixed salt) is poured on it. It corroborates this view
that the saline particles of that wood are in close
combination with the sulphureous particles, as will
be shown below, whence it is that the nitro-aerial
particles of the fire, encountering the sulphureous
particles of the wood in the course of distillation, rub
the saline particles and bring them into a fluid state
in the manner aforesaid. We observe also in passing
that acid spirits distilled from sugar and honey appear
to be produced in a not very dissimilar way by the
action of the nitro-aerial spirit of fire. For such
plants as have no acid taste and yet jdeld an acid
spirit on distillation are composed of sulphureous in
intimate union with saline particles, and are therefore
suited for yielding an acid liquid in the manner
aforesaid.

As the nitro-aerial spirit of fire, encountering saline-
sulphureous particles with very brisk motion and
fiery effervescence, rubs down in a moment and
reduces to a fluid state the saline particles which are

28 Mayow

closely involved with the sulphureous, so the same
nitro-aerial spirit effervescing in a slower motion
with saline-sulphureous particles, changes the saline
particles into an acid liquor only after some time has
elapsed. And an example of this is to be sought in
vitriol when calcined to the entire removal of the
acid spirit. For if that vitriol has been exposed for
some time to moist air it will be impregnated anew
with acid spirit. Indeed, nitro-aerial spirit encounters
the metallic sulphur of colcothar in a gentle manner
and effervesces with it in an obscure way, whence it
is that the saline or metallic particles of the sulphur
are brought in the manner aforesaid to a state of
fluidity. Certainly we can scarcely imagine any
other mode for the formation of the vitriolic spirit
in colcothar, for it does not arise in the colcothar
immediately after distillation, and we cannot suppose
(as has been elsewhere shown) that it is entirely de-
rived from the air.

Further, the acid spirit of which vitriols are
composed seems obviously to be produced in the same
way. For vitriols are produced from the stone or
rather the saline-sulphureous earth usually called
Marchasite, and from it on the application of fire
the flowers of common sulphur are elicited in con-
siderable abundance. But after this earth has been
exposed for some time to the air and wet weather and
then (as its nature is) has fermented spontaneously, it
will be found to be richly impregnated with vitriol.
No doubt the nitro-aerial spirit, effervescing with the
metallic sulphur of these Marchasites, converts their
more fixed part into an acid liquid which, directly it
is produced, attacks the metallic particles of the said
stone and draws them out and at last coalesces with
them to form vitriol.

On Sal Nitrum and Nitro- Aerial Spirit 29

But indeed iron rust also, which has a vitriolic
nature, seems to be produced by the action of
nitro-aerial particles meeting with the metallic
sulphur of iron, for the saline particles of the
iron when brought into a fluid condition in the
manner aforesaid corrode and dissolve its metallic
particles ; and from these combined, rust or a sort
of imperfect vitriol is produced — very much as if
the iron had been smeared with some acid liquid.

It should also be noticed that acid salt or sourness
is produced by the action of nitro-aerial spirit not
only in solids but also in liquids. For it is not
enough to say that the acidification or the fluidity
of the salts arises from this, that saline particles which
before had been mutually hidden by the intervention
of the other particles, afterwards, the bond of the
mixture being loosed, flow together and spread
themselves out through the whole structure of the
substance, and that when these gain dominion
sourness is produced in the mixture as some have
imagined. For we must suppose that all the salts
of the liquid were even from the first diffused
through its whole mass, since they were dissolved in
the liquid. It should rather be maintained that
the souring of liquids is caused by the change of
their fixed salt into an acid salt, a result which
is probably due to the action of nitro-aerial spirit.
For liquids abounding in fixed salt and sulphur, such
as French wine and strong ale, acquire acidity
from lengthy fermentation. Moreover, the fermenta-
tion of the liquids consists in the effervescence of
nitro-aerial particles, whether contained in the liquid
or entering from without, with the saline-sulphureous
particles of the liquid, as I shall endeavour to show
below. And hence it is that the saline particles of

30 Mayow

the liquid closely combined with the sulphureous
particles are beaten and rubbed by the nitro-
aerial particles and at last liquefied in the manner
aforesaid. It corroborates this view that wines or
strong ale long exposed to the solar rays or kept in
a warm place turn in the course of time into vinegar.
In fact the nitro-aerial particles communicated to
these liquids by the solar rays or by fire (for I
intend to show in another place that every kind of
heat is due to nitro-aerial particles put in motion)
effervesce with the saline-sulphureous particles of
these liquids, with the result that the saline particles
are sharpened by the action of the nitro-aerial
particles and converted into acid salts. And what-
ever in fine aids the fermentation of liquids and
throws their particles into violent commotion, as,
for example, very warm weather and thunder, accel-
erates the souring of the liquids. To this I add that
if common sulphur is dissolved in water in which
quicklime has been slaked, or in lye, this solution
which was imbued at first with fixed salt will in
course of time become acid, so that the sulphur
will not any longer remain dissolved in it.

It is also to be noted that saline and sulphureous
particles exist in a fluid state in liquids — the conse-
quence being that the saline particles in liquids
cannot be so rubbed and comminuted by the action
of nitro-aerial particles as in the case of solids. And
this seems to be the reason why the acid salt of
soured liquids is less sharp and corrosive than the
spirit of sulphur and other eminently corrosive liquids
of the same kind.

In the light of what has been said it will not
be difficult to understand how the acid spirit of nitre
is generated in the earth. For it was pointed out

On Sal Nitvum and Nitro- Aerial Spirit 31

in another place that fertile earth is nothing but
sulphur and fixed salt both immature, in a state of
the closest combination, and indeed a dark purple
clod of earth appears not very unlike colcothar, except
that in the latter sulphur is combined with a metallic
salt but in the former with fixed salt. As then the
nitro-aerial spirit effervescing in a fiery motion with
the particles of common sulphur, or again encounter-
ing with more gentle heat the saUne-sulphureous
particles of colcothar, sharpens more quickly or more
slowly their saline-metallic particles and brings them
to a fluid condition ; so also the same nitro-aerial spirit,
descending in virtue of its most penetrating nature
into the depths of the earth, there attacks the ter-
restrial sulphur and fermenting with it in an obscure
motion rubs, attenuates, and sharpens the saline
particles which are firmly clasped in its bosom, so
that they at last became flexile, liquid^ and in the
highest degree acrid. The saline particles of the
earth when made fluid in this manner become a
suitable abode in which nitro-aerial particles may be
hidden and detained. And in my opinion the spirit
of nitre, of the sort obtained by distillation, is com-
posed of these two firmly united.

And so at last I have endeavoured to show that
all acid salts are produced from saline particles
brought to a state of fluidity or fusion by means of
nitro-aerial spirit, and also how this is done. With
respect to the difference of acid liquids — this must be
supposed to result from diversity of the salts out of
which they are formed, as also from this, that
the fixed salts are rubbed and sharpened now in
a greater and now in a less degree by the nitro-
aerial spirit. And yet there is a great aflSnity and
likeness among all acid salts, and in them all, as in

32 Mayow

an appropriate medium, nitro-aerial and igneous
particles reside, as will be shown below.

The particles of nitrous spirit generated in the earth
in the manner aforesaid, as soon as they are produced,
approach the seeds of the fixed salts which, as has
been elsewhere shown, are hidden in the bosom of the
earth, and solicit and call them forth into conjugal
union as a suitable consort and of their own kin ;
and, lastly, from them, combined in the closest alliance,
sal nitnim is produced, much as in colcothar or
vitriolic earth, other saline particles that have been
brought to a fluid condition by nitro-aerial spirit,
meeting other saline particles of a nature akin to
their own, coalesce to form vitriol as we have indicated
above.

It follows from what has been said that there is no
such great repugnance between fixed and acid salts
as is commonly supposed. That they indeed boil up,
when mixed together, with remarkable violence should
not be imputed to any enmity between them but
rather to a sort of conjugal affection. These salts, in
fact, grind each other in order that they, being divided
to the utmost extent possible, may be united in a
closer bond.

From what has been said the reason is clear why
nitrous but not purely saline salts are extracted by
lixiviation from the earth, for particles of nitrous
spirit generated in the earth take into union with
them and render nitrous all the fixed salt which has
attained to perfect maturity. And, indeed, it is prob-
able that the seeds of the fixed salts existing in the
bosom of the earth cannot be lixiviated and extracted
without the aid of nitrous spirit.

That nitre is generated in the earth in the manner
aforesaid may be inferred also from the fact that it is

On Sal JSJitnim and Nitro-A'erial Spirit 33

principally produced in such soil as is imbued with
saline - sulphureous particles — as, for instance, in
slaughter-houses, stalls, stables, and the like. In fact,
fixed or volatile salts provide suitable material for the
production of nitre, but sulphureous particles con-
tribute in no other way to the generation of nitre
than by exciting, when they effervesce with nitro-
aerial particles, that heat in the earth's bosom by
which first nitrous spirit is produced and then nitre
itself. For, as has been shown above, the sul-
phureous particles of terrestrial matter must not be
supposed to constitute nitre in part.

It is in some measure established I think from what
has been said what the elements are of which sal
nitrum is composed. For it seems to consist of salt
of three kinds, of which one, the most active, is derived
from the air, and it has an ethereal and fiery nature.
This salt, as an architect, forges for itself from terres-
trial matter a saline vehicle in which, as in a fitting
subject, it resides. The saline vehicle along with the
fiery salt which occupies it forms the spirit of nitre,
which from the moment of its production meets the
fixed salts of the earth which have attained to proper
maturity, and coalesces with them to form common
nitre. So much then for sal nitrum.

34 Mayow

CHAPTER V

OF FERMENTATION

Of Nitro- Aerial Spirit^ so far as fermentations leading to the birth
or death of things are caused by it.

When nitro-aerial spirit effervesces with the saHne-
sulphureous particles of the earth in the manner
described in the previous chapter, then the nitrous
spirit produced by its action meets the fixed salts of
the earth, and there is kindled in the earth's bosom that
mild and enduring warmth by which the common
mother fosters and quickens the seeds hidden in her
womb. But that this fermentation may be more
clearly understood, let me first speak shortly of the
fermentative principles of things.

Among the elements of natural things nitro-aerial
spirit holds the first place, so that it may rightly be
called Mercury, since it is a substance exceedingly
subtle, agile, and ethereal, and is also the primar}^
instrument of life and motion not only in plants but
also in animals, as I shall try to show below. Among
the elements of the Peripatetics the two chief are Fire
and Air, but for these two our nitro-aerial mercury
might justly be substituted, since it possesses a really
fiery nature and constitutes also the most active and
fermentative part of the air, as will afterwards be
shown. With regard to the spirit of the chemists,
which usually leads their band of elements, I am quite
unable to understand what they mean by the very
grand word spirit. For with respect to the spirits of
fermented liquids — that is, those which blaze when

On Sal Nitriim and Nitro- Aerial Spirit 35

thrown into the fire — they are to be referred to the
second element of the chemists, to wit, sulphur. But
corrosive and saline spirits which alone remain ought
to be entered in the register of the salts. So that
clearly nitro-aerial particles should alone be dis-
tinguished by the name of spirit. Nitro-aerial spirit
appears in very different conditions according as it
is at rest or in motion, and that slower or very nimble,
as will be shown more fully below.

Tn the list of elements sulphur has a claim to the
next place because after nitro-aerial mercury it is
the most fermentative. And indeed, except these
two, there do not seem to be any active elements.
Sulphur is seen in various states for now it lies inert
and lulled to sleep, now it is raised to proper vigour
and maturity ; sometimes indeed it is extremely fierce
and irrepressible, as will be shown below.

Nitro-aerial spirit and sulphur are engaged in
perpetual hostilities with each other, and indeed from
their mutual struggle when they meet and from their
diverse state when they succumb by turns all the
changes of things seem to arise.

Salt, which has a passive nature, should be reckoned
as the third of the elements. For in whatever way
it may be volatilised there never, I think, begins in
it a dance of internal movements. Salt is either fixed
or volatile, both are however of nearly the same
nature : but there is a greater variation in the con-
dition of salt when it is changed from purely saline
into acid. Salt has great affinity and relationship with
nitro-aerial spirit and also with sulphur ; for these
very active elements are by turns married to salt as
to a fitting bride, and are fixed in its embrace, as will
presently be shown.

Besides the elements already mentioned, water and

36 Mayow

terra damnata are to be found in almost every thing.
Water seems to be a suitable vehicle for nitro-aerial
spirit and sulphur, and together with terra damnata
contributes to the building up of the frame of things
in due strength and consistency.

Thus far of the elements viewed in themselves ; we
have next to consider them in regard to how far they
act on each other and mutually enter into various
combinations. Hence proceed the internal move-
ments of things and their rise and destruction.

First then, in the birth of plants, the nitro-aerial
spirit or Mercury when set in motion by the impulse
of solar rays descends in virtue of its very penetrating
nature into the depths of the earth and attacks there
its most bitter en^my terrestrial sulphur, firmly
united with fixed salt and nearly hidden and buried
in its embrace ; and by its very frequent vibrations
lashes and wears it. The sulphur thus aroused and
to some extent liberated from its terrestrial yoke by
the frequent blows of the nitro-aerial particles begins
a contest with its nitro-aerial foe, and from their
mutual disturbance a rather notable effervescence is
excited in the bosom of the earth, as we have indi-
cated above. Meanwhile the particles of fixed salt
held in the embrace of the sulphur are so worn by
numerous strokes of the nitro-aerial spirit that they
are brought at last into a fluid condition in the way
described above. And by these, when liquefied, any
fixed salt still adhering to the terrestrial sulphur is
lixiviated (as was shown above). And so at last the
nitro-aerial Mercury, having according to his furtive
nature secretly entered the territory of his enemy
sulphur and robbed him of his saline consort, wedded
to her as to a suitable spouse succumbs, fixed by fate
of an unhappy marriage, and almost buried in her

I

On Sal Nitrum and Nitro- Aerial Spirit 37

embrace. For it has been shown above that nitro-
aerial spirit is detained as in a suitable hospice in
fixed salt which has passed into the fluid state. But
when held in the embrace of a salt and coalescing
with it, which is partly acid partly saline, to form
nitre, it exists in a condition of the greatest fixity.

But meanwhile the terrestrial sulphur which, not
so long ago, wrapped in wedlock with fixed salt, was
fixed indeed, now, the saline yoke thrown off by help
of the nitro-aerial spirit, attains a condition of vola-
tility and gets the mastery, the nitro-aerial spirit
being depressed. And in this way, in fine, extremely
volatile and inflammable sulphureous particles (such
as the oils which are obtained by distillation from
plants) are very likely produced from the rude mass
of the earth, which seems to behave like a caput
mortuum. For the volatilisation of sulphur consists
in its being liberated from a union with fixed salt.
And it is therefore clear that the fixation of sulphur
arises from its intimate union with a fixed salt. For
if sulphureous oils are combined with fixed salt, as is
the case in soap, they lose their inflammability alto-
gether. For soap, which is partly composed of oil,
will not blaze if thrown into the fire.

When in this way nitro-aerial spirit, effervescing
obscurely with terrestrial matter, raises its sulphureous
part to the requisite volatility and coalesces also with
its saline part to form nitre, the elements of natural
things are brought into the condition required for
the production of plants. For all plants seem to be
composed of terrestrial sulphur in a sufficiently volatile
and inflammable condition, and of nitro-aerial spirit
held in the embrace of salt and subdued, that is to say
of nitrous salt, as will be shown presently.

It serves as a proof of the origin of vegetables in

38 Mayow

this way that at the time when vegetables chiefly
spring from the earth, the nitro-aerial spirit ferments
most actively with terrestrial matter, and sal nitrunt
is chiefly produced in the earth : in fact experience
shows that nitre (which we suppose to be formed by
nitro-aerial spirit effervescing with the saline-sulphu-
reous particles of the earth) is produced in the earth
in greater abundance in the beginning of spring than
in the other seasons of the year. In winter, indeed,
nitro-aerial particles and terrestrial sulphur are com-
pressed by frost and are fettered as it were and
hindered almost from moving at all. But at the be-
ginning of spring nitro-aerial spirit is set in motion by
the greater heat of the sun, and the structure of the
earth is laid open now that the ice has melted. And
then the nitro-aerial spirit set in motion descends deep
into the earth, and meeting there with its saline-sul-
phureous particles, minutely broken, gives rise to an
intense enough effervescence, with the result that
nitre is generated in abundance, and plants grow up
luxuriantly.

From what has been said we can see why animal
excreta, salts of lye and also quicklime, and similar
substances imbued with fixed salts fertihse the soil.
Indeed the saline-sulphureous excreta of animals, as
also fixed salts in union with terrestrial sulphur, are
specially adapted for effervescing with nitro-aerial
spirit, and they also supply appropriate material for
the production of nitre and consequently contribute
not a little to the production of plants.

Thus then the so much talked of fermentation by
which the numerous family of plants is produced from
the bosom of the earth, appears to be nothing else
but the internal motion of nitro-aerial particles when
they meet with the sulphur and salt of the earth, in

On Sal Nitruin and Nitro-A'erial Spirit 39

virtue of which terrestrial nitre is produced and the
sulphur brought to a suitable volatility.

It follows from what has been said that the salts of
which plants are composed are to some extent nitrous
and not purely saline, as we intimated above. For all
vegetable salts are derived either from the air or from
the earth. As regards the air it is by no means to be
supposed that an alkaline and fixed salt resides in it ;
nor is the earth impregnated with a purely saline salt,
for only nitrous salts can be extracted from it by lixi-
viation. And hence we may conclude that the salts
of plants are nitrous and not purely saline. Hence
in soil on which plants grow abundantly no nitrous
salt is to be found, the reason being that all the nitre
of the soil is sucked out by the plants. But when
plants are calcined to ashes, the acid spirit of the
nitre of which they are composed goes off as vapours,
while the other element of the nitre — to wit, the
alkaline salt — is left in the ashes. And hence it is
that plants yield a greater quantity of fixed salt
when burned fresh and with the least possible flame ;
but this does not result as some suppose because the
alkaline salt goes off as vapours when the plants
are slightly dried, for it has an exceedingly fixed
nature and remains undiminished and intact in the
hottest fire. But when plants containing much sul-
phur are dried and then burned in a bright flame,
the sulphureous parts, burning with a fiercer flame^
kindle the nitrous salt, and carry the whole of it
away with them as vapours, very much as when
gunpowder is ignited. If, however, green herbs are
calcined with the flame kept down, their volatile
sulphur, together with the original moisture, passes
into smoke and goes away, while the nitrous salt
remains behind ; but if calcined in a hotter fire, the

40 Mayow

spirit of nitre is expelled as by distillation, the alkaline
salt being left with the terra damnata in the ashes ;
and in proportion to the violence with which the
calcination is effected, in that proportion are the salts
alkalised when the nitrous spirit is expelled. Hence
we may gather that it is not advisable violently to
calcine diuretic salts (so named from promoting
urine), for, by doing so, those salts are deprived of
their nitrous and diuretic spirit. And hence it is
that the lye, say of the ashes of Genista^ is more
efficacious in dropsy than its fixed salt thoroughly
alkalised by violent calcination.

The nitrous spirit of plants seems to be clearly
present in a fire of burning charcoal, for the smoke
from that fire assails the nostrils when brought near
to it, very much in th^ same way as the vapour that
proceeds from the spirit of nitre. And indeed it is
likely that the nitrous spirit which exhales from
burning charcoal in the form of smoke, is the reason
for that smoke being so acrid, and for its sometimes
causing suffocation.

And further the nitrous spirit of plants manifests
itself strikingly in their fermenting juices, when these
have been kept for some time in a glass vessel care-
fully closed. For when these liquids are drunk the
nitrous particles irritate the nervous parts of the
throat with a quite striking pungency and bring on
an almost convulsive choking. So that, when liquids
of this sort are drunk, they are commonly and not
improperly said to cut. Moreover, the nitrous par-
ticles in which these liquids abound seem to be the
cause of their being so cold. For nitre mixed with
liquids makes them very cold, and almost freezes
them, as will be shown more fully elsewhere.

In some plants the oily parts are so heavy and so

On Sal Nitviim. and Nitro- Aerial Spirit 41

closely united with nitrous salt that they are not
separated from each other by calcination ; but the
burning sulphureous particles carry the nitrous par-
ticles away with them as vapours. And hence it is
that plants of this sort yield only a small quantity
of fixed salt, as is the case with resinous woods, such
as Lignum sanctum and the like.

Nor should it be overlooked that the nitre innate
in plants contributes not a little to their burning, and
that those which abound the most in nitrous par-
ticles take fire at once, even when they are green
and full of moisture. Among these the ash is espe-
cially remarkable, for be it ever so green it yet burns
with a bright flame. But, indeed, its richness in nitre
may be inferred from the fact that while burning
it gives out, from time to time, cracks like kindled
nitre.

Thus far, we have considered the fermentation
tending to the production of plants. We have still
to inquire shortly as to the internal motion by which
plants rush to their destruction.

In regard to this, it is our opinion that the fer-
mentation which tends to the destruction of plants is
also caused by the mutual agitation of the nitro-aerial
and saline-sulphureous particles — with this distinction,
however, that in the origin of vegetables, nitro-aerial
spirit, when put in vigorous movement, attacks sul-
phur existing in a fixed state, and when the sulphur
has been brought to volatility, the nitro-aerial spirit
is fixed, imprisoned in saline bonds, as has been shown
above. But, on the other hand, in the destruction
of things, the internal movement is for the most part
set up by the sulphur being too highly exalted. In
fact, the sulphureous particles in a state of too vigorous
movement attack the nitro-aerial spirit when lying

42 Mayow

asleep in the bosom of the fixed salt, and mindful
as it were of former wrongs, thrust it forth from its
saline shelter and set it in motion ; but the nitro-
aerial spirit, when violently torn from its saline
partner, throws everything into disorder by its im-
petuous motion and loosens the union of the com-
pound. But in order that what has been said may
be better understood, let us consider in how many
ways things rush to their destruction, for in all
these we shall find that internal movement is caused
by sulphureous particles and nitro-aerial spirit whether
the latter is derived from without or not.

In the first place, the mode in which the structure
of things is most speedily dissolved is Fire. But this
is nothing else than an exceedingly impetuous fer-
mentation of nitro-aerial and sulphureous particles in
mutual agitation, as has been shown above. Thus,
in combustion, sulphureous particles, moving with
extreme velocity, throw into a most violent and
fiery motion the nitro-aerial particles which exist
in a state of fixation. This is evident when nitre is
burned, for in its burning, nitro-aerial particles which
were previously fixed and inert in the embrace of
the fixed salt, are thrown into fiery motion by the
agency of the sulphureous particles. And indeed
it is probable that even the nitro-aerial particles of
the air are in a fixed state previous to their being
roused into fiery motion, as I shall endeavour to
show elsewhere.

As the destructive power of fire is due to nitro-
aerial particles, so also every internal movement
which things undergo seems to depend upon a
less violent agitation of the same particles. And
it is a proof of this that in putrefaction and in
nearly all fermentative movements some heat is

On Sal Nitnim and Nitro- Aerial Spirit 43

excited, and this must be supposed to result from
the motion of nitro-aerial particles, as will be shown
immediately. How great moreover is the resem-
blance and affinity between fire and all other fer-
mentations will appear from what follows.

With regard to fire, it is to be noted that for the
burning of things, it is necessary that nitro-aerial
particles should either be already in the burning
substance or be supplied from the air. Gunpowder
burns very readily on account of the nitro-aerial
particles it contains ; plants burn partly from the
nitro-aerial particles they contain, and partly from
such as come from the air ; but sulphureous matter,
pure and simple, can only be ignited by nitro-aerial
particles supplied by the air.

And, just as for the production of fire, so also for
exciting fermentations in plants, both sulphureous
and nitro-aerial particles must either exist in the
things to be fermented or be supplied from without.
The juice expressed from plants, such as the must
of wine or of apples and the like, effervesces on
account of the nitro-aerial and sulphureous particles
which it contains. For we have shown above that
nitrous salts and therefore also nitro-aerial particles
are contained in most plants, though, at the same
time, the nitro-aerial spirit supplied by the air con-
tributes much to the fermentation of these liquids,
for very warm weather intensifies the action in no
small degree. Further, that the fermentation of the
aforesaid liquids, as also of all things whatsoever, is
due to the mutual agitation of nitro-aerial and
saline-sulphureous particles, is evident from the fact
that liquids of this kind, and indeed nearly every
thing, become sour in fermenting ; for it has been
shown above that acidity is caused by the action of

44 Mayow

nitro-aerial spirit. Should any one be inclined to
think that the fermentation of the said liquids
ought not to be classed among effervescences with
a destructive tendency, I reply that although the
juices expressed from plants become more perfect
by fermentation so far as their use to man is con-
cerned, yet, in respect to the compound whose
structure it impairs, the aforesaid effervescence is
rightly called destructive.

But when the decay of things is caused by extran-
eous heat and moisture, the internal movement is
mainly effected by nitro-aerial particles supplied by
the air. For nitro-aerial particles abound in a moist
warmth ; for we must suppose that heat of all kinds
is due to their motion.^ When therefore nitro-aerial
particles enter any substance along with extraneous
moisture, they engage in conflict with the saline-
sulphureous particles which they meet, and in con-
sequence of their mutual agitation the structure of
the compound is dissolved. Hence such things as
exclude nitro-aerial spirit protect substances from
corruption. And this is the reason why vegetable
fruits, and even flesh, when covered with butter are
preserved for a long time from putrefying, also iron
smeared with oil is not corroded by rust. And
indeed oil and other things containing sulphur
appear to be extremely well adapted for excluding
nitro-aerial spirit. For sulphureous and nitro-aerial
particles, from their mutual enmity, keep off and
repel each other, as I have attempted to show in
another place ; and for a similar reason, spices which
are full of sulphur keep dead bodies for a long time
from putrefying.

It is an additional proof of the foregoing that
those things which consist of a combination of

On Sal Nitriim aud Nitro-A'erial Spirit 45

sulphur and salt, fixed or volatile, are particularly
adapted for producing fermentation. Of this kind
are yolk of egg and all sorts of gall of animals, as
also soap — all of which when mixed with any farina-
ceous mass make it swell and ferment in cooking.
But the fermentative nature of the things named
seems to be due to this, that in cooking, the nitro-aerial
particles of the fire meet their saline-sulphureous par-
ticles and effervesce with them.

I add further, that the glow or warmth which
arises in nearly everything when fermenting, appears
to be caused by nitro-aerial spirit, as has been already
indicated. For I think it is clear, from what has been
said elsewhere, that a most intense and fiery heat
proceeds from nitro-aerial particles when thrown into
very rapid motion. And indeed we must suppose
that heat of every kind depends upon the same
particles when briskly agitated, for heat and fire
must be supposed to result from the agitation with
different degrees of motion of the same kind of
particles. For in glowing substances of all sorts the
presence of nitro-aerial particles is shown by suffi-
ciently clear signs.

As to the heat resulting from fire and from the
fermentation of things, it has now been shown that
it is caused by the motion of nitro-aerial particles.
As to the heat of antagonistic salts when mixed
together, we must imagine that it too is caused by
nitro-aerial spirit. For it has already been shown
that acid and corrosive liquids are produced by the
action of nitro-aerial particles, and that nitro-aerial
spirit resides in them as in a fitting subject ; although
I shall endeavour to show below that the heat pro-
duced by the fermentation of contrary salts depends
also upon nitro-aerial particles supplied by the air.

46 Mayow

Further, with respect to the heat which arises in
solid bodies when rubbed together, it is probably
due to nitro-aerial particles residing in those bodies
and thrown into motion by vehement rubbing ; for
the more solid kinds of wood appear to be rich in
nitrous particles as has been shown above. Nay,
that solidity and even rigidity are caused by nitro-
aerial particles I shall endeavour to show below.
Lastly, with respect to blood, and quicklime, and
other things of the same kind, it will be established
below that their heat is produced by nitro-aerial
spirit.

Lastly, we remark with regard to fermentation in
general that nitro-aerial spirit will not ferment with
sulphur unless the sulphur is to some extent fixed.
For liquids which contain sulphureous particles
highly exalted, such as spirit of wine, never effer-
vesce even though exposed to the warmest air, while
juice expressed from grapes and new ale (in which
the sulphureous particles have not yet attained to
vigour and inflammabiHty) ferment of themselves.
And indeed it is the saHne particles in union with
the sulphureous which seem to be the cause of
everything becoming acid in fermentation as we
have indicated above. For the saline particles which
were previously wrapped up in the sulphureous
particles, are afterwards by fermentation set free
from their fellowship, and besides brought into a
fluid condition as described above.

But although nitro-aerial spirit does not attack
highly exalted sulphureous particles, yet sulphureous
particles, when in the greatest vigour and agitation,
attack nitro-aerial spirit and throw it into a very
swift and fiery motion. For, as it is necessary that
sulphur should be to some extent in a state of fixation

On Sal Nitrum and Nitro-Aerial Spirit 47

in order to produce in substances the more sluggish
movement of fermentation, so, on the other hand,
for an effervescence exceedingly intense and igneous,
it appears to be necessary that nitro-aerial spirit
should exist in a somewhat fixed condition, but the
sulphureous particles in a state of vigour and
motion, as we have indicated above.

CHAPTER VI

OF NITRO-AERIAL SPIRIT IN SO FAR AS IT PRO-
DUCES RIGIDITY IN BODIES, AND THE POWER
OF RESILIENCE. ALSO OF THE CAUSE OF ELAS-
TICITY. INCIDENTALLY OF THE BREAKING OF
GLASS DROPS

Thus far we have treated of nitro-aerial spirit in its
state of motion and vigour ; it remains to contemplate
it in a state of rest. As the nitro-aerial particles in
a state of motion are the cause of nearly all natural
movements — so, on the other hand, they are the
cause, I think, of rigidity and the power of resil-
ience, when quiescent and securely fixed in the pores
of bodies.

For in order that glass or iron and the like may
become rigid and acquire the power of resilience
they must be made to glow in a very hot fire, and
then be quickly cooled by being plunged at once
into cold water, that so the nitro-aerial particles
conveyed by the fire to the said substances may
be obstructed in their movement by encountering
cold, and secured more firmly in the structure of
these substances. For the same nitro-aerial par-

48 Mayow

tides which, when whirled round and hot, separated
from each other the particles of these glowing sub-
stances and opened up their structure, now, when they
cease to move in consequence of encountering cold,
are fixed like wedges or very solid spikelets in their
pores. Things are hardened by them when fixed in
this manner, and indeed cold seems to close the pores
of things in this way only.

But that nitro-aerial particles reside in iron made
rigid in this way, is evident from the fact, that this iron
acquires the property of giving out fire when struck
by a flint. For we must suppose that the sparks
struck out from steel are caused by igneo-nitrous
particles of the steel bursting forth with extreme
velocity on account of the violence of the blow.
Indeed we perceive that the fire of these sparks is
very like burning nitre, and that they burn very
readily though struck out from the steel in a place
where there is no air — which is certainly a clear
proof that there are nitro-aerial particles in steel. So
that to strike fire from it there is no need — as in
other cases where fire is produced — for nitro-aerial
particles to be supplied from the air. It corrobo-
rates this view that if heated iron cools slowly, the
igneo-nitrous particles gradually extricate themselves
and escape through the open pores of the iron (for these
are not, as in the previous case, contracted by the cold) ;
so that the iron, from want of igneo-nitrous par-
ticles, becomes less rigid, and unfit to give out fire
when struck. And what the ingenious Dr R. Hooke
has set down in his Micrographia is not opposed
to this — to wit, that the sparks of steel, after their
extinction, are nothing but small globules or minute
vitrified bits of steel. For it must not on that account
be thought that little morsels of metal take the form

I

On Sal Nitriim and Nitro-Aerial Spirit 49

of flame when greatly agitated by a very violent blow,
but rather that the igneo-aerial particles hidden in
the pores of the iron are excited by the violence of the
blow into a really fiery motion, and that a little bit of
the iron is melted by them and changed into a sort of
glass.

As the rigidity of iron and glass and similar sub-
stances arises from nitro-aerial particles imparted to
them by fire, so probably the rigidity of frozen water
is also caused by nitro-aerial particles which, from
being fixed like pegs between the aqueous particles,
arrest their fluid movement and press them together.
For as in fire nitro-aerial particles whirled round with
swiftest motion disturb the particles of the substances
in which they exist and break them into minute parts,
so on the contrary in the cold, they, set up as
spikes, fasten like wedges among the particles of bodies
and cause them to become rigid, as has been said
above.

That nitro-aerial and igneous particles in a state of
rest produce rigidity and cold may be inferred from
the case of nitre itself in which the nitro-aerial particles
become extremely cold, and when mixed with vinous
liquids almost freeze them, and yet if they are agitated
by sulphureous particles they become in fact fiery, as
happens in the ignition of nitre. And hence it is that
if the hand or other member when stiff with cold be
brought near the fire it is hurt as if by fire and
even destroyed, for the nitro-aerial particles which
freeze as it were the chilly part in which they are fixed,
assume also a fiery nature when agitated by the heat
of the fire and burn it. So that without doing violence
to language cold may properly be said to burn.

In the foregoing we must seek for the reason why
water that has been boiled freezes sooner, as some

D

50 Mayoiv

suppose, on being exposed to cold. For nitro-aerial
particles derived from the fire abound in boiling water,
and these when they cease to move on exposure to
cold no longer agitate the aqueous particles but fix
and freeze them. For the case here does not seem to
be very different from that of glowing iron being
plunged into cold water, for the iron, cooling rapidly,
becomes more rigid and so to say firmly frozen. And
indeed in my opinion frozen water differs from
hardened iron chiefly in this, that the branching
particles of the iron adhere firmly to each other as
though they were joined by clasping hooks, so that
the nitro-aerial spicules are more closely interlaced
with them.

Hence too the reason is obvious why soil that has
been bound fast in the ice of winter becomes more
fertile in the following spring. Doubtless the nitro-
aerial particles from which when closely fixed in its
structure the freezing of the soil results, produce when
set in motion afterwards by the warmth of spring that
effervescence in the bosom of the earth to which the
generation of all-fertilising nitre and the growth of
plants are due, as is shown elsewhere.

Further, that water is frozen by nitro-aerial particles
fixed in it seems also to be confirmed by the fact that
when frozen it is rarified and expanded. 1 am aware
that the ingenious Descartes gives a different explana-
tion of the rarefaction of frozen water. In fact that
eminent man supposes that the aqueous particles when
less disturbed by subtle matter cease to move and
become somewhat curved, from which it results that
they cannot then contract themselves into so narrow a
space as before, when the subtle matter having power
enough to bend them as it pleased was always adapting
their forms to the measure of the places in which they

On Sal Nitrum and Nitro- Aerial Spirit 51

were. But in fact what should force the aqueous
particles set in motion by the subtle matter into other
situations, once they have adapted their forms to the
dimensions of the places in which they are ? For
they should rather retain the same situation by ceasing
to move. For particles adapted to any space would by
no means change their position and recede from each
other with conspicuous force (as happens with frozen
water, which breaks through the strongest glass), unless
some force were applied to those particles.

It is probable then that nitro-aerial particles enter
the pores of the water pointwise and like wedges draw
them somewhat apart from one another so that the
mass of that water has to dilate and swell, the aqueous
particles meanwhile passing from a flexible to a rigid
condition owing to the nitro-aerial particles which are
fixed in them, so that they no longer flow hither and
thither but are joined and, by cohering firmly together,
constitute a solid body.

We note here in passing that as nitro-aerial particles
arrest the movement of aqueous particles and freeze
them, so nitro-aerial particles when secured in their
turn among aqueous particles are as it were fettered
and fixed. And this seems to be the reason why
water is specially adapted for extinguishing flame ;
while yet, on the other hand, sulphureous and nitro-
aerial particles mutually agitate and repel each other.
And hence it is that spirituous liquids which contain
volatile sulphur are never frozen. For if wine be
exposed to the cold of winter all the spirituous and
sulphureous particles of the wine will be driven into
the mid-liquid and only the aqueous particles circu-
lating round them will be frozen. Indeed the nitro-
aerial particles ward off and repel as much as possible
the sulphureous particles and surround them, when

5 2 Mayow

driven into the mid-liquid, as it were with a hostile
blockade.

OF THE RATIONAL CAUSE OF ELASTICITY

So much then for the cause of rigidity. It remains
to inquire why rigid bodies when bent spring back of
themselves to their original shape — for in this lies the
explanation of elasticity. But to pave the way to
our view of the subject the following must be premised.

In the first place, let us consider in how many ways
rigid bodies can be bent, and what sort of change as
to their shape they undergo when bent. Suppose then
a rigid body with its sides equal and parallel such as
that delineated in Plate I., Fig. 4.

In the first place, this rigid body can be bent by
elongating its convex surface while the concave surface
remains of the same length as before inflexion, as is
shown in Plate I., Fig. 5, where let a^ c, 3, w, d^ be the
bent rigid body whose concave surface a^ c, is supposed
to be equal to the length of the rigid body before in-
flexion but whose convex surface b^ ;/, d^ is elongated
by as much as the line 3, ;/, d^ is longer than the line
a^ c.

The second mode of bending a rigid body is that in
which the convex surface is drawn inwards towards
the concave surface — all the surfaces of the rigid body
retaining meanwhile their original length as is shown
in Plate I., Fig. 5, where let a^ c^ -b^ e^ d^ be the bent
rigid body whose convex surface 3, e^ d^ we suppose,
while the rigid body is bent, to be brought just so far
inwards as to be equal to the concave surface a^ c,
that is to the length of the rigid body before inflexion.
And indeed if all the sides of rigid bodies are to retain
when bent their original length, they can be bent in

On Sal Nitnun and Nitro^ Aerial Spirit 53

no other way than by approximating their convex and
concave surfaces.

The third mode of bending a rigid body is that in
which the planes at its extremities are turned towards
each other and also elongated, while the concave and
convex surfaces retain their original length as in Plate
I., Fig. 6, in which let a^ c, b^ d^ be the bent rigid body
whose convex surface 3, d^ I suppose to be equal to the
line ?', 2, or what is the same thing to the length of the
rigid body before it was bent. Then the planes at its
extremities a^ b^ and c, d^ must be turned towards
each other and elongated as is clear from the figure.
For these end planes are inclined at the angle 3, z, e^
and are elongated by as much as the plane 3, /, is
longer than the plane e^ i.

Lastly, a rigid body can be bent by shortening its
concave surface while its convex surface and also end
planes remain of the same length as before ; as may
be seen in Plate I., Fig. 7, where let a^ c, 3, d^ be the
bent rigid body whose concave side «, <;, I suppose
before the inflexion equal to the line between the
extremities e, e. But now when the rigid body is bent
that surface is shortened by the difference between ^, ^,
and ^, c. But we suppose the convex surface 3, d^ to
retain its original length, or what is the same thing to
be equal to the line between the extremities ^, e.

But these observations regarding the various modes
of bending a rigid body will be better understood from
the following example. At the ends of a flexible rod,
let two other shorter rods also flexible be fixed perpen-
dicularly, as in Plate I., Fig. 8. Then let a string
attached to the end of one of the rods be passed
through a hole in the end of the other, as is seen in
the same figure. Then the rod with the two small
rods and the attached string will represent the sides of

54 Mayow

the rigid body delineated in Fig. 4. But now if the
rod be bent so as to represent the concave surface of
the rigid body while the string represents the convex,
and the string meanwhile has been loosened at one of
its ends so that it can be lengthened as the rod bends
so as to remain parallel to it, then the bent rod with
the string parallel to it and the rods at its ends will
represent the rigid body bent in the first manner and
delineated in Fig 5.

But if the string is fastened at each end so that it
cannot be lengthened when the rod is bent, you will
see that the string which represents the convex surface
of the rigid body passes inwards and is drawn towards
the stick or concave surface exactly like the rigid body
bent in the second manner and delineated in Plate
I-, Fig. 5.

Further, if the string be hindered by any force from
being drawn inwardly when the rod is bent, then the
two little rods which represent the end planes of the
rigid body will be drawn inwards towards each other,
as is the case in a rigid body bent in the third manner
and delineated in Fig. 6. But in order that the rigid
body may be exhibited as it is bent in the said figure,
the rods at the end should not only be drawn towards
each other but also lengthened.

Finally, if the rod be bent towards the string so as to
represent the convex side of the bent rigid body, and
the cord which now represents the concave side be
meanwhile shortened, but in such a way as to remain
parallel to the rod, you will have a representation of
a rigid body as it is bent in the last mode in Fig. 7.

We have next to remark with respect to rigid bodies
that their branching parts are so mutually interlaced
and so firmly compacted that the rigid bodies can
neither be lengthened nor shortened without being

On Sal Nitriun and Nitro- Aerial Spirit 55

ruptured. Indeed rigid bodies seem to acquire a
nature of this kind because their pores are crammed
and wholly filled up with certain particles fixed in
them, so that the shape of their pores can by no force
be altered, for in order that anything may be elongated
by extension or shortened by compression its pores
must change to a more oblong shape. For example,
let us put before our eyes a row of parts or branchlets
linked together such as is delineated in Plate I., Fig. i.
If this is to be lengthened or shortened it will be
necessary for the pores of the said branchlets to become
more oblong, as is manifest in Plate I., Figs. 2 and 3,
the first of which represents the pores of the elongated
and the second of the shortened branchlets changed in
both cases, though in a different manner, into a more
oblong shape. If these pores, however, be completely
filled with any solid particles, then in this case neither
the branchlets nor their pores could have their length
extended. And indeed it is probable that nitro-aerial
particles are fixed like little pegs in the pores of rigid
bodies and fill them up, since it is by these being
fixed in the pores of bodies that rigidity is produced,
as was previously shown. And hence it comes about
that neither the pores of rigid bodies nor consequently
the rigid bodies themselves can be either elongated or
shortened. And from this we may infer that when
perfectly rigid bodies are bent they remain on every
side of the same length as before.

These things being assumed, it follows that the
convex surface of a perfectly rigid body will in bending
be drawn towards the concave surface as is the case
when a rigid body is bent in the second manner. For
if it were bent in any other way some one of its
surfaces would have to be either elongated or con-
tracted, as is evident from what has been said. But

56 Mayow

it is implied in our idea of a perfectly rigid body that
none of its sides can be lengthened or shortened.

We may gather from what has been said that the
matter of a rigid body undergoes when bent a notable
compression — and that, especially, at the middle, as is
obvious from Plate I., Fig. 5. For when the convex
surface b^ e^ d^ of the bent rigid body has been brought
inwards towards the concave surface a^ c, the matter of
the rigid body at e must suffer a notable compression.
Hence the reason is obvious why rigid bodies when
bent too much usually break near the middle. Just as
in making bows this alone is attended to that their
middle part be thick and strong enough, while it is of
no consequence if the ends are thinner.

Indeed if a rigid body be so compact and solid that
there are no interstices between its parts, and it
cannot, in consequence, be compressed into less space,
then clearly such a rigid body cannot be bent but will
rather break. For it should be observed that rigid
bodies which can be bent, although their outer surfaces
are extremely solid and firmly compacted, have very
many little spaces in their interior, as is clearly the
case in iron and glass, which are specially rigid. For
when glowing iron or glass is plunged into water, that
they may cool quickly and become rigid, their outer
parts cool sooner than their inner, and on that account
become more rigid and solid. For the nitro-aerial
particles which are in the still heated interior open
little spaces here and there, in order to continue their
motions, and when they gradually extricate themselves
outwards they are detained in the now cooled surface
and render it exceedingly solid, although very many
empty little spaces are left in the interior.

Thus far then of bodies of the greatest rigidity — that
is bodies whose sides can neither be lengthened nor

On Sal Nitrum and Nitro- Aerial Spirit 57

shortened — but since, as is probable, there is nothing
so perfectly rigid, we must suppose that, in the bend-
ing of such rigid bodies as we know, not only does the
convex side come nearer to the concave, but that also
the planes at the ends incline to each other in the
manner already described, also that the convex side is
a little elongated, and lastly that the concave side is
just such a little shortened. For the force by which a
rigid body is bent tends to produce all these results.
For I think it is the case always that if a force seeks
to effect something and there are various ways in
which it may attain the result, while yet there is in all
of them great resistance and difficulty, the force I say
endeavours to perform the thing in these several ways.
Hence since a rigid body can be bent, as was pre-
viously shown, either by the approximation of the
convex to the concave side, or by the elongation of the
one or the shortening of the other, or lastly by the in-
clination to each other of the end planes ; and since
there is at the same time great resistance to the
bending of the rigid body by any of the methods (for
the matter of a rigid body is so dense and compact,
that its sides cannot without difficulty be drawn
towards each other ; its sides also are so firm and solid
that they cannot be lengthened or shortened without
great pressure), hence I say the force by which one
tries to bend a rigid body has enough to do in effecting
its purpose in those several ways. Still, however,
while the rigid body is bending at the same time in all
of these ways, its matter suffers a notable compression,
especially at the middle, as is evident from what has
been said. It should also be remarked here that when
the force by which a rigid body is bent tends to draw
the convex surface towards the concave, it tends also
by compressing the matter of the rigid body to pro-

58 Mayow

trude it towards the sides. Whence it results that
as rigid bodies on bending are attenuated as to their
thickness, so on the other hand they are somewhat in-
creased in breadth.

Since in bending rigid bodies the convex side comes
thus to be lengthened and the concave to be shortened,
the result is that the thinner rigid bodies are, the more
and the more easily can they be bent, for although glass
is very fragile and can scarcely be bent, yet fine threads
of it can be wound round a bobbin and tied in a knot.
But that the reason of this difference maybe understood,
let ^, c, 3, d^ in Plate I., Fig. 9, be a very slender rigid
body whose convex and concave surfaces were equal
before inflexion — but now that it is bent, the con-
vex surface 3, d^ is a little elongated. Let us suppose
that two points e^ e^ are so placed in the convex surface
that the line between the limits ^, e^ is equal to the con-
cave surface ^, c^ which we suppose to be equal to the
length of the rigid body before inflexion. But now if
the convex surface of the bent rigid body be lengthened
out at both ends, at one end from ^ to 5 at the other
from eto ddiS is done in the figure, then there is no
need for this surface being drawn inwardly when the
rigid body is bent — nor consequently that its matter
should be compressed. And yet this is inevitable in
rigid bodies whose surfaces cannot be elongated, as we
have already shown.

Further, if we suppose also that the concave surface
of the rigid body ^, ^, is shortened as much proportion-
ally as the convex surface is lengthened (for it should
be observed that the force by which a rigid body is
bent tends as has been shown above not only to
draw out the convex surface but also to contract
the concave) — say that the concave surface at each
end is contracted to «, and the convex lengthened

On Sal Nitriim and Nitro- Aerial Spirit 59

from e to i — while the rigid body is thus bending
there is no need that the convex surface should move
inwards, and so the matter of a rigid body thus
bent will suffer no compression. And yet the convex
surface is diminished a half less in this case than in
the preceding.

And now we remark that in the case of a very
slender rigid body such as glass threads, whose surfaces
are much nearer each other than in the figure, the
contraction of the concave surface and the elongation
of the convex are extremely small. And hence it is
that the more slender rigid bodies are very easily bent ;
for if their sides, as is the case here, be but a little
lengthened or shortened their matter will scarcely be
compressed at all. On the other hand, let a, c^f^ g^ be
a bent rigid body twice as thick as the former. If in
bending this body, its convex surface is not to be
drawn inwards, nor its matter compressed, the elonga-
tion of the convex surface and the shortening of the
concave must be much greater than in the previous
case. For the elongation of the convex surface has to
be as great at each end as is the distance/, o, and g^ o,
or at least half that distance. For we suppose the line
between the limits o, o, to be equal to the line ^, ^, or
what is the same thing to the length of the rigid body
before inflexion. Now this can be easily illustrated
by means of the instrument delineated in Fig. 8. For
if the string of that instrument be placed near the rod,
so that the apparatus may represent a somewhat
slender rigid body, then if the string be lengthened out
a little, while the rod is bent, it will remain always
parallel to the rod and will not be constrained to move
inwards, and yet if the string be at a greater distance
from the rod you will see that the string, unless it be
drawn out much more while the rod is bending, will

6o Mayow

be drawn downwards towards the rod. But indeed
since the rigid body is as solid and compact in respect
to its external parts as the more slender rigid body or
even more so (for the exterior parts of a thick rigid
body, be it glass or iron, are more quickly cooled than
the interior, so that it is extremely solid as respects
its external surfaces — in so far as the nitro-aerial
particles in endeavouring to escape are detained in
the exterior parts which have now cooled down, and
are fixed there as we have already shown — but this
does not take place in a more slender rigid body, since
all its parts are cooled at nearly the same moment),
hence I say it results that the convex surface of a
thicker rigid body cannot bear to be drawn out as far
as is necessary for bending it without compression of
its parts, so that it is now necessary that the convex
surface of the shortened rigid body should also go
inwards and make, say the Hne ^, m^ h, in the figure ;
and that cannot be done without notable compression.
And the further the two surfaces are from one another,
so much the more must the convex surface pass
inward during the bending, and consequently the
matter of the rigid body will suffer the greater com-
pression ; so that very thick rigid bodies cannot be
bent. And thus it is that a broad and thin plate is
easily bent so far as regards the broad surfaces which
are near each other, while as regards the lateral sur-
faces which are much farther apart it cannot be bent.
While we thus maintain that the power of recoil in
rigid bodies should be ascribed to the compression of
their matter, I would not be understood as thinking
that matter thus compressed endeavoured to extend
itself, for that would be to assume elasticity but not to
explain it, and any one would be ready to ask :
whence arises the power of recoil in the compressed

On Sal Nitrum and Nitro- Aerial Spirit 6i

matter ? But with a view to a further conjecture on
this extremely recondite subject I think it should first
be maintained in regard to motion in general that it
can be produced in no other way than by impulse.
For as regards a natural inclination of inanimate things
by which (in popular belief) they begin this or that
movement spontaneously, I simply cannot understand
it. For I do not know how an elective movement of
that kind can exist without intelligence or at least
sensation. Our opinion indeed is that inanimate
things have no inclination, but that instead of it there
is that power merely by which every thing remains
always as far as may be in the same state. But a
power of this kind implies nothing more than that
inanimate things are unable to dispose of themselves
or to alter their state, but are altogether dependent
upon other things. Whenever then a body is at rest
nothing else can be imagined than that it will remain
for ever in a state of rest, unless as the ingenious
Descartes has remarked a force is introduced from
some other thing. Wherefore elasticity and gravity
from which spontaneous movements, as they are
usually called, arise, must be supposed to be due to
impact of something invisible. But since such things
as are possessed of elastic force and gravity are always
ready to move, provided there is nothing to hinder
their motion, it seems that we should certainly con-
clude that there is some kind of matter which being in
constant agitation always strikes the said things in its
motion and tries to move them. It is long since
Descartes drew attention to such perpetually moving
matter, and indeed there can be no doubt whatever
regarding its existence. For I cannot conceive how
sound, and light, and the like, are propagated where
there is no air unless there exists some fine matter by

62 Mayow

means of which impulses and movements of such kind
are kept up. Should any one ask here what it is
which perpetually agitates that subtle matter, I answer
that it was set in motion when first created and that
there is nothing that can hinder its motion. For we
must imagine that it has no weight at all to stop
its motion, but that it is rather probable that the
weight of bodies is due to its impulse. Nor is this
subtle matter impeded in its motion by meeting with
other bodies, since it must be supposed so thin, and
smooth, and solid as either to pass with ease through
the pores of bodies or to be reflected with its motion
unaffected when it impinges upon their solid particles.
For it is impossible that this very subtle matter should
strike against any soft body. For softness implies a
great number of particles in a loose state of union,
but this matter is so fine that it cannot at a time
touch several particles, and so can only strike one,
and that is hard.

Let us then suppose that this subtle matter occupies
little spaces here and there interspersed among the
particles of rigid bodies and sets up its motion of
circumgyration in these pores without hindrance of
any kind. For it is to be observed that the matter of
rigid bodies, of whatever sort it be, was at one time
soft, tender, and to some extent fluid, so that the
subtle matter was able from the beginning to open
out little spaces in which to set up its motion. But
now when the rigid bodies are bent and their matter
suffers compression, the pores and little spaces of the
bent rigid body are necessarily somewhat contracted,
so that the subtle matter is unable to describe its
circles in these now contracted little spaces, and there-
fore it strikes and impels any particles of the rigid
body which have been pushed into the spaces where

071 Sal Nitrum and Nitro-Aerial Spirit 63

it moves. Meanwhile the subtle matter is reflected
from the parts which it strikes, and dashes instantly
against the particles opposite, to be repelled anew.
And so the subtle matter strikes incessantly the parts
of the rigid body, and its particles which are almost
infinite in number and distributed through the whole
mass of the rigid body all co-operate to restore to their
original shape the pores of the rigid body and conse-
quently the rigid body itself. And in this efi'ort the
explanation of elasticity seems to lie.

We remark here in passing that the force with
which a string that has been violently stretched con-
tracts to its original length arises from the same cause.
For although the string itself may be a loose body, yet
its minute fibres are somewhat rigid and their shape
alters with the extension of the string. But the move-
ment of the contracting string is caused by the effort
of its fibres to revert to their original form.

From what has been said, we may conjecture why
the glass globules with a sharp beak attached to them,
commonly called glass drops, which are formed by
dropping a little molten glass into cold water, burst
with remarkable and almost explosive violence into
the minutest fragments if the fine end of the beak is
broken. Some imagine that the violence with which
the drops burst is caused by the bending and tension
of the parts of the glass. But it is hard to conceive
how the parts of the said glass can be in a state of
tension, since to produce the tension from which
elastic force results it is an indispensable requisite that
the rigid body after it has cooled should be bent by
some force or, what amounts to the same thing,
should be stretched. For in whatever way the heated
rigid body or its parts may be bent or distended
while cooling, they will never be under tension unless

64 Mayow

their form be altered by some force after they have
cooled.

But although I do not think that the parts of the
rigid body are under tension, still it is probable that
that violence with which the glass drops burst is truly
elastic, and that it results as elastic force does from the
impulse of the subtle matter. And it is probable that
this elastic force arises in the following way. When
the small portion of glass glows and is in a sense fused,
its structure is opened to such an extent by the rapid
movement of nitro-aerial and fiery particles, that space
enough exists in it for the nitro-aerial particles and
besides for the subtle matter to execute their move-
ments. But when the molten glass is dropped into
cold water the fiery particles crowded at its surface are
immediately arrested in their motion when they meet
with the water particles, and those in the interior also
soon desist from moving. But it should now be
noticed that when the glass is cooled in this manner
its parts settle down and it becomes itself contracted,
not because these parts of the glass spontaneously
approach each other (for the parts not yet cooled are
not under tension and therefore do not possess a power
of recoil or a motion of restitution, as we have shown
above), but it is rather to be supposed that the sub-
sidence of the vitreous parts arises from this, that the
nitro-aerial particles occupy less space when they
cease from their fiery motion and no longer push the
parts of the glass away from each other, so that the
particles of the glass are forced towards each other by
the pressure of the atmosphere.

But, now, since the outer surface of the said glass
immediately becomes rigid from being rapidly cooled
by the water, it becomes so solid by reason of the
nitro-aerial particles infixed in it, that the nitro-aerial

On Sal Nitrinn and Nitro- Aerial Spirit 65

particles and the subtle matter existing in the interior
cannot as in other cases extricate themselves. Hence
it is that in glass contracted in this way the subtle
matter imprisoned among the minutest particles of
the glass has not room as before for freely continuing
its movements. For resistance is made to the move-
ment of the subtle matter, from two causes ; first,
because the particles of the glass being at rest do not
yield to the movement of the subtle matter as before ;
and secondly, because the particles of the glass in sub-
siding under the pressure of the atmosphere are driven
into the little spaces in which the perpetually agitated
matter carries out its motion. Hence that matter
strikes the particles of glass which oppose its motion
and endeavours to part them from each other. Indeed
the case is very much as if the glass were bent almost
to breaking ; in fact it is to be observed that the
pulsation of the subtle matter is almost capable of
breaking the said glasses, as is evident from the fact
that when drops of molten glass are dropped into
water most of them immediately burst asunder ; and
indeed we must suppose that all the rest just escape
being broken.

Wherefore when the beak of this kind of glass is
broken, the force of the subtle matter, aided somewhat
by the concussion of the whole glass caused by the
fracture of the beak, is now able to draw the particles
of the glass apart and to thrust them out with violence.
I add further that when the glass is broken in any
part, the particles of glass which were previously con-
fined by its extremely solid surface, rush out by the
open door at the very moment when the effort of the
subtle matter begins to take effect, and by this no
small addition is made to its force. And, finally, let us
further consider that the pointed beak of the glass

E

66 Mayow

must be bent before it is broken ; whence it follows
that the matter contained in the beak undergoes com-
pression anew, as was shown above to happen when
rigid bodies are bent. Hence the subtle matter, com-
pressed by the bending of the beak, strikes against all
the adjoining particles of the glass ; but since the
external surface of the glass is more compact and solid
than its interior parts (for when these globules are
formed, the heated and melted glass is dropped into
cold water, so that the external surface is cooled
quickly by the water while the internal parts cool
more slowly), it comes to pass that the compressed
subtle matter can more easily make a way for itself
into the globular part of the glass, as being less com-
pact, than break through the more solid surface of the
glass. And this may 'also be inferred from the fact
that the glass beak can be bent much more and is
broken with greater difficulty than glass under other
conditions. And the reason of this seems to be that
the subtle matter which, when compressed under other
conditions and about to make its escape, bursts through
the particles of the bent glass and drives them out
with violence, now takes its way into the globular part
of the glass (the pyramidal shape of the glass con-
tributing not a little to this) : but the particles of the
subtle matter when pushed from the beak into the
globular part of the glass, effect a greater compression
there, and in consequence the whole glass is violently
and most minutely fractured. For as under other
conditions, if glass or any rigid body is broken, the
parts about the middle, where the matter is most
compressed, are broken into small pieces and fly
asunder, so the matter in the glasses here discussed,
being everywhere compressed, bursts all over.

On Sal Nitrum and Nitro- Aerial Spirit 67

CHAPTER VII

THAT THE ELASTIC POWER OF AIR IS DUE TO
NITRO-AERIAL SPIRIT; ALSO OF THE MANNER
IN WHICH AIR IS IMPREGNATED ANEW WITH
NITRO-AERIAL PARTICLES; INCIDENTALLY OF
THE ELEMENTS OF FIRE AND OF COLD

Thp: experiments of Boyle have proved beyond doubt
that air is eminently elastic and therefore spreads and
expands immensely when relieved from the pressure
of the atmosphere. But it is not so clear to what
cause the elastic force of the air is due. I shall, how-
ever, state briefly the result of my reflections on this
recondite subject.

In the first place, then, I take it for granted that the
air contains certain particles termed by us elsewhere
nitro-aerial which are absolutely indispensable for the
production of fire, and that these in the burning of
flame are drawn from the air and removed, so that the
latter when deprived of these particles ceases to be fit
for supporting fire, as has been shown above.

It must also be admitted that the elastic force of the
air is due to the same aerial particles as those by
which flame is supported — an inference which we
deduce from the fact that air deprived of these nitro-
aerial particles loses elastic force, as will be established
by what follows.

For firstly we have to note, what almost everybody
knows, that if a cupping-glass filled with flame be
applied to the skin, the flame will soon go out and the
space within the cupping-glass will be almost empty,
and as a consequence the skin will be driven into the

68 Mayow

hollow of the cupping-glass by the pressure of the sur-
rounding air. But now let us inquire why the space
within the cupping-glass becomes almost empty
immediately upon the extinction of the flame. One
might readily say here that the fiery and aerial par-
ticles are agitated in the flame with a very rapid motion
and are much rarefied, but that after the extinction of
the flame they cease from their movement and are con-
densed, so that these particles are no longer able to
resist the pressure of the surrounding air. But this
answer does not seem quite satisfactory, for it is prob-
able that air is largely mixed with the flame, since it
supplies it with nutriment, so that not even the
smallest part of the flame is altogether destitute of air.
But if the air were distributed abundantly enough in
the flame, it does not appear that it would be condensed
after the extinction of the flame to the extent required
for rendering the space in the cupping-glass so empty.

Wherefore I think it should be maintained that the
air mixed with the flame is, by the burning of the
flame, quickly deprived of its nitro-aerial and elastic
particles, so that this air not only becomes unfit for
sustaining fire but also loses in part its elasticity.
Hence when a flame enclosed in a glass vessel has
exhausted the nitro-aerial particles of the air, it soon
goes out and the space contained within is like a
vacuum, not only on account of the diminished motion
of the igneous particles, but partly also from the lack
of elastic particles, as will appear more evident from
the following experiments.

For instance, let a burning candle be placed in water
so that the wick may stand about six finger-breadths
above the water, and then let an inverted cupping-
glass of sufficient height be put over the light and
plunged immediately into the water surrounding the

On Sal Nitnim and Nitro-Aerial Spirit 69

light, as is shown in Plate V., Fig. i. Care, how-
ever, must be taken that the surface of the water
enclosed within the glass be at the same level as the
water without. But that this may be attained in the
present experiment, and also in those that follow, let
one leg of an inverted syphon be enclosed within the
cavity of the cupping-glass before it is put into the
water while the other leg projects outside, yet so that
the end of each leg may be above the surface of the water,
as is seen in the said figure. The use of the syphon is
to enable the air enclosed in the alembic, and com-
pressed by the underlying water while the glass is
being let down into the water, to pass out through the
cavity of the syphon, so that the water within may
not be depressed below the level of the water outside,
as it would otherwise be. But when the air ceases to
pass through the syphon (which will happen almost in
an instant) the syphon should be at once withdrawn,
that the air may not afterwards rush through it into
the glass. When these arrangements are made let the
cupping-glass be firmly fixed so that it may descend
no further into the water, and you will presently see,
while the light still burns, the water rising gradually
into the cavity of the cupping-glass.

I will not deny that the ascent of the water arises in
part from the circumstance that when the light is
about to expire, the air enclosed in the cupping-glass
is less agitated and rarefied by the igneous particles
than formerly. But the rise of the water into the
glass must not be ascribed to this cause alone, since it
is partly due to this, that the lamp enclosed in the
glass is, by its own burning, deprived of nitro-aerial and
elastic particles so that the air there is not able as be-
fore to resist the pressure of the atmosphere. And this
will be further confirmed by the following experiment.

70 Mayow

For let any combustible material which will readily
take fire be suspended in an inverted cupping-glass as
large as can be had, as is shown in Plate V., Fig. i (I am
myself in the habit of suspending a bit of camphor to
which a small piece of linen, charred in the usual way
into tinder and dipped in melted sulphur, is attached).
When this has been done, let the inverted cupping-
glass be immersed in the water about ten finger-
breadths so that the water enclosed in the glass may
be at the same level as the water outside, which can be
done, easily enough, by means of the bent syphon
already described ; and lastly, let the water outside be
drawn oflF until the level of the water within is higher
than that of the water outside, so that it may be more
distinctly seen, or better, let the cupping-glass be trans-
ferred to another and shallower vessel by placing
under it a small vessel, big enough, however, to receive
the mouth of the cupping-glass, and then transferring
the small vessel filled with water, together with the
cupping-glass resting upon it, into a suitable vessel
almost full of water. And let the cupping-glass remain
there until the air heated by the hands of the operator
has been condensed to its original state. And then,
lastly, let the height of the water within be noted by
papers affixed here and there to the sides of the
glass by means of a paste made of barley-meal boiled
in water. Now let the cupping-glass be exposed to
the rays of the sun and let the camphor or other com-
bustible matter enclosed in it be kindled by means of
a burning-glass, by first lighting the aforesaid sulphured
linen placed under the combustible matter. When this
has been done you will see the water within descend on
account of the agitation of the fiery particles, and the
rarefaction of the air inside. When the light has gone
out let the cupping-glass and the small vessel on which

On Sal Nitrum and Nitro- Aerial Spirit 71

it rests be removed from the sun's rays, that the air
enclosed in it may cool again and return to its former
condition, and then you will find that the water within
has risen above the point marked at first. And indeed
I have found by calculation that the air has been
reduced in volume by about one-thirtieth by the burn-
ing of the light.

After the smoke of the burning light with which the
cupping-glass was filled had entirely disappeared and
the glass had become as bright within as at first, I tried
to kindle the light in it a second time by throwing the
solar rays upon another piece of camphor, suspended in
the glass in the same way as before, but the experiment
did not succeed — a sufficiently clear proof that the air
had been, by the burning of the light, deprived of its
igneo-aerial particles, so as to be quite unfit for sustain-
ing flame anew. But lest any one should think that the
light could not be kindled a second time in the glass,
because the inner sides of the glass had been dimmed
so much by the smoke of the light previously burned
in it that the rays of light could not be transmitted
through the glass with sufficient intensity, I fasten a
piece of paper about a hand-breadth broad, with its
margins all round coated with the aforesaid paste, to
the inner side of the cupping-glass at the place where
the solar rays are to be transmitted. When the fumes
have entirely vanished this paper is to be pulled off,
by a thread attached to it and extending outside the
vessel, so that the solar rays may pass through the part
of the glass which has been protected from the soot.

It is a further confirmation of our hypothesis that
the air given out from the lungs of animals has its
elastic force diminished in consequence of the loss of
its nitro-aerial particles, as will be manifest from the
followinsf.

72 Mayow

/ Let a moistened bladder be stretched over the cir-
cular orifice of any vessel and tied to it just as the skin
of a drum is stretched ; then let a small bell-jar in which
a little animal, say a mouse, has been put, be accurately
applied to the said bladder by placing a weight upon
the jar lest the animal inside should upset it (as is
shown in Plate V., Fig. 2). When things have been
arranged in this manner it will in a short time be seen
that the jar is firmly fixed to the bladder ; and the
bladder also, at the place where it lies under the jar, is
forced upwards into the cavity of the glass just as if
the jar had been applied with a flame enclosed in it.
And this will take place while the animal is still
breathing. Nay, if the jar be grasped by the hand and
raised, the bladder, along with the vessel, will still
adhere firmly to it unless the vessel is very heavy.
And indeed a little animal placed in a cupping-glass
which is to be fixed to the skin can supply to a small
extent the place of the flame. And from this it is
clear that the elastic power of the air enclosed in the
aforesaid jar has been diminished by the breathing of
the animal, so that it is no longer able to resist the

A pressure of the surrounding air.

But in order that this matter may be better under-
stood, let me submit yet another experiment to the
same effect — an experiment moreover from which it
will be easy to perceive in what proportion the air is
diminished as to its volume when deprived of vital
particles by the breathing of the animal. Thus, let a
small animal placed on a suitable support be enclosed
in an inverted glass, or better, let the animal be put
into a suitable cage and suspended in a glass jar just as
the vessel is suspended in Plate V., Fig. 4. Then let
the inverted glass be sunk a little into the water so
that the water enclosed in the glass may stand at the

On Sal Nitrum and Nitro- Aerial Spirit 73

same level as the water outside, as may be done by
means of the bent syphon already described. When
this is done let the water outside be drawn off a little
in order that the height of the water within may be
better observed. And let it be indicated by papers
attached here and there to the sides of the glass. And
so you will soon see the water sensibly rising into the
cavity of the glass, although the heat produced by
the presence of the animal in the glass, and also
the breath proceeding from it, might be expected rather
to produce an opposite effect.

But we can perceive in the following way the extent
to which the air enclosed in the glass undergoes con-
traction before it becomes unsuitable for sustaining
animal life. For let the space in the glass occupied by
the air when the animal was at first placed in it and
also the space occupied by the same air when the
water has risen in the glass after the suffocation of the
animal be measured, as can be done by pouring water
into those spaces so as to fill them and measuring it —
but warning should be given here in passing that when
these spaces are thus measured everything should
remain in the glass the same as before. And now let
it be ascertained by calculation how much the first
space is greater than the second. For to that extent
the air is lessened as to its elastic force and volume by
the breathing of the animal. And in fact I have
ascertained from experiments with various animals
that the air is reduced in volume by about one-
fourteenth by the breathing of the animals. But
care should be taken in making this experiment that
the animal be placed only a little above, the surface of
the water, for a reason to be afterwards given.

From what has been said it is quite certain that
animals in breathing draw from the air certain vital

74 Mayow

particles which are also elastic. So that there should
be no doubt at all now that an aerial something
absolutely necessary to life enters the blood of animals
by means of respiration. And indeed if the necessity
for breathing arose, as some have imagined, merely from
this that the mass of the blood should be churned and
divided into the most minute parts by the movement
of the lungs, there would certainly be no reason why
an animal, enclosed in a glass vessel in the manner
described, should die so soon, because the air there
avails as much after the death of the animal as before
to inflate the lungs and consequently to churn the
mass of the blood. For as that air is impelled by
the pressure of nearly the whole atmosphere, there is
nothing to hinder it from being urged into the dilated
thorax of the animal, and on this the inflation of the
lungs depends, as we have shown elsewhere.

There is now no reason therefore for denying the
entrance of air into the blood because on account of
the dulness of our senses the vessels by which it enters
cannot be seen. For other ducts which serve to
convey thicker liquids are not seen by the eye until
their different capillaries,'after a passage of some length,
unite in a noticeable canal. For what keenness of
vision has ever beheld the sources of the lymphatic or
lacteal vessels or even of the veins ? How much less
may one discern these aerial ducts which must be very
short and extremely small, for these ducts do not, like
the others, run any considerable distance and at last
join one another, but merely pass separately by a very
short and obscure route through the membranes of
the lungs ; for that the aerial particles should be mixed
with the blood in the minutest and most intimate way,
it is necessary that they enter the blood by vessels or
rather pores almost infinite in number, distributed, here

Oil Sal Nitrum and Nitro- Aerial Spirit 75

and there, through the whole mass of the lungs. And
yet in the lungs, when boiled and dissected, an almost
infinite number of openings resembling most minute
points are seen by the aid of the microscope. But
whether these points are the mouths of capillary
tracheae, or of vessels opening into the blood, I cannot
state with certainty.

Hence it is manifest that air is deprived of its elastic
force by the breathing of animals very much in the
sam.e way as by the burning of flame. And indeed
we must believe that animals and fire draw particles
of the same kind from the air, as is further confirmed
by the following experiment.

For let any animal be enclosed in a glass vessel along
with a lamp so that the entrance of air from without
is prevented, which is easily done if the orifice of the
inverted glass be immersed in water in the manner
already described. When this is done we shall soon
see the lamp go out and the animal will not long
survive the fatal torch. For I have ascertained by
experiment that an animal enclosed in a glass vessel
along with a lamp will not breathe much longer than
half the time it would otherwise have lived.

Nor is there any reason for supposing that the
animal is suffocated by the smoke of the lamp, for
scarcely any smoke will emanate from it if spirit of
wine is used, and indeed the animal will live in the
glass for some time after the extinction of the lamp —
that is, after the fumes have entirely disappeared — so
that it is by no means to be supposed that it has been
suffocated by the fumes of the lamp. But since the
air enclosed in the glass is in part deprived of its nitro-
aerial particles by the burning of the lamp, as has
already been pointed out, it cannot support long the
breathing of the animal, hence not only the lamp but

76 Mayow

also the animal soon expires for want of nitro-aerial
particles.

But the reason why an animal can live for some
time after the extinction of the lamp seems to be this.
It is only by a continuous and moreover an abundant
and rapid stream of nitro-aerial particles that a lamp
is sustained. Consequently if the succession of nitro-
aerial particles be but for a moment interrupted, or if
they are not supplied in due abundance, the flame will
immediately sink down and expire. Hence as soon as
the nitro-aerial particles begin to come but sparsely
and slowly to the flame it presently goes out. But a
smaller ration of aerial nourishment and that intro-
duced at intervals will suffice for animals ; so that an
animal can be sustained by the aerial particles remain-
ing after the extinction of the flame. It supports this
view that the movement of the subsiding lungs con-
duces not a little to draw in the aerial particles if any
remain in the said glass and to carry them into the
blood of the breathing animal. Hence it results that
the animal does not die until the aerial particles have
been entirely exhausted. And hence it is that the air
in which an animal is suffocated is contracted in
volume by more than twice as much as that in which
a lamp goes out, as was formerly pointed out.

Further, having suspended combustible matter in a
glass vessel beside an animal, I tried to ignite it by
means of a burning-glass after the animal was suffo-
cated, and that that might if possible succeed, I pro-
tected from the breath of the animal the side of the
glass through which the solar rays were to be
transmitted, by means of a piece of paper fixed to it
as already described. But the experiment did not
succeed. I shall not, however, make any certain pro-
nouncement in regard to this, because wintry weather

On Sal Nitrnm and Nitro- Aerial Spirit 77

and a sky almost constantly wrapped in clouds pre-
vented me from repeating the experiment. It is
probable, however, that air which is unsuitable for
supporting life is also incapable of producing flame,
since a greater quantity of aerial particles is needed
for the burning of a lamp than for sustaining life. But
it is to be noted here that although flame and life are
sustained by the same particles it is not on that
account to be supposed that the mass of the blood is
really on fire, as will be shown in the next chapter.

But assuredly difficulties by no means slight occur
in connection with what has been said. For, in the
first place, how should it be that an animal or a lamp
enclosed in these glass vessels is unable to survive while
a sufficient abundance of air is contained in them ?
For the water underneath ascends into a part only of
these glasses and the remaining space is filled with air,
and that air although diminished in volume is yet
able to resist the pressure of the surrounding air.

Further, in what way shall we suppose that the air
in the aforesaid glasses loses its elastic force ? For we
must believe that air is contained in them in undi-
minished quantity after the extinction of the flame
and the death of the animal. For the aerial particles
are not annihilated by the burning of the flame or the
breathing of the animal. Nor are they driven out of
the glass, for neither air nor any other elastic matter
mixed with it is able to penetrate glass, as we have
indicated above ; for otherwise the pressure of the air in
the glass could not be removed or diminished by any
suction, inasmuch as the air or the elastic matter would
immediately enter the glass from which the air had
been exhausted and fill the space left by the air, especi-
ally since the pressure of the surrounding air assists
towards their entrance.

78 Mayow

Since then the air still remains in these vessels, shall
we suppose that it has been condensed and that the
ascent of the water results from this ? But neither is
this the case, for we note that the water in the glass
in which the light has gone out rises above its former
level while the air is not yet completely cooled.
And indeed the heat caused by the presence of the
animal is fitted to produce rarefaction rather than
condensation. Besides if the air underwent no other
change than condensation only, there is no reason why
the lamp or the animal should not have been sustained
by it. Should any one happen to say that the elastic
force of the air was diminished by the respiration of
the animal because some part of the air entered the
blood of the animal, I reply that the blood of the
animal, when it was enclosed in the glass at first, con-
tained an equal and even a larger supply than after-
wards of aerial and elastic particles, and it therefore
follows that some elastic particles must pass out from
the blood of the animal into the glass pari passu with
others that enter in, and consequently that elastic
particles must be contained in the glasses after the
animal has breathed for some time in it in no less
abundance than before. Nay, even although more
aerial matter should enter the blood of the animal
than is given out from it, still it would continue to
exist in the glasses, and in accordance with its elastic
nature would occupy as much space as otherwise.

But, to make a conjecture on this difficult subject, let
us consider in how many ways the elastic force of
bodies may originate. And, in the first place, we
notice that the particles of all bodies whatever, when
set in motion, open out and seek to expand into a
larger volume, inasmuch as they require more space
than before for executing their motions. And indeed

On Sal Nitrum and Nitro-A'erial Spirit 79

it is probable that some subtle and nimble matter
interspersed with aerial particles and continually
agitating them conduces not a little to the expansive
force of the air. And in this way the elastic force of
the air seems to be increased when heat is com-
municated to it, for the nitro-aerial particles (from
whose agitation we have concluded elsewhere that
heat arises) strike the aerial particles and keep them
in motion ; but these when moved tend to unfold.
But indeed it is scarcely credible that the elasticity of
air depends on this cause alone ; because when the
lamp or the animal is shut up in the aforesaid glasses,
the aerial particles there, being heated by the flame or
by the presence of the animal, would necessarily be set
in motion, and therefore the elastic force of that air
would be rather increased than diminished, if it
resulted merely from the movements of aerial
particles.

2. Elastic force, or the power of recoil, arises from
the bending of rigid bodies inasmuch as these when
bent strive to return to their original form. And
indeed it is probable that the elasticity of the air
results mainly from this very cause. It would certainly
be reasonable to suppose that nitro-aerial and fiery par-
ticles are fixed in the aerial particles themselves and
constitute the more active part of them. For although
aerial particles are very minute and are commonly re-
garded as most simple and elementary, still it seems to
me necessary to suppose that they are compound and
that some of their parts are branchy and adhere firmly
to each other as if by mutually clasping hooks ; while
others are extremely subtle, solid, smooth, agile, fiery
and truly elementary, and that these when firmly
fixed among the other particles make them rigid in
much the same way as rigidity and elasticity are in-

So Mayow

duced in iron by nitro-aerial particles communicated
to it from fire, as I previously endeavoured to show.
I am also of opinion that the elastic force of the air
consists in this that the particles of the air becoming
rigid, and compressed and bent by the weight of the
incumbent atmosphere, strive to spread themselves
out.

Certainly the rigidity of the aerial particles seems
to be the cause of their not entering the minute
pores of bodies so readily as the grosser particles
of watery liquids, as could be established by very many
experiments. For although aerial particles are very
minute, yet on account of their rigidity they cannot
adapt their forms, like the flexible particles of watery
liquids, to the tortuous passages of bodies. Hence also
it seems to come about that water ascends in very
minute glass tubes and also into the pores of a sponge
and other things of that kind. For although rigid
particles of air cannot enter extremely fine little pores
of that sort, yet water is forced up into them as into an
empty space by the pressure of the remaining air.

To this I add further that the rigidity of aerial
particles appears to contribute not a little to the
kindling of fire, inasmuch as the nitro-aerial particles
on being violently torn from the particles of the air in
which they were firmly fixed are thrown into very rapid
motion, for otherwise I do not see how the nitro-
aerial particles could begin so rapid a movement. But
of this more will be said afterwards.

But now it is probable that aerial particles when
mixed with flame lose their elasticity in the following
manner. Thus we must suppose that the sulphureous
particles of fire, when thrown into violent agitation,
approach all the particles of air which are nearest
them, and impinge on the nitro-aerial particles which

On Sal Nitriim and Nitro- Aerial Spirit 8i

the air contains and by their coUision drive them
forcibly out, and that at last from these, violently
ejected and in vehement commotion, fire is produced,
as will be shown more fully below.

Further, it is a reasonable supposition that the aerial
particles, deprived in the manner aforesaid of nitro-
aerial particles, become not only unfit for sustain-
ing fire but also change from rigid to flexible and in
consequence are deprived of their elasticity, for that
the rigidity of aerial particles is due to nitro-aerial
particles fixed in them, while their elasticity results
from their rigidity, I have already endeavoured to show.
Indeed aerial particles when passing out from flame
appear to be in a condition very similar to that of a
steel plate which is slowly cooled after it has been
heated, for this also loses its elasticity as the fiery
particles extricate themselves from its structure, and
becomes moreover incapable of having, as before,
sparks struck out of it by flint. And in fact fire seems
to be nothing else than a collection of very minute
sparks very densely struck out from aerial particles by
the collision of sulphureous particles. For the case is
very much as if we were to suppose that innumerable
little particles of flint and steel collide at the same
instant with each other. For as aerial particles are
solid bodies and are rigid like steel plates, they seem
to be fit enough for having fire struck out of them.
Hence if the sulphureous particles are too volatile and
fine the flame produced by them is very sluggish, such
as is the flame of burning spirit of wine or the very
feeble and almost harmless fires which are produced by
the sulphureous effluviae of animals, for since these
extremely fine and volatile sulphureous particles only
collide in a feeble and gentle manner with the aerial
particles, they are scarcely able to strike effectively

F

32 Mayow

against the nitro-aerial particles and set them in
igneous motion.

I add further in confirmation of what has been said,
that the nitro-aerial particles to which the elastic force
of the air is due are fixed in the aerial particles them-
selves and are torn from them by the burning of a
lamp or by the breathing of animals ; for that the
nitro-aerial and elastic particles which are lacking in
the afore-mentioned glass vessels are neither air itself
nor some material interspersed among its particles, has
been shown above, and therefore it must be concluded
that the elastic particles are implanted in the particles of
the air themselves and constitute their more active part,
and that it is in fine because these are driven out from
the aerial particles by the burning of fire or by the
breathing of animals that air becomes quite effete and
destitute of elastic force.

That the igneo-aerial particles are not air itself pure
and simple, but only its more subtle part, may be
inferred besides from this, that nitro-aerial particles,
whatever they be, exist in nitre and constitute its fiery
and aerial part, as was shown above. But who can
imagine that air itself resides in such abundance in
nitre as is required for its burning in a place void of
air ? If spirit of nitre be poured upon any fixed salt
when taken fresh from the fire, nitre will be produced
by their union ; but it is not to be supposed that air is
present in such quantity in either of these principles,
nor can we believe that air coalesces along with
these principles in the generation of nitre. Nor is it
probable that air without any force applied to it would
condense to such an extent as would have to be
supposed in the case of nitre if its burning resulted
from air residing in it. For to the production of so
impetuous a flame as is produced by a small morsel of

Ofi Sal Nitrum and Nitro- Aerial Spirit 83

■nitre, no mean supply of air is required, but that so
much should be imprisoned in a small piece of nitre is
very unlikely, especially as it is only such air as is
possessed of a very high degree of elasticity that is
suitable for the production of flame. But these points
will be still further established by the following experi-
ment.

For instance, let spirit of nitre and also salt of tartar,
or any other fixed salt dissolved in a small quantity of
distilled water, be placed in separate glass vessels and
•enclosed in another sufl5ciently large glass vessel from
which the air is afterwards exhausted, as far as possible,
by means of an air-pump (indeed in the experiment
made by me the air was almost entirely pumped out).
When this is done, if any aerial or elastic substance
be present mixed with the aforesaid liquids, it will
escape in the form of bubbles when the pressure of
the ambient air is withdrawn. When the bubbles, if
there be any, no longer escape from the liquids (for it
is to be observed that from nearly every liquid when
in a place void of air small bubbles are wont to rise)
let the aforesaid liquids be mixed, and an intense
effervescence will immediately be produced. Let
everything remain in this condition until the action
has entirely ceased, and then, lastly, let the mixture be
removed and evaporated at a mild heat to the dryness
of salt, and so at the bottom of the glass we shall find
nitre generated in an airless place, which in accordance
with the nature of nitre will, if placed on a burning
coal burst into flame ; and yet it is by no means to be
supposed that air is present in nitre produced in this
way. Further, if nitre itself dissolved in distilled water
be put in a place empty of air, air in the form of
bubbles scarcely escapes at all from the solution —
•certainly in a less degree than from common water —

84 Mayow

a clear enough proof that air is not so densely enclosed
in nitre.

It is thus evident that the igneo-aerial particles
common to nitre and air are not air itself, but only
certain very subtle particles which fixed in air and in
nitre constitute their more active and fiery part. Indeed
it is probable that igneo-aerial spirit is fixed in the saline
particles of nitre very much in the same way as in the
aerial particles, and that it is in consequence of their
being violently torn from both kinds of particles and
thrown into violent agitation that fire is produced.

It will not be difficult to understand from this hypo-
thesis of ours why the water ascends in a glass in
which a lamp or an animal is enclosed, although air
exists in it in the same abundance as before, and there
is no reason to suppose' that it has condensed. For
no other conception is possible than that the elastic
force of the air has been diminished, and that this
is due to a certain change wrought in the aerial
particles themselves. But what that change should
be, which diminishes the elastic force of the air, unless
we suppose that the particles from being rigid become
flexible, I confess that I do not understand.

Further, in what has been already said the reason is
to be sought why lamp and animal when placed in the
aforesaid glass vessels expire even when air in sufficient
abundance seems to be contained in them. It must
not be supposed here that of the air enclosed in those
vessels a part has been entirely consumed while the
rest remains unchanged, because if that were so there
would be nothing to hinder the animal from still
breathing in it. But it must rather be thought that
nearly all the particles of the air have undergone some
change, and that they have been deprived to such an
extent of nitro-aerial particles that the air has become-

I^K wouJ
I^H unali

071 Sal Nitrum and Nitro- Aerial Spirit 85

•quite unfit to sustain life and flame. But then you will
say that the air enclosed in the glasses is still possessed
of sufficient elastic force to resist the pressure of the
atmosphere, so that it would seem not to have been
deprived of its nitro-aerial and elastic particles. And
how then can it be that an animal or a lamp cannot
be sustained by it ? Nay, I have ascertained that the
air in which an animal or a lamp has expired is
possessed of no less elastic force than any other air,
for when the pressure of the atmosphere is removed
it expands with no less vigour than common air,
as will be shown in Chapter X. But this seems
flatly to contradict what has been said on this matter.
The answer to be given to this difficulty is, I think,
that the elastic force of the air referred to does not
result from the elasticity of its aerial particles being as
intense as that of unaltered air, but rather from this,
that as aerial particles when deprived of nitro-aerial
particles become less rigid, so they are also more bent
by the pressure of the atmosphere ; but a weaker rigid
body, provided it has been greatly bent and stretched,
will have no less elastic force than a stronger rigid
body less bent by the very same force. It should be
also noted that the elastic force of the said air results
in part also from this, that as that air deprived of
elastic particles is reduced to narrower space, aerial
particles in air of this sort are aggregated in greater
abundance and more densely than in common air.

Here we remark in passing that if the elastic force
of the air resulted from certain agile particles inter-
spersed in it, and if these were exhausted by the
breathing of the animal or the burning of the lamp,
then air in which an animal or a lamp has been enclosed
would by no means expand with as much force as
unaltered air. So that even by this it is clearly proved

86 Mayow

that aerial particles are altered in some way by the
breathing of an animal or the burning of a lamp, and
that they contract in consequence into less space, as
was previously said.

From this it appears to be established that aerial
particles are not fit to sustain fire and life unless they
possess a certain degree of elasticity and rigidity, since^
in so far as they are less rigid, they do not contain
nitro-aerial particles in suflftcient abundance nor can
these be driven out or drawn out quickly enough.

It is also clear from the aforesaid hypothesis why air
passes up in a continual stream to support combustion.
For I do not think that this should be ascribed merely to
the rarefaction of the air mixed with the flame : but
because the aerial particles mixed with the flame are
deprived of nitro-aerial particles, and therefore also of
elasticity, it comes about that they are no longer able
to resist the pressure of the ambient air. Hence such
particles of air as are nearest press into the place of
the ignited particles of the air and drive them up-
wards, since they have lost not only elasticity but also
their former weight in consequence of the disruption
from them of the extremely solid nitro-aerial particles.
And thus one particle displaces another and the flame
is renewed by a fresh access of air. The following
experiment points also to the same conclusion, viz. : — If
a small animal such as a mouse or a bird is enclosed in
the manner aforesaid at the top of a glass vessel it will
die much sooner, and the water underneath will rise
much less than if the same animal had been placed in
the lower part of the glass. This will be very manifest
if two birds or two mice are enclosed at the same time,
one in the upper and the other in the lower part of
the glass ; for in this case the animal put in the
lower part of the glass will for some time survive the

On Sal Nitriim and Nitro-A'erial Spirit 87

other. It must not be supposed here that the vapours
expired by the animal occupy the top of the glass and
exclude the air from that part ; for these vapours
soon condense and adhere to the sides of the glass ;
for otherwise the underlying water would be depressed
by them. But it would be reasonable to think that
the particles of air expelled from the lungs of animals
become lighter, because the nitro-aerial particles are in
part removed from them, and that they rise in conse-
quence to the top of the glass ; and that, being more
densely crowded there, they are capable of resisting
the pressure of the air below and of excluding it, but
are nevertheless unfit to sustain life ; while at the
same time the air at the bottom of the glass remains
unchanged and the animal placed there is still able to
breathe. It is also worthy of notice that when a small
animal, say a mouse, is shut up in a glass and suffers
from want of air, it turns its mouth hither and thither
in an upward direction in quest of breath ; but when
it perceives that it suffers more there from want of
breath it is wont to bring its mouth downwards, and
when it gets a little refreshment there it pushes its
mouth as far down as it can into the glass and keeps it
there.

As an animal, so also a lamp expires sooner when
placed in the upper than in the lower part of the
glass, although this should perhaps be ascribed in part
to the smoke which occupies the top of the glass. Nay,
if an inverted bell-jar be suspended in the air and then
a lamp from which scarcely any smoke proceeds be
.placed in it, you will soon observe the lamp going
out, because the air contained in the glass is soon
rendered incapable of sustaining fire on account of the
burning of the lamp. But as it is lighter than the rest
of the air, the surrounding air forces it upwards and does

88 Mayow

not easily permit it to descend out of the glass. So that
it may be clearly inferred that air is deprived, by respir-
ation and by the burning of fires, of certain solid and
heavy particles, because it becomes lighter when it
passes out from flame or from the lungs of animals.

Here one is led to admire the providence of the
highest and best Artificer by whose most wise counsel
it has been arranged that air, when deprived of its
nitro-aerial particles and vital spirit, should lose at
once its elasticity and its weight, so that it is borne
aloft by the elastic force and pressure of the remaining
air and fresh air comes in place of the effete ; for
otherwise there would be no society at all of men
or even of animals, for we should be obliged to spend
our lives single and separate, namely, where a ration
of nitro-aerial spirit sufficient for sustaining life might
be obtained for each. And indeed between mortals
there would be perpetual strife about the acquisition
and the determination of the boundaries not so much
of fields as of tracts of air. Moreover the life of each
would be a sort of perpetual pilgrimage, inasmuch as
we should find it necessary to wander by night and by
day, through the world and in desert places, not so
much to gain wealth and foreign dainties as to hunt
after aerial nourishment, and to banish ourselves far
to avoid the popular breath. But how much better
has our best Father consulted for us, who has fashioned
this air which surrounds us with such skill, that nitro-
aerial spirit, the most necessary Elixir of life, should
come to us everywhere of its own accord — nay, even
rush uninvited into our very mouths and inmost
vitals.

On Sal Nitrum and Niiro- Aerial Spirit

HOW AIR WHEN DEPRIVED OF NITRO-AERIAL
PARTICLES IS SUPPLIED WITH THEM ANEW

Since aerial particles, whether by the burning of
fires or the respiration of anipials, are deprived in the
manner aforesaid of nitro-aerial particles, let us con-
sider how it is that air is not at last all consumed by
the burning of fires and the breathing of animals, or
at least rendered so effete as to be no longer able to
sustain flame and life. As to this, it may be supposed
that air when deprived of nitro-aerial particles and
therefore also of its elasticity and weight (as was pre-
viously shown) is impelled upwards by the pressure of
the rest of the air, and that when raised on high it is
then impregnated anew with nitro-aerial particles.
For indeed it is probable that nitro-aerial particles,
being extremely small and volatile, float in the higher
regions of the air, and that when collected there in
sufficient abundance they constitute, in accordance
with their diverse conditions, the elements either of
fire or of cold.

With regard to the element of fire, it is probable that
it dwells in the very body of the sun, which appears
to be nothing but an immense chaos of nitro-aerial
particles carried round in a perpetual whirl with the
swiftest motion. Indeed, I think, there is very little
difference between the light of the sun and its rays
collected by means of a burning-glass, in which nitro-
aerial particles are engaged in igneous motion without
accompanying sulphureous particles, as we have else-
where indicated. For although sulphureous particles
are required at first to put nitro-aerial particles in
motion and to kindle sublunary fires, still we must
suppose that the nitro-aerial particles in the sun, not

90 Mayow

now entangled in terrestrial particles but free from
every kind of impediment, will continue to eternity
their motions, once started, without the aid of sul-
phureous particles ; since, indeed, inanimate things
will never suspend their movements unless they are
hindered by some cause^ Further, we must suppose
that nitro-aerial and sulphureous particles never
remain long in the same place, since they mutually
ward off and repel each other in consequence of a
natural antagonism ; and hence it is that there must
be a continual supply of nitro-aerial and of sulphureous
particles for producing sublunary fire. Yet since the
solar light has lasted for so many ages, it is probable
that nitro-aerial particles, free from the presence of
sulphureous particles, move with the greatest velocity
in it. The rays of light will be considered later.

As nitro-aerial particles agitated with swiftest motion
constitute the solar body and fiery chaos, so probably
those pretty near the sun move with their velocity
somewhat abated and are intensely hot without burn-
ing. But at a greater distance from the sun ; namely,
in that region of the air which is commonly called
mid-air and is near the poles of the world, it is probable
that they cease altogether from their whirling move-
ment and are either altogether at rest or advance
pointwise, erect like spears, and that in this state
they constitute that other element of cold. For it
appears to me that we must certainly maintain that
cold is something positive and does not consist in this
merely that the particles of bodies cease from all
motion, as some have imagined ; for the effects of
cold are of such a kind as cannot result from mere
privation of motion, as we have shown above. Moreover,,
that nitro-aerial particles are lodged in ample enough
plenty in mid-air is evident from the fact that that

On Sal Nitrum and Nitro- Aerial Spirit 91

region is extremely cold and that vapours to some
extent freeze in it. For the air in the middle region
is at least as cold as that which rests on the top of the
loftier mountains, which in fact does not permit the
snow there to melt even in mid-summer, as was
remarked by the illustrious Descartes. But I have
endeavoured to show above that intense cold and the
congelation of vapours are due to nitro-aerial particles.
Further, that nitro-aerial particles are crowded in the
highest region of the air seems to be confirmed by the
blue colour of the sky ; for as nitro-aerial particles,
when urged with swiftest motion, glow and flame, so
when they move more slowly, or when their motion
ceases altogether, they assume a blue colour. And it
is an indication of this that the flame of sulphur is
blue ; for the nitro-aerial particles do not move so
swiftly in it as in other flames, as has been elsewhere
stated. And hence it would seem that when flame is
about to expire in subterranean crypts, or even from
the lack of sulphureous nutriment, the nitro-aerial
particles in it do not shine brightly as in other
circumstances, but take a blue colour on account of
their diminished motion. To these I add, lastly, that
iron and other very rigid substances of the same kind
appear blue when polished on account of the nitro-
aerial particles densely fixed in them.

These things being admitted, it is reasonable to
suppose that aerial particles when deprived, whether
by the burning of fire, or by the breathing of animals,
or in any other way, of their nitro-aerial particles and
consequently of their weight and elasticity, are driven
upwards by the pressure of the rest of the air, and
that they ascend until they arrive where nitro-aerial
particles moving with the greatest rapidity constitute
the element of fire : further, that the aerial particles on

92 Mayow

-entering the fiery element in the manner described,
immediately glow and are impregnated anew with
nitro-aerial particles, and are moreover rendered heavier
by the accession of the nitro-aerial particles (just as
antimony when calcined by the solar rays is in-
creased in weight on account of the nitro-aerial
particles infixed in it, as has been elsewhere shown) :
and, finally, that the nitro-aerial particles when impreg-
nated in that way and made heavier are by their own
weight borne downwards to the coldest region of the
air, and being rapidly cooled there become extremely
rigid and acquire anew resilient force. For the case
here seems not to differ much from what happens
when soft and inelastic iron is made to glow by putting
it into the fire, and i^ then immediately cooled by
plunging it into cold water, so that it thus recovers
its rigidity and resilient force.

It is besides probable that the aerial particles, when
made rigid in the manner aforesaid and borne down-
wards by their weight, are likewise in some degree
bent by the weight of the superincumbent air, so that
they no longer move straight like arrows but begin to
rotate. Hence it is that they at last, like the steel
spring which sets automata in motion, are bent in
multiple convolutions and crowded together. And
thus, it seems, there ultimately arises in the aerial
particles that conspicuous elasticity and tendency to
expand indefinitely.

As regards the descent of aerial particles they are
probably not borne straight down, but obliquely
towards the poles. For the continual ascent of
vapours and of air which goes on in the meridional
region, on account of the very intense heat there and
the rarefaction of the air, hinders their straight
•descent ; so that, returning obliquely from the poles,

On Sal Nitriim and Nitro- Aerial Spirit 95

they move towards the south till at last they reach the
lower earth for the various needs of animals. And
this seems to be the reason that the north wind is very
dry and cold, since it brings with it air which is heavy
with nitro-aerial particles and these extremely cold and
dry. And as aerial particles are thus raised aloft when
deprived of nitro-aerial spirit and being then anew
impregnated with it return thence to the lower regions^
the aerial particles seem to circulate like a macrocosmic
blood in a perpetual circuit, and even the air itself, as
in its circulation it takes in nitro-aerial spirit, in some
sense breathes.

CHAPTER VIII

OF NITRO-AERIAL SPIRIT IN SO FAR AS IT IS
BREA THED BY A NIMA LS

Hitherto we have treated of nitro-aerial spirit and
its effects upon plants and other natural things — it
remains for us to inquire into the office it fulfils in
the case of animals. In our treatise on Respiration
published some time ago various considerations in-
duced me to maintain that the chief use of respiration,
that, namely, which makes it so necessary, is that
particles of a certain kind, absolutely necessary for the
support of animal life, may be separated from the air
by means of the lungs and mixed most minutely with
the mass of the blood ; and in confirmation of our
opinion we brought forward in the previous chapter
experiments by which it was shown that the air
expelled from the lungs of animals is deprived of

-94 Mayow

certain elastic particles and in consequence undergoes
contraction.

Further, I attempted to show that the elastic force
of inspired air is diminished because the nitro-aerial
particles which are extremely subtle and nimble are
extracted and in a sense struck out from the aerial
particles. But let us now investigate how this is
done.

In regard to this point I for some time suspected
that nitro-aerial and elastic particles are struck out
from the aerial particles by the special structure of the
lungs. But on more full consideration of the matter I
prefer the view that aerial particles enter the mass of
the blood and are there deprived of their nitro-aerial
particles, and in consequence partly lose their elastic
force, a view which is confirmed by the following
experiment.

Thus let a rod equal in length to the diameter of a
glass bell-jar at its widest part be put inside it, and
placed transversely and drawn downwards till both
ends of the rod lean upon the sides of the glass and
are supported by them, as is shown in Plate V., Fig. 4.
Next let an earthenware vessel, glazed inside and
capable of holding about four fluid ounces, be hung
from the transverse rod by an iron hook attached
to it, and let it be about half-filled with spirit of
nitre. Further, let some small pieces of iron, tied
together into a bundle and suspended by means of a
string from the rod, be made to hang directly over the
vessel (the string moreover ought to be of such a
length that its other end may reach to the mouth of
the glass and hang outside, in the manner shown in the
figure). These arrangements made, the mouth of the
inverted bell-jar should be sunk in the water about
iive finger-breadths, yet so that the water within the

On Sal Nitrum and Nitro- Aerial Spirit 95

bell-jar may be at the same level as the water outside,
as may be done by means of a syphon, the form
and mode of use of which were described in the
preceding chapter. Then let the water outside be
drawn off until it is lower than the water inside by
about three finger-breadths. And let everything
remain thus until the air enclosed in the glass, heated
by the hands of the operator, has returned to its former
state. And then, lastly, let the height of the water
within be noted by papers attached here and there to
the outer surface of the glass, as is shown in the
aforesaid figure.

And now let the aforesaid small pieces of iron be
lowered by means of the string, the end of which
hangs outside, into the vessel which contains the
spirit of nitre. And so a very intense action will
soon be excited and the water within will at once be
depressed by the vapours thence arising.

After action of this sort has gone on for the third
part of an hour more or less, or rather when the
water within has been depressed about three finger-
breadths by the vapours produced, let the pieces of iron
be lifted out of the vessel by means of the aforesaid
string. This done, after a short time you will see the
water within gradually rising, and in the course of an
hour or two you will see it far above the height first
marked. For the water which was quickly depressed
by the aforesaid vapours about three finger-breadths
below the point first marked, now rises some three
finger-breadths more or less above it ; so that about
a fourth part of the space in the glass which was
previously occupied by air is now occupied by the
water rising within. And indeed the water which has
risen in this way in the glass will not, even after a long
time, fall to the original mark.

96 Mayow

So that clearly we must conclude that the air con-
tained in the glass has its elastic force diminished by
about one-fourth part, in consequence of the said
action produced by the spirit of nitre encountering
the iron. Hence it is unable to make the same resist-
ance as previously to the pressure of the atmosphere^
and consequently the water underneath is impelled
upwards into the glass.

Further, after the vapours in the said glass have
been as far as possible condensed and the water inside
does not rise any higher, let its height be indicated as
before by pieces of paper. Then let the iron be
lowered a second time into the vessel containing the
spirit of nitre, that action may be excited anew. But
that this may the better succeed, an ample supply of
spirit of nitre ought to be put into the vessel, or
rather two vessels containing spirit of nitre, and also two
small portions of iron, should be suspended in the glass.
When the water sinks anew about five finger-breadths
in consequence of the vapours produced, let the iron
as before be taken out of the vessel, and when this is
done the water will gradually rise in the glass, yet not so
quickly nor so far as the first time. For the water
which rose after the first action about six finger-
breadths, and far indeed above the height first marked,
will only rise after the second, even should it be more
intense, some two finger-breadths more or less. Nay^
it will never rise to the mark from which it fell. If the
action be repeated a third time the result will be just
the same as in the second.

Now it seems extraordinary that the water which,
after the effervescence first excited, was raised far above
the height from which it sank, should after the second
action, though brought about in the very same way,
not even recover its former height. For what are

On Sal Nitrum and Nitro- Aerial Spirit 97

clearly opposite effects seem to be produced from the
same cause. Nor was any error committed in making
the experiment, for when often repeated the result
was always the same.

But now to submit our views in explanation of the
phenomenon, it is in the first place probable I say that
not only the air which was contained in that part of
the glass in which the water rose after the first action,
but that nearly all the air in the glass was impaired
by the first action. For we notice that in about two
hours after the said action the water had risen so as to
occupy a fourth part of the glass more or less. But it
is not to be supposed that in that space of time the
exhalations or vapours produced by the action were
entirely condensed. Nay, they will never entirely
become liquid, as will be shown below. Let us
suppose then that this exhalation is contracted to the
extent of a half by condensation (for I have ascertained
in a way to be described below that exhalations of that
kind will only condense to the extent of about a half
in so short a time as that in which the water rose in
the glass), and it follows that the space in the glass,
including that into which the water did not rise, is
about half occupied by exhalations not yet contracted ;
since this has undergone a contraction equal to half
the space which is left in the glass before the water
could rise in it.

And in this a reason must be sought for the water
not rising, after the action set up the second time,
above the mark from which it was depressed. No
doubt the effervescing particles which issued from the
previous action being mixed in great profusion with
the aerial particles, impaired them in the way to
be described below ; and the water in consequence
rose into the space which was left not only by the

G

98 Mayow

condensation of the exhalations but also by the re-
moval of the air. But since the air in the glass was for
the most part impaired by the first fermentation, or
rather had its elastic force diminished as far as possible,
hence it is that the water, after the action brought
on the second time, ascends in the glass only to the
extent that the exhalations produced undergo con-
densation, and consequently much less than in the
previous case. And since these exhalations will never
be completely condensed, it follows that the water will
never rise to the point from which it was depressed.

As to the manner in which the air contained in the
aforesaid glass lost its elastic force, it is not to be
supposed that it was condensed on account of being
cooled by the saline exljalations, for the water rose in
the glass while it was still warm from the action.
Nay, if the glass be warmed by placing it near the
fire so that the water contained in it may be rarefied,
the water underneath can yet scarcely be depressed to
the level first marked, even when the heat is intense ;
and when the glass cools it will rise again to its
former height.

Nor is it probable that the air coalesces with the
particles given off in the action and is as it were
coagulated, since it will not submit to so much com-
pression unless under a very intense force. Further,
these effervescing particles are turned into a sort of
vitriol which remains under the form of a liquid, but
it is by no means probable that air in such quantity
can be imprisoned in so small a portion of liquid, as
was more amply stated in another place.

Wherefore it is reasonable to suppose that the
aerial particles, inasmuch as they are rigid, are rubbed
among the fermenting particles in the glass, and
broken perhaps into very minute parts, so that the

On Sal NitrtLm and Nitro-A'erial Spirit 99

nitro-aerial and elastic particles are struck out of them,
and the air consequently is deprived of its elasticity,
and reduced to smaller volume, as was explained in the
previous chapter.

Aerial particles indeed appear to lose their elastic
force in the aforesaid action very much in the same
way as in fire, which has been elsewhere shown to be
nothing but a very impetuous fermentation. And
indeed it is probable that the heat produced by the
aforesaid action and also by others of the same sort, is
due at least in part to nitro-aerial particles struck out
in that way from the air. And this seems to be con-
firmed by the fact that if a corrosive liquid be mixed
with a salt, or with a metal opposed to it, in a place
almost destitute of air, though the two when mixed
together effervesce in a conspicuous manner, yet the
heat produced by them does not seem to be so intense
as it would otherwise be — a fact which has been
noted also by the illustrious Boyle.

I made also an experiment in an exactly similar way
to ascertain whether fixed salts mixed with acid
liquids and other actions of that kind diminish the
elastic force of the air, and found as the result of
observation that, if the elasticity of the air is to be
manifestly diminished, it is absolutely necessary that
the action should be of such a kind that the exhala-
tions of the fermentation should last for some time
and be disseminated through the air, or at least, that
the exhalations if suddenly produced should undergo
great condensation afterwards. For it is to be noted
that the air in the aforesaid glass is impaired by the
fumes dispersed through it even after the iron has been
taken out of the spirit of nitre and the fermentation in
the vessel has ceased. For otherwise if the air had
.been injuriously affected only while the action lasted,

lOO Mayow

then the space left by the impaired air would have been
filled by the vapours emitted, and consequently the
water would not have risen in the glass except in sO'
far as these underwent condensation. But the water
rose in the glass much faster than vapours of that
kind usually condense, so that we must believe that it
ascended not only into the place of the condensed
vapours but also into that of the air at that time
impaired. Indeed we must suppose that particles of
the liquid and of the metal, dispersed through the air
and fermenting there, gradually rub its particles and
diminish their elastic force. Hence if the vapours
produced by any action are of such a sort as cannot
last a good while in the air, the water will only ascend
into the space left by them on their contraction by
condensation. If therefore they are of such a kind
that they do not undergo notable condensation, the
water in the said glass will not rise above the limit
first marked. Whenever, I say, the vapours generated
will occupy more space than is left by the impaired air,,
then, however much the elastic force of the air is
diminished, it will not be observed in the said glass.
And hence it is that if action is caused in the glass by
spirit of nitre and a fixed salt being mixed, as also by oil
of vitriol and iron acting on each other, in the manner
aforesaid, the water will not rise above its original level.
It is to be noticed in passing that although the
exhalation produced by the spirit of nitre and iron^
when acting on one another, will never pass into a
liquid condition, as will be shown below, still it can
scarcely be thought that it is really air. For when the
fermentation was first produced in the aforesaid glass,,
the air in it was for the most part impaired — at least
as regards elastic force — as was previously pointed out ;
yet when the glass was almost filled with the exhala-

On Sal Nitrum and Nitro- Aerial Spirit lOi

tioii produced by the fumes, instead of with air, then the
water did not rise in the glass after the second action
as it did before, because that exhalation could not,
like air, be diminished as to its volume by the ferment-
ing particles, but was on the contrary increased by
them. But this sort of exhalation will be discussed
more fully later.

After this experiment we must suppose that air
when breathed by animals loses its elastic force in the
following manner. For I assume, in the first place,
that the mass of the blood is a liquid conspicuously in
a state of fermentation, as will be shown below. Since
then through the action of the lungs aerial particles
are mixed intimately and in the minutest parts with
its fermenting particles, it comes to pass that the aerial
particles have their elastic force diminished by the
particles of the blood in the same way as by the
vapours of fermentation in the aforesaid glass. Indeed
it is probable that the fermenting particles of the blood
rub the aerial particles interspersed among them and
strike out from them the nitro-aerial spirits, and that
at last the aerial particles, deprived of their nitro-aerial
and elastic particles, become unfit for sustaining life
and lose besides a part of their elasticity.

Now that we have introduced nitro-aerial particles
into the mass of the blood, the question at once
follows what use they serve. I discussed this subject
in my treatise on Respiration published a good while
ago. Let me be permitted, however, to add some
things here. It is our opinion, then, that as in
vegetables so also in animals, nitro-aerial particles are
the principal instrument of life and motion.

For in the first place nitro-aerial spirit when mixed
with the saline-sulphureous particles of the blood
appears to excite in it vital fermentation. In fact, just

102 Mayow

as nitro-aerial particles when they slowly enter the
pores of the earth encounter there saline-sulphureous
particles, immature indeed, in an obscure fermentation
on which, as has been shown elsewhere, the life of
plants depends ; so the same nitro-aerial particles
when introduced more profusely into the mass of the
blood b}^ the action of the lungs, and mixed in their
minutest parts with its saline-sulphureous particles,,
brought to a state of active vigour, produce a very
marked fermentation such as is requisite for animal
life. For it is to be noted that blood consists of
the same. particles as earth but in a more exalted state.
For as immature sulphur, when closely combined with
the seeds of a fixed salt, composes earthy matter, as has^
been said elsewhere, ^o the mass of the blood is
made up of saline-sulphureous particles raised to a
suitable volatility, and hence it is that both have
the same colour — to wit, a dark purple. Indeed I
attempted to show above that nearly all fermentations
of natural things result from the motion of nitro-aerial
particles ; and in fact I have no doubt at all that the
effervescence of the blood is due to the same cause :
accordingly when respiration is arrested, the effer-
vescence of the blood immediately ceases and animal
life is extinguished.

And what confirms still more the view just stated is.
the fact that the blood which entered the lungs with,
a dark colour, returns from them m.ore florid and
ruddy, as arterial blood is, as was observed by the:
illustrious Lower in vivisections. He also showed
that that change made in the mass of the blood is
caused, not so much by its being triturated in the
lungs as by the air being mixed with it. For when
venous blood is placed in a vessel, the upper surface
which is exposed to the air acquires a scarlet and

On Sal Nifruin and Nitro-A'a'ial Spirit 103

florid colour, although the blood at the bottom of the
vessel appears as a dark purple ; and yet it too if
exposed to the air will after a short time become
ruddy. So that it is not surprising that the blood in
the lungs, where the air diffused through all its
particles mixes intimately with it, is rendered florid
throughout.

And now we remark that air mixed with blood
produces the ruddy colour in it, since it sets up
fermentation in its mass. For arterial blood which is
florid has its particles in motion and also effervesces
conspicuously, while the darker and duskier venous
blood is more grumous and is more quickly coagulated
on account of its feebler effervescence.

The following experiment also corroborates the
view here taken. If blood that has been kept for
some time in a vessel be put into a glass from which
the air is exhausted by an air-pump, the blood at the
surface where it was of a florid colour will effervesce
gently and rise in bubbles. But if arterial blood
while still warm be put in a place void of air, it will
expand in a remarkable way and rise in an almost
infinite number of bubbles. And it is probable that
this results partly from the effervescence of its particles
and their being thrown into movement, and partly
from its particles being mixed with air.

But to submit yet another experiment. If spirit of
nitre be poured upon a liquid saturated with volatile
salt and sulphur, such as the spirit of hartshorn
impregnated with its own oil, a very marked effer-
vescence and a very ruddy scarlet colour will be pro-
duced at once in the liquid, and yet this florid colour
changes into a dark purple when the liquid ceases to
effervesce. No doubt the nitro-aerial particles (and
we have elsewhere shown that the spirit of nitre

I04 Mayow

abounds with them) effervescing with the saline-
sulphureous particles of the aforesaid liquid seem to
cause the scarlet colour which rivals that of arterial
blood. For it is the nature of nitro-aerial particles
when set in motion to produce a ruddy colour in the
substances in which they are, as happens in spirit of
nitre, which is ruddy during distillation.

It is to be noted here that as nitro-aerial particles
cause the fermentation of the blood, so this fermenta-
tion strikes out, in the way shown above, and draws
from the air other nitro-aerial particles by which fer-
mentation goes on anew in the blood. In fact nitro-
aerial spirits, when mixed with the mass of the blood
in the lungs, produce an intense enough effervescence
in it ; but they are soon separated for the most part
from the blood in the system of the body, for purposes
to be explained below ; so that the fermentation of
the blood on its return to the lungs is for want of
them much diminished and more sluggish ; but still
it does not • cease so completely as to be unable to
draw nitro-aerial particles from the air for its renewal.
And so in fine the movement of fermentation is per-
petuated in the animal Automaton.

Just as the fermentation of the blood, so also its
heat arises I think from the effervescence of nitro-aerial
particles with the saline-sulphureous particles of the
blood. For if any saline-sulphureous minerals, such
as the vitriolic Marchasites and the like, be exposed,
when recently dug up, to moist air, they will shortly
effervesce and become intensely hot, inasmuch as
aerial particles give rise to a very pronounced efferves-
cence when they meet with the saline-sulphureous
particles of the mineral. Further all substances, at
least those which are endowed with some degree of con-
sistency, grow somewhat warm while fermenting — a

071 Sal Nitriim and Nitro-Aerial Spirit 105

result which is due as I have tried to show elsewhere
to the motion of nitro-aerial particles. How much
greater then will be the effervescence and heat of the
blood which abounds in saline-sulphureous particles
duly exalted, and with which aerial particles are densely
and in their minutest parts mixed by the action of the
lungs ? To this I add that the very intense heat which
animals experience when urged to violent motion, arises
partly because in violent movements there is very
great need of increased respiration, and thus the nitro-
aerial particles introduced into the blood in greater
abundance will produce greater effervescence and heat
than usual ; for the friction of the limbs in the most
violent movements is not so great as to be able to ex-
cite so fervid a heat. Nay, if any one breathes, even
when at rest, but a little more intensely, he will soon
feel himself in an unusual glow of warmth. However
the heat excited in animals by violent exercise is in
part also due to the effervescence of nitro-aerial particles
and sulphureous particles, originating in the motor
parts, as will be pointed out elsewhere.

I am not unaware that the learned Dr Willis in his
treatise on the Heat of the Blood has advanced various
arguments by which he endeavours to show that
the heat of blood is not due to its fermentation.
Ihis eminent man also asserts that liquids never
acquire heat in fermenting. But indeed it is evident
from common experience that all the thicker and
richer liquors, those namely which abound in saline-
sulphureous particles, such as strong ale and the
like, grow somewhat warm in the course of fermenta-
tion. However there is no kinship between any other
liquids and the mass of the blood, since the latter is so
thick that its particles do not exist in a fluid state
-except when fermenting. Hence blood when drawn

io6 Mayow

off is soon coagulated and acquires a certain consist-
ence. But such things as are possessed of consistence,
even in the opinion of this learned man, generate heat
in effervescing. Further, blood abounds beyond all
other liquids in saline-sulphureous particles, and nitro-
aerial spirits are densely and most minutely mixed
with them, and when these effervesce together, as it is
their nature to do, an intense enough heat must arise ;
while in other liquids, fermentation is only produced
by a much more minute quantity of nitro-aerial and
saline-sulphureous particles. Further, the nitro-aerial
spirit by which fermentation is excited in other liquids
is not supplied directly from the air with motion
and vigour but is innate in these liquids themselves,
wrapt in the embrace of the salt and fixed, as has been
shown elsewhere.

But yet another difficulty brought forward by this
eminent man opposes what has been said — viz., that the
action and heat of contrary salts effewescing together
ai'e increased in a vactmni^ as is proved by Boyle's
experiments. Wherefore^ if the heat of the blood were
caused by its fermentation^ it ivould seem that it ought
to become more intense when the air is withdrawn. But
on the contrary^ if by suppressing respiration air is pre-
vented from entering the bloody fermentation soon ceases
and the animal quickly dies.

I reply that from the fact that the fermentation of
the blood immediately ceases on account of want of
air, it follows that it is caused by nitro-aerial spirit, as-
has just been said.

Further, although contrary salts when mixed to-
gether, and other things of a like kind when ferment-
ing, expand and rise more in a place void of air than
elsewhere, still it is by no means on that account to
be granted that they effervesce more intensely. For

On Sal NitriLtn and Nitro- Aerial Spirit 107

the particles of any substance when effervescing in un-
confined air are so much pressed by the weight and
pressure of the incumbent atmosphere that they can-
not expand freely ; while yet the same particles, being
scarcely burdened at all in a place void of air, will in
performing their movements spread out and swell up
much more : but this does not come from their more
intense action and motion, but from the removal of
the hindrance. And hence it is that if water slightly
warmed be put in a place void of air, its more agile
particles will make the liquid swell and as it were boil,
and yet it is not to be supposed that these particles
are agitated with a greater force than before. So that
clearly, even if the fermentation of a mixture of con-
trary liquids in a vacuum were to go on with less force
than in free air, still their fermenting particles would
spread out to a greater extent than otherwise owing
to the withdrawal of the pressure of the atmosphere.

To this I add that contrary salts, if mixed together
in a vacuum and then quickly removed after effer-
vescence has gone on for some time, do not appear to
have been heated as much as in other circumstances.
So that it would appear that even the heat of contrary
salts fermenting together, depends to some extent on
nitro-aerial particles struck out from the air, as we
have already hinted.

It is besides to be noted that there is a great
difference between the fermentation of the blood and
that of contrary salts, inasmuch as the effervescence of
the latter is due to an internal principle, namely to
nitro-aerial particles contained in them, as I already
endeavoured to show, while the fermentation of the
blood is excited by the nitro-aerial spirit supplied by the
air meeting its saline-sulphureous particles. Whence
it is, that the access of air is not so necessary for the

io8 Mayow

action of contrary salts. But such things as have not
nitro-aerial particles contained in them, such as the
mass of the blood, all saline-sulphureous minerals, and
likewise such things as ferment from extraneous
moisture and heat, effervesce only when nitro-aerial
particles reach them from the air. And this is the
reason why the fermentation of the blood subsides im-
mediately when the air is withdrawn.

But the reason why blood quickly coagulates when
drawn off, although exposed to the air, is because it is
necessary for the fermentation, and therefore also for
the preservation of the fluidity of the blood, that nitro-
aerial particles should be mixed densely and in very
minute parts with its saline-sulphureous particles, as
takes place in the lungs. And yet even blood that
has been shed effervesces at its surface, that is, where
it is mixed with the air, as was previously shown.

From what has been already said, it is I think in
some degree made out that the fermentation of the
blood, and hence also its heat, arises from nitro-
aerial particles fermenting with its saline-sulphureous
particles ; so that we do not need to have recourse to
an imaginary Vital Flame that by its continual burn-
ing warms the mass of the blood, much less to affirm
a degree of heat in the blood intense enough to produce
light, from the rays of which, transmitted to the brain,
the Sensitive Soul is supposed to be produced. I
know not what the ancients dreamed about certain
feral fires hidden in the urns of the dead, but now
for the first time the vital flame, if such a thing can
be, is kindled in the viscera of animals, so that we all
now burn like Ucalegon, and there is no reason why
we should any longer wonder at a Salamander living
in the midst of flames. But really fire seems to be
better adapted for the dissolution and destruction of

On Sal Nitriim and Nitro- Aerial Spirit 109

things than for sustaining animal Hfe. Nor indeed
is the mass of the blood in any way suitable for pro-
ducing flame ; for although it consists of sulphureous
particles, yet these are held so firmly in the embrace
of the saline ones that blood will not burn, even when
thrown into the fire. But if any fire of this sort were
kindled in the mass of the blood when the blood
rushes forth from a divided artery, the flame would
certainly reveal itself by its own light. For it is not
to be thought that any flame is ever kindled which is
not luminous and also somewhat caustic and destruc-
tive, unless one is disposed to palm off fumes for
flame. Nor is it credible that the vital flame is
extinguished in the blood as it rushes out of the
vessels, for the air by blowing on it is fitted rather to
excite than to extinguish fire. And lastly, what are
we to think of the vital fire of aquatic animals ? It
must indeed be fierce and invincible to burn under
water and be such as the whole ocean cannot quench.
The existence of subterranean fires is not yet estab-
lished ; it is much less probable that there are sub-
aqueous fires. With respect to a lucid soul inhabiting
the brains of animals, I ask how it is possible that this
light which is supposed to enlighten with its rays the
whole brain and nervous system, should never be seen
by the eye. Truly, fires of this sort and new lights,
no less in Anatomy than in Religion, have always
seemed to me vain and fanatical.

With respect to the fermentation of the blood we
note further, that if the saline-sulphureous particles
in the mass of the blood have been too much elevated,
the nitro-aerial particles mixed with them will give
rise to a very impetuous effervescence and to febrile
heat. And thus it is that an ulcer of the lungs pro-
duces a hectic fever ; for the nitro-aerial particles,

110 Mayow

mixed with the too highly exalted saline-sulphureous
particles of purulent matter, excite a very intense
eifervescence and febrile heat.

When saline-sulphureous and nitro-aerial particles
effervesce so much in long-continued fevers, it comes
about that the volatile salts of the blood are so worn
that they change at last, in the manner already
described, into acid salts. And hence it is that the
blood acquires an acid nature after long-continued
fevers ; indeed the case is not very different from
that of strong ale, which after long fermentation is
converted into vinegar. Nay, even when the fer-
mentation of the blood goes on aright, its saline
particles are in course of time sharpened and liquefied
by the action of the i nitro-aerial spirit, and in
combination with other (volatile) salts constitute a
certain acido-saline salt not very unlike Sal-Armoniac.
And thus it is that urine is impregnated with a certain
Sal-Armoniac, and the proof of this is that copper
is corroded by urine in the same way as by Sal-
Armoniac. Further, a solution of sulphur made in
lye is precipitated by urine poured on it just as by
any acid liquid. Hence if ashes have urine or even
blood mixed with them, volatile salt will in distillation
be abundantly derived from them, inasmuch as the
fixed salt of the ashes absorbs whatever of acid there
is in the urine, so that its volatile salt, freed from the
acid salt, readily ascends, precisely as happens in dis-
tilling Sal-Armoniac mixed with fixed salt.

Besides the uses thus far assigned to nitro-aerial
spirit, a very great many other offices are served by it.
For when nitro-aerial particles effervesce with the
mass of the blood in the manner aforesaid, its saline-
sulphureous particles are brought to due volatility,
just as the sulphureous particles from terrestrial matter

071 Sal Nitrum and Nitro- Aerial Spirit iii

are brought to due maturity by the aid of nitro-aerial
spirit, as has been shown elsewhere.

Further, in all the internal movements which take
place in the bodies of animals, as in the digestion of
food, and also in that most intense effervescence which
gives rise to muscular contraction, nitro-aerial particles
play the chief part, as I shall attempt to show in the
fourth treatise.

I

CHAPTER IX

WHETHER AIR CAN BE GENERATED ANEW

Now that we have shown above in how many ways
air is impaired, it will not be out of place to inquire
whether it can be generated anew. On this point I
shall introduce an experiment not very unlike the
one by the illustrious Boyle already referred to.

Let, then, spirit of nitre and spring water, mixed in
equal quantities, be placed in a glass vessel of sufficient
size. Then let a small glass be so placed under the
mixture that it shall be completely filled with the
liquid. This done, let two or three globules of iron
be placed at the mouth of this glass, and let it lie
inverted at the bottom of the other, as is shown in
Plate v.. Fig. 3, care being taken that these globules
do not fall out of the glass, and to secure this let the
mouth of this glass be closed with the finger or in any
other way, until it rests at the bottom of the other
glass. These preparations made, the acid menstruum
will, after a short time, corrode the iron globules and
effervesce conspicuously with them, and the exhala-

1 12 Mayow

tions caused by the effervescence will rise in the
form of bubbles to the top of the glass and constitute
the air there, which, gradually increasing, will de-
press the underlying water. Let the glass, when it
is completely filled with air of this kind, be raised a
little, that the iron globules, which are to be removed
from the liquid, may escape from it, care however
being taken that the mouth of the glass be not raised
above the liquid. And so we shall see that air which
occupied the whole glass, gradually condense, and the
underlying liquid rise into its place. And yet this
air will not all become liquid, for the glass will be
always about one-fourth filled with it ; and this air,
however long kept, even in the coldest weather, will
never be condensed intQ a liquid. If the iron globules
be placed under the mouth of the glass while it is still
inverted and put a second time into it, air will be
produced anew, a certain part of which will never
become liquid. So that the glass will be about half-
filled with exhalations that will never be condensed.

If oil of vitriol mixed with water be substituted
for spirit of nitre, or if a very sluggish fermentation
be excited in the manner described, or also if the
iron globules be allowed to remain in the glass for a
day or two, then the air generated in this way will
scarcely suffer condensation at all. For the partial
contraction of the air in the aforesaid glass was due
to this, that the exhalations produced by violent
fermentation were agitated with a very rapid motion,
which, gradually abating, the air was reduced to
smaller bulk ; while, if the fermentation has been
mild and has gone on for a long time, the exhalations
generated later will take up and fill the place left by
those previously condensed, so that the air will
scarcely suffer any condensation at all.

Oji Sal Nitrtim and Nitro- Aerial Spirit 113

It is not easy to know whether air of this kind is
really common air or not, but this is certain, that it
will expand like air upon the application of a gentle
iheat, and when cooled again will contract. Nay, this
:air is endowed with elastic force no less than common
air, as I ascertained by the following experiment.

Let a small glass tube of the diameter of a goose
quill and about four inches long, be hermetically
sealed (as chemists say) at one end ; then let a single
drop of water be dropped in iby the other and open
end, and let it be marked on a paper attached to the
outside of the glass how much of the space of the
glass the drop occupies ; then let a second drop, and
then others be dropped into the glass in the same
way as the first, and let the space occupied by them
b)e marked on the aforesaid paper. This done, let the
•open end of the glass be fitted into the narrower
opening of another glass open at both ends, and then
let that opening be carefully closed with suitable
•cement, as is shown in Plate V., Fig. 5. Let the glass,
when prepared in this manner, be so submerged in
water contained in a suitable vessel that, when its
orifice is turned upwards, all the air may pass out and
water enter in its place, great care being taken that
the narrow glass be also filled with water. Then let
the glass filled with water be inverted and let it rest
on the bottom of the other vessel, and let things
remain in this condition.

And now the aforesaid air is to be transferred to
this glass in the following manner. Let a small dish,
big enough however to receive the mouth of the
vessel containing the air, be placed under that vessel.
Next let the small dish filled with the aforesaid Hquid,
together with the inverted glass, containing the air,
resting upon it, be transferred to the vessel in which

H

1;I4 Mayow

the glass first described has been placed. And let the-
orifice of the glass in which the air is, be placed in
the orifice of the other glass filled with water, as is
seen in Plate V., Fig. 5 (care being taken that the
mouth of neither of the glasses is raised above the
surface of the water), and let the glass be inclined
until the air contained in it escapes and ascends into
the other glass, which can in this way be filled with
that air, although it is enough that a little of the air
be introduced into it.

And now the glass into which the air is transferred
in this manner, is to be enclosed in another glass from
which the air may afterwards be pumped by Boyle's,
air-pump, which may be done in this way. Let a
vessel, not too large, but capable of admitting the
orifice of the glass in which the air has now been
collected, be put under it, and then let this vessel
filled with water be removed, with the other glass
inverted and resting upon it, and be put inside the glass,
from which the air is to be pumped out. After the
air has been partly exhausted, the air enclosed in the
said glass will expand beyond the cavity of the glass,
and most of it will escape through the underlying
water. When the air has been removed as far as
possible by the pump, let it be permitted to enter
anew. When this is done the water in contact with
the glass in which the aforesaid air is, will be driven
up into it on account of the pressure of the atmo-
sphere and will almost entirely fill it. For the air
which was left in that glass will occupy only a part
of the narrower glass ; and yet that small portion of
air, a moment ago, when the pressure of the sur-
rounding air was almost withdrawn, occupied the
whole glass, and was able to resist the pressure of the
surrounding water, and also of the air which could

On Sal Niiruni and Nitro- Aerial Spirit 115

not be all pumped out. Therefore if the volume of
the whole glass be measured by means of water put
into it drop by drop, and compared with the space in
the narrower glass which the residual air had filled^
the extent to which the said air had expanded will be
ascertained. For by as much as the one space exceeds
the other, so much was the expansion of that air.
And from many repetitions of the experiment, I have
ascertained that air of that kind expands to more
than two hundred times its volume ; and indeed if it
had been relieved from the pressure of the surround-
ing water, it would have expanded about twice as
much. Nor will common air, when treated in the
same manner, expand more ; but it must be observed
that in making experiments of this kind, every pre-
caution must be taken that the airs, whose elastic
powers are to be compared with one another, are
pressed by an equal weight of the surrounding water,
and also that the pressure of the surrounding air be
diminished to an equal extent in every experiment,
by pumping.

I note here in passing that I made an experiment
in a similar way, to find whether the air in which an
animal or a lamp had expired, possessed elastic force
in an equal degree with unimpaired air, and, in fact, it
appears to me to expand no less than any other air, as
was previously said. But in order that experiments
of this kind may be made, it is sometimes necessary
that the air whose elastic force is to be investigated
should be drawn off from the glass which contains it,
and transferred to the glass first described, and this
can be done in the following manner. Let a glass,
not too large, be submerged in the water in which
the glass is which contains the air to be drawn off, so
that it is filled with water ; then let this glass be

ii6 Mayow

inverted and placed under the orifice of the other
glass, and raised in it in the following manner.
A transverse rod has to be attached, from the first, to
the inner sides of the glass, as is seen in Plate V.,
Fig. 4. And let a string be so suspended from the
rod that both its ends, drawn from under the ori-
fice of the glass, hang outside. Then one end of
the string is to be tied to the bottom of the glass that
is to be raised, and the other end pulled till the glass
rises above the surface of the water inside. When the
water has fallen out of the glass which has thus been
pulled up in an inverted position, and air has taken its
place, let this glass be pulled down by means of an-
other string previously fastened to its mouth, and taken
out of the other glass^ in such a way that its mouth
may remain continuously inverted ; and then, lastly,
the air contained in it may be transferred to the glass
first described, in the manner already shown.

Although air generated from the aforesaid fermen-
tation possesses no less elastic force than common air,
it does not on that account follow that it is really air
— viz., such as possesses vital and igneous particles.
For that air in which an animal or a light has expired
possesses elastic force in an equal degree with inviolate
air, and yet it is destitute of nitro-aerial and vital
particles. But in order to determine whether this air
generated anew is fit for sustaining life or not, let the
following experiment be performed. But before this
can be done, it is first of all necessary that air of that
sort be generated in suflBcient abundance, which can
be done as follows without any great waste of the
aforesaid liquid. Let a sufficiently large glass be im-
mersed in water and filled with it, and let it remain
inverted. And now let the air generated in a small
glass, in the manner described, be transferred to this

On Sal Nitrum and Nitro- Aerial Spirit 117

glass, as was shown above ; then let another small
portion of the air produced as before be conveyed in
like manner to the glass, and let this process be repeated
until the air is present in sufficient quantity.

And that we may now make our experiment, let a
small animal, say a mouse placed in a small cage, be
placed in the upper part of the cavity of an inverted glass
with a suitable support below it, as is delineated in Plate
v.. Fig. 6. And let the glass with the animal inside be
so immersed in the water, that the water inside may
rise as high as the support on which the mouse rests,
which can be done by means of the curved syphon de-
scribed in Chapter VII. ; and let everything remain in
this condition till the animal dies, and let the length
of time during which the animal breathes in the glass
be carefully noted. Now let the dead animal be re-
moved and another living animal be put in its place.
And let it as before be shut in the glass immersed in
the water, care being taken that the same quantity of
air as before may be enclosed in the glass. This done,
let the aforesaid air be transferred, as described, into
the glass containing the animal, in such quantity that
the air thus introduced shall by two or even three times
exceed the quantity of ordinary air enclosed from the
first in the glass. And then let the glass be raised till
the water (which is depressed by the air introduced)
reaches the support on which the animal rests, care
being taken that the mouth of the glass be not lifted
above the water. And let everything continue thus
till the animal dies. When this has occurred we shall
find that the animal has not lived much longer in the
glass on the second occasion than the other did on the
first ; that is to say, before the aforesaid air was intro-
duced into the glass. But if that air were truly
air suitable for sustaining life, the animal put in on

Ii8 Mayow

the second occasion would have survived twice as long
as the previous one. And the reason that the animal,
when the said air was put into the glass with it, lived
a little longer than it would otherwise have done,
appears to be that the air enclosed in the glass could
be more gradually and less copiously breathed and cor-
rupted by the animal in consequence of the admixed
air.

Here, too, we might repeat our remarks in the
previous chapter on the difference between this sort
of air and common air. And yet it is probable that
there is a great likeness between air of this kind and
common air, and that the elastic force of both is due
to no very diff*erent cause. For since iron consists of
rigid particles, and the corrosive spirits consist of very
elastic nitro-aerial particles, as has been elsewhere said,
the air produced by their fermenting together will not
be very different from common air, inasmuch as the
latter appears to be formed of rigid particles, and these
imbued with nitro-aerial spirit, as I have elsewhere
endeavoured to show.

CHAPTER X

HO W FIRE IS PRO PA GA TED. ALSO WHY FLAME
RISES TO A POINT

In the preceding chapters the nature of fire has been
frequently discussed ; let us now inquire how it is that
fire, so very small when first kindled, spreads itself
so enormously if only it be supplied with sufficient
abundance of sulphureous nutriment. For it is to be
noted that nitro-aerial and sulphureous particles, when

On Sal Nitrinn and Nitro- Aerial Spirit 119

in fiery motion, agitate with their own velocity very
many others, and these in their turn others of the
same mass ; so that indeed the smallest spark is
sufficient to cause a wide conflagration, which, yet, is
entirely contrary to the ordinary laws of nature. For in
other cases when one body in motion impels and moves
another at rest, the motion in both is diminished.
For a moving body which strikes another body and
moves it from its place, loses as much of its own
motion as it communicates to the other ; so that
when a few particles set in motion a large number of
the same mass, the motion in each will be greatly
•diminished.

That the burning particles in fire, then, should in-
-crease their motions to such an extent, it seems to me
necessary that some other moving body should be
added to the ignited particles, to promote and intensify
their motion. And I think this is how it occurs. It
is no doubt probable that sulphureous particles when
divided most minutely, and violently agitated by the
application of fire or in any other way, impinge upon
the nitro-aerial particles residing in the particles of the
air, or of common nitre, and drive them into those
small spaces in which the subtle matter revolves with
swiftest motion (as we showed above), but that the
nitro-aerial and sulphureous particles, when driven
within the spherules which are described by that re-
volving matter, are driven further and forced out by it
with their motions greatly increased, and that at last
the nitro-aerial particles, on being violently sundered
in this way from the fixed salt of nitre, or from the
aerial particles with which they were previously most
firmly united, are thrown into a truly fiery motion.
Assuredly we must suppose that the sulphureous and
nitro-aerial particles, and also the subtle matter, are

120 Mayoiv

fashioned by the supreme Artificer with truly mar^
vellous skill, so as to be naturally adapted for throw-
ing each other into a motion of extreme velocity.
Indeed, not only in the burning of fire but in produc-
ing most natural movements, we must assume as
much skill and careful fitting of the mutually adapted
particles, as in automata constructed with the most
accurate human art. If any one should think that in
explaining spontaneous movements of this kind I am
having recourse to things too minute, I reply that it
is nature's way to produce all the greatest things by
means of the least, for how small and delicate are
those spirituous particles which set the huge machinery
of the elephant in truly stupendous motion ? And
what is to be said of the very small particles of
insects ? For as their whole bulk is merely a point in
appearance, how minute must those portions be which
we cannot suppose to be one-thousandth part of the
whole ? Indeed I make bold to affirm that natural
movements of this kind are effected by particles too-
minute for human discernment.

It is to be concluded from the foregoing that the
ignited particles in the burning of fire are agitated
with elastic impulse, for just as we have shown above
that the power of recoil in bent rigid bodies is due to
the pulsation of subtle matter, so also we maintain that
the motion of ignited particles results from impact of
the same matter. Indeed the burning of fire does not
seem to be very different from the bending to fracture
of any rigid body, or rather of the aforementioned
glass drops. For as in bent rigid bodies, their particles^
thrust within the circles of the subtle matter, are
struck by it, and at last, if the rigid body is bent to
breaking, are violently driven out, so in fire the
sulphureous and nitro-aerial particles, when they enter

On Sal Nitrum and Nitro- Aerial Spirit 12 r

the minute pores of the air or of nitre itself, and are
impelled there into the spherules of the subtle matter,,
produce the same effect in the aerial particles, or on
anything else impregnated with nitro-aerial particles,,
as if, like rigid bodies, they were bent to breaking : so
that the igneo-nitrous particles would appear to burst
forth with elastic impetus from the air, not otherwise
than the small bits of glass from the fractured glass.
It is a corroboration of this view that aerial particles-
and the particles of nitre itself, in which, namely, igneo-
nitrous spirit especially resides, become stiff like rigid
bodies and are imbued with elasticity, and are con-
sequently of a sort fit for having igneous particles shot
out of them with elastic impetus.

It would be easy to show here that nearly all natural
movements, such as the generation and dissolution
of things and the internal motions of opposed liquids,
are, similarly, to some extent due to the battering of
the subtle matter. It is probable indeed that these
motions are excited in the same way as fire is kindled ;
for fire appears to be nothing but the most intense
fermentation of nitro-aerial and sulphureous particles.
It certainly does not seem to be suflficient to say with
the eminent Willis in regard to these natural motions,,
that the more active particles expand, ascend, and
finally fly away ; for, in a discussion of this sort, what
should specially be shown is why particles at rest
begin to move, for whatever is at rest will remain
for ever at rest, if it is not set in motion by some
cause. With respect to motion of this kind, it appears
to me necessary to suppose some perpetually moving
matter by the impulse of which these motions are
effected. As then the very rapid motion of fiery par-
ticles seems to proceed from this, that the sulphureous
particles coming up to the particles of nitre or of air

122 Mayow

and there impinging upon the subtle matter agitated
with extreme velocity, are, by its impulse, thrust out
with elastic violence along with the nitro-aerial par-
ticles which these substances contain ; so the milder
fermentation of natural things must be supposed to
arise from this, that nitro-aerial particles, along with ex-
traneous moisture, penetrate a saline-sulphureous mass
and enter the abode of the subtle matter, by which, as
it is in violent agitation, the nitro-aerial together with
the sulphureous particles are driven off. For fiery
effervescence seems to differ only in this respect
from the milder internal motions by which plants
hasten to growth or decay, that in fire, nitro-aerial
particles, in close union wdth fixed salt or with aerial
particles, are, by the impulse of sulphureous particles
and of the subtle matter, violently sundered from their
partner and thrown into very brisk motion ; whereas,
on the other hand, in the said fermentations, as the
sulphureous particles are not held so firmly in the
•embrace of fixed salt, they are thrown into a milder
motion by the impact of the nitro-aerial particles and
of the subtle matter. But these matters have been
more fully discussed elsewhere. Nor does the process
seem to be different in the effervescence of opposed
liquids, for when one of these intrudes into the pores
of another, and therefore also into the abode of the
subtle matter, and is expelled again, an internal move-
ment and effervescence of the particles is set up.

WHY THE FORM OF FLAME IS ALWAYS
POINTED

As to fire, let us consider lastly why flame of every
-sort rises to a point. On this it is to be remarked,
in the first place, that the sulphureous particles, burst-
ing out from the burning matter, pass through the

On Sal Nitrnm and Nitro- Aerial Spirit 123

•whole blaze and kindle flame everywhere in their
passage. For since the sulphureous particles, which
burn at the top of a lamp, have proceeded from the
wick, they must necessarily have passed through the
whole of the intermediate flame. Further, it is not to
be doubted that these particles were burning from their
first entrance into the flame, since the lowest part of
the flame is produced only by the kindling of sul-
iphureous particles. And hence it is that when a lamp
goes out in consequence of a failure of sulphureous
nutriment, the flame is last seen at the top and at
•some distance from the wick. For it is the last group
of sulphureous particles passing through the blaze, and
-everywhere in its transit kindling flame, that is seen at
the top of the blaze. But since no sulphureous par-
ticles now remain to follow these last ones, there must
be an interval without flame between the last burning
particles at the top of the flarne and the wick.

But now the question arises why the sulphureous
particles at a certain distance from the wick no longer
kindle flame. For since the sulphureous particles burn
at the extreme verge of the flame, they must conse-
quently be in more violent motion there than when,
as yet unkindled, they were about to enter the flame.
And therefore there seems to be more reason for these
particles, once kindled, persevering in their fiery
movement and flame, than for their entering upon a
fiery movement at first. As to this, my opinion is
that the fire is extinguished at a certain distance
from the wick, not because the motion of the sul-
phureous particles is diminished, but because, in their
passage through the flame, they are rubbed so much
and made so small and subtle by their own combus-
tion that they become at last incapable of throwing
nitro-aerial particles into fiery movement. In fact,

124 Mayow

for the formation of a flame, it seems to be necessary
that the sulphureous particles should neither be too
fixed nor very volatile. For we notice that the sul-
phureous particles of spirit of wine and also the very
subtle particles of camphor, are scarcely able to throw
nitro-aerial particles into fiery motion. And this is
the reason that the fire they make is but languid and
almost harmless. And indeed it is probable that
sulphureous particles, in passing through the flame,,
are rendered so subtle by their own burning that
they become quite unfit to produce fire. And this
seems to be confirmed by the fact that if any polished
plate be placed in the flame of a lighted candle, we
shall soon see it covered with soot ; but if the plate
be held a little above th^ flame, no soot will gather on
it. For the soot adhering to the plate seems to be
nothing else than the sulphureous particles which
shortly before were burning ; now indeed they are
changed somewhat in consequence of their burning
and rendered more subtle and scorched. But those sul-
phureous particles which have burned longer, become
at last so fine that they are incapable either of con-
stituting the grosser structure of soot or of producing
flame. It is a confirmation of this that the lower
part of any flame is very different from the top. For
the lower part is usually blue, while the upper part
burns more brightly. And this difference seems to
result from the different state of the sulphureous
particles. Now then, since the sulphureous particles
carried through the flame get smaller during the
whole course of their passage and are therefore to
some extent consumed, the flame must gradually
become smaller and end at last, as it does, in a
point.

On Sal Nitrum and Nitro- Aerial Spirit 125

CHAPTER XI

OF THE AERIAL VORTEX, OR ASCENT OF SEA-
WATER. Anglice: A SPOUT

Seeing that we have treated of the elastic power of air
and of its motion, let me be permitted to submit here
some observations regarding the wonderful pheno-
menon familiar to sailors, which is in English called
a Spout ; that, namely, in which a huge mass of water
rises up on high like a pillar, and besides a whirlpool
of water is carried aloft. For I think that that pheno-
menon is caused by a whirling movement of the air
and by a diminution of its elastic force and pressure.
For I cannot agree with those who maintain that an
ascent of water such as this, arises solely from the
circumgyration of the water, as though on being
driven into a circle, whether by winds rushing from
opposite points or in any other way, it were thrust
on high at the centre of its vortex. For it is scarcely
credible that from this cause water could be raised to
so great a height as in the aforementioned pheno-
menon, since there is nothing to hinder water raised
above the surface in that manner from soon flowing
over to the sides. But indeed it has been ascertained
by experiment that water, when made to rotate, rather
falls downwards at the middle of its vortex than
ascends in that way.

But in order that the reason of the phenomenon
may be known, I have thought it desirable to present
a representation of it, as it was delineated by a clever
sailor who had much experience of these things,
in Plate VI., Fig. i. In this figure:

126 Mayow

a, a^ is the huge mass of sea-water rising up like a
pillar or a mountain. This mass is sometimes of
greiater, sometimes of less height, and assumes some-
times a pyramidal and occasionally an orbicular form.

c^ c, is a somewhat dense fog produced by the
ascent of fine water particles. This, which derives
its origin from the aforementioned mass of water^
expands in all directions, but it soon begins to con-
tract gradually, and at last ends in a point at e, e.

e^ e^ /,/, is a gloomy tube which, descending from
an overhanging cloud, directly overtops the afore-
said column of water. This tube is at first like a
stream of smoke, which seems to descend gradually,,
yet so as to leave a gap between its lower end and the
underlying water. Further, this tube is after a short
time filled with a whirling mass of vapours densely
crowded together, or it may be of water, which
rushes upwards with a most furious motion, with
spiral revolution, and a remarkable roaring noise, as
is shown in the aforesaid figure. After about ten
minutes, a part of the tube, a third say, or a half, is
often broken off, and when this happens, the waters
rush down in immense quantity — a fearful sight to-
behold — and ships are sometimes sunk by them.

d^ d^ is the cloud from which the said tube is seen
to descend. It is at its first appearance small and
thin, but it soon expands widely in all directions, and
at last, when it has become exceedingly dense and
gloomy, it dissolves in a violent storm of rain. Sq
much then by way of description of the phenomenon^
It now remains for me to show next the way in which
it is produced by a whirling movement of the air
and by its diminished pressure.

And here in the first place I take it for granted
that the air is sometimes driven round in a circle^

On Sal Nitrum and JViiro- Aerial Spirit 127

whether as the result of winds rushing from opposite
directions, and at length dashed against each other
and bent into a circular path, or as the result of their
being suddenly thrown back by the resistance of lofty
mountains or of dense clouds, or in the manner
indicated in the previous chapter.

2. It is to be observed that aerial particles when
revolving in a circle, try to recede from the centre of
their motion, as was observed long ago by Descartes.
Hence if we suppose that a cylindrical column of air,,
reaching from the summit of the atmosphere to the
water beneath, is made to rotate, and if that aerial
vortex is large enough and is carried round with a
very rapid rotation, the total force by which all the
particles of that aerial vortex strive to depart from the
centre of their motion will be great enough to resist
the pressure of the surrounding air and even to over-
come it. But if this happens, and the aerial particles
recede from the centre of the vortex, the middle of it
will be like an empty tube : for the case will be
exactly like that in which a large number of globules
are placed in a concave circular vessel and made to
rotate rapidly with it, when you will see these globules
go away from the centre of the cavity and describe
their circular orbits at its side.

But now when a vacuum is made in this way in
the middle of the air-vortex, the water which lies
beneath will be forced to ascend by atmospheric
pressure, just as it would be into a vacuous tube.
Nay, although the aerial cylinder may not rotate with
so swift a motion as is needed for completely over-
coming the pressure of the surrounding air and pro-
ducing a vacuum in the middle of the vortex, still, with
however feeble force it rotates, the weight and pres-
sure of the air will certainly diminish gradually from

128 Mayow

the outer edge of the vortex to its centre. For let
a^ a^ h^ 3, in the aforesaid figure be the aerial cylinder
extending from the summit of the atmosphere to the
subjacent water. While as yet it was not in rotation,
the pressure of the air of which it was composed is
certainly quite equal to that of the atmosphere, since
their weights were in equilibrium ; but now when the
aerial cylinder is made to revolve, the force with which
each particle in rotation strives to recede from the
centre of its motion is added to the original pressure
of the cylinder. Hence it is that these forces in union
will preponderate over the pressure of the surrounding
atmosphere, and therefore the adjoining air will be
pushed out by the revolving air, and will necessarily
recede somewhat, say from a to 2, and from b to g^ and
consequently the rotated air following it will spread
out into a larger space than before and constitute the
cylinder i^ /, g^ g. Hence the rotated air is not a little
rarefied, and consequently the water beneath is less
pressed by it than before.

That the pressure of the rotated air gradually
diminishes from the outer edge to the centre of the
vortex, I gather from the following. For when all
the particles of the aerial whirlpool strive to recede
from the centre, it results that they impel and press
against the particles of air adjacent to them on the
outside ; while, on the contrary, the air between them
and the centre of the vortex is subjected to less pres-
sure from them now than while as yet they had no
<;ircular motion and no tendency to recede from the
centre of their motion. But since the rotated air, in
proportion to its nearness to the centre of the vortex,
suffers less pressure, it follows that the air particles,
the further they are within, expand and rarefy the
more, by virtue of their elastic force, and conse-

On Sal Nitriun and Nitro- Aerial Spirit 129

quently press less on the water which lies under them.
Whence it is that the water rises gradually from the
inner edge to the centre of the vortex, the water
rising more in that part of the vortex where the
rotation is more rapid, as is shown in the figure.

I remark here that it is probable that at the base
of the mass of rising water, the water, as shown in the
figure, is somewhat depressed (although this, perhaps,
can scarcely be seen by sailors at a distance). For
when the air surrounding the first cylinder, a^ a, h^ 3,
is thrust from a to / and from h to g^ in the manner
aforesaid, the result is that the air at i and g^ being
much compressed, undergoes considerable condensa-
tion, and in consequence the water beneath will be
somewhat depressed by the greater weight than usual
of superincumbent air.

With regard to the fog that rests upon the pile of
waters, I think it is caused in this way. Thus since
the air about the surface of the rising water rotates
very rapidly, the water, at the outer parts at least, is
carried round along with the air ; whence it comes
about that small particles of the water, receding from
the centre of their motion, are dispersed in all direc-
tions and borne upwards, just as would happen if a top
with its upper surface spherical were wetted with
water and made to spin.

But the reason why those vapours, as shown in
the figure, are bent and at last unite in the torrent at
^, e^ seems to be this, that the nearer the rotated air
is to the centre of the aerial vortex the more it is
rarefied and thinned, as has already been shown. For
hence it is that while the aqueous particles driven away
from the aforesaid mass are carried upwards and out-
wards, they are at every instant of their progress bent
inwards by the air, which gradually becomes denser

I

130 Mayow

from the centre of the vortex to its outer edge, but
where the air is rarer the aqueous particles can more
easily continue their movements ; and, turned back
in this way, they arrive at last at the middle of the
aerial vortex (which behaves like a vacuous tube), and,
congregated densely there, are carried aloft in a
swift whirl and spiral revolution, as is shown in the
figure. Moreover the spiral motion of those vapours
arises from the circular motion of the surrounding air.
To bring the said vapours to the middle of the aerial
vortex, and thence to raise them on high, the pressure
of the atmosphere seems to contribute not a little, in
addition to the force by which they have been torn
from the mass of water. For since the air at the
summit of the atmosphere is much rarer than that
which is nearer the earth, and its pressure less, and
since, also, the aerial vortex rotates there more rapidly
(for the force which constrains the air to rotate prob-
ably comes from above), it follows that the force by
which the aerial particles strive to recede from the
centre of their motion will take effect much more
easily at the summit of the atmosphere than near the
underlying water ; so that high up in the air where,
namely, the said tube is seen, the aerial particles
recede from the centre of the vortex and are able to
produce a vacuum there, whereas the air from the
lower end of the tube to the underlying water, being
rotated less rapidly, is merely able to diminish the
pressure of the atmosphere, which is greater there,
but not altogether to remove it ; and hence, the air
and vapours at ^, e (where the vacuous tube begins),
are driven forcibly into the tube by the pressure of
the surrounding air. Further, as all the neighbour-
ing particles of air and vapours come into the place
of those that have been carried up, and others again

Oil Sal Nitrum and Nitro- Aerial Spirit 131

follow them, it comes to pass that vapours are
<:arried in a continuous stream towards the centre of
the vortex.

About the said tube, it is noteworthy that at first,
when, namely, the whirl of vapours is not yet observed
in it, it looks like a rather thin smoke and also gradu-
ally descends, while yet it would seem that the vapours
entering its lower end would cause it to be seen there
first. I think the reason of these things is that when
the air first began its rotating movement, only a few
rather thin vapours — those, namely, which, already in
the atmosphere, were carried upwards — had entered
the said tube. And these are first seen at the top of
the tube because they are assembled there in greater
abundance,and are alsosomewhat condensed on account
of their diminished velocity. However, I do not know
whether or not these things depend also on another
cause, for, since the air receding from the middle of the
vortex leaves the tube there nearly vacuous, the aerial
particles, and there are but few remaining in it, will
as they expand, appear under the form of smoke, not
otherwise than it happens in a glass vessel when the air
is being exhausted by Boyle's pump, as will be explained
more fully elsewhere. And it seems to be for this reason
that the smoky tube is first seen high in the air, where
the force by which the rotated air strives to recede
from the centre of its motion first takes effect and
produces a vacuum, as has already been shown.

It is besides to be noted that the nearer to the
water the said tube descends, the higher does the water
underneath rise. And the reason of this seems to be
that a long descending tube cannot be formed unless
there is a very swift whirl of the air, and the ascent
of the water depends on this.

When the vapours driven up in the said tube have

132 Mayow

come to the top of the aerial vortex, they, receding
from the centre of their spiral motion, are dispersed all
around, and, heaped up in great abundance, form the
dense and gloomy cloud widely spread for a short time
(</, d). This, after the motion of the vapours of which
it consists has ceased, breaks up in a storm of rain, and,,
pressing by its weight on the underlying air and push-
ing it out, causes the violent wind. But it is to be
observed that although at some distance from the
aforesaid mass of waters, boisterous winds blow and
the sea is very rough, yet near the phenomenon all is
calm, which I think may thus be explained. Since the
air is very dense at the outer edge of the vortex, as is
seen in the figure, and is thrust out all round from the
aerial vortex by the pressure of the superincumbent
cloud, the wunds carried towards the vortex are arrested
and turned back by the air, which is very dense and also
rushes in the opposite direction, so that their impulse
cannot reach the vortex, yet meanwhile these winds
driven backwards cause furious whirlwinds at some
distance from the said phenomenon.

It also makes for this, that the sea near the column
of rising water is whirled round — a motion in water
very much opposed to the propagation of waves, which
advance only in straight lines.

After the mass of water has again fallen, a certain
part of the said tube is usually broken off, and when
this happens a vast quantity of water descends from on
high, and if a ship happens to be under it she is in-
stantly overwhelmed and sunk. There can be no
doubt that the water is produced by the condensation
and collection of the vapours which have risen in the
tube. But such a heaping up of them comes from this
that when the motion of the aerial whirlwind has
abated, the vapours at the top of the tube, ceasing

t

On Sal Nitrum and Nitro- Aerial Spirit 133

from their motion and being condensed into water,
are carried down and encounter others which are still
ascending at the bottom of the tube, and at last fall
down along with them.

But here we must ask why, on the cessation of the
circular motion of the air, the elevated vapours presently
fall ; because, although the motion of the air by whirl-
ing the water underneath was the cause of its fine
particles being carried up, yet, after these vapours have
been once set in motion, the whirling motion of the air
seems to contribute nothing to their ascent, unless
perchance the air is reflected upwards by the water
underneath.

In regard to this, it is probable that when the
circular motion of the air gradually abates, the
aqueous particles do not, as before, leave the aforesaid
mass of water with a force intense enough to raise
them as high as the summit of the atmosphere, and
therefore these vapours must be heaped up in the
manner already described, and rush downwards ; while
yet, if the whirling motion of the air has suddenly
ceased, the vapours, violently agitated, ascend beyond
the top of the tube and are dispersed there, so that
the tube (as is sometimes the case) will seem to
ascend aloft. To this I add further, that so long as
the circular motion of the air continues, the pressure
of the atmosphere contributes somewhat to drive the
vapours upwards into the tube, as was previously said.

About the said phenomenon we remark in fine that
if it should happen that the aforesaid tube rise right
above an island or sea-coast, its lower end will be
driven back from the island or coast, sea-wards, as is
delineated in Plate VL, Fig. 2. But that the reason
of this may be understood, let «, «, be a section of the
aerial cyHnder in rotation, which is interrupted at its

134 Mayow

lower end by the interposition of an island, as is seen
in the figure. For the air near the island, rotated from
b towards d^ when it has reached the island at <;, can
advance no further in that circle ; since therefore the
rotating air is pressed also by the external air adjacent
to it (and this, as has been already pointed out, is.
much condensed), it will necessarily be reflected
towards ^, where on meeting the air that has been
carried from h towards d^ it forces it outwards and
is turned round along with it towards/ And so, the
first vortex being interrupted, a new vortex, ^, /
emerges, in the centre of which the column of water
rises, as is shown in the same figure. But that new
vortex coming, at some height above the sea, say at
/, against the former ^vortex which is rotating with
the opposite motion, is by it, as being the more
powerful, gradually turned back, so that both
ultimately coincide at «, a.

CHAPTER XII

OF LIGHT AND COLOURS

We have already treated of nitro-aerial spirit so far as
fire is kindled by it ; it remains for us to subjoin some
things about light, the peculiar and most wonderful
offspring of fire. With regard to rays of light, it can
scarcely be believed that certain effluvia of more
delicate flame, shot out from the luminous body^
reach the beholder's eye. For who can imagine that
any fiery corpuscles can be brought, almost in a
moment, from the sun to the earth ? Much less is
it probable that fiery particles emanate from a small

k

On Sal Nitrtim and Nitro- Aerial Spirit 135

lamp in quantity sufficient to illuminate the region
round about. Nor again is it to be thought that
finer sulphureous particles, flying away far from the
original blaze, excite other (nitro-aerial) particles for
the kindling as it were of a very meagre flame,
namely Light, as the distinguished Willis and others
have supposed. For if such were the case, why should
the light not endure for a little after the extinction
of the lamp ? For it seems to me that the sul-
phureous particles proceeding from the lamp just
before its extinction, would continue to produce light
until they arrived at the extreme limit of the illumi-
nated region, for the sulphureous particles which
emanate from any burning body do not resign their
fiery nature until they have ascended to the furthest
limits of the flame. Hence the flame of a lamp
usually continues for a short time after its sulphureous
matter has been entirely consumed, as was shown
above. Yet since the sphere of the blaze is but small
and the fiery particles pass through it in an instant,
hence it is that the flame quickly expires. As,
however, the sphere of light is much wider, it would
seem that the luminous particles cannot pass through
it so quickly but that the light should continue for
some time after the lamp has been removed or
extinguished. Further, if light were a somewhat
finer flame, what should prevent it from being
deflected hither and thither by blasts of wind like
flame, in proportion to its consistence, such as that
may be? And how, lastly, could rays of light be
transmitted instantaneously through the most solid
bodies such as glass, if light were propagated by means
of sulphureous particles ? For even the extremely
small and nimble nitro-aerial particles do not pene-
trate bodies so solid, without some interval of time,

136 Mayow

even when they move with the swiftest and most
fiery motion. How much less then will sulphureous
particles, which seem to be grosser than nitro-aerial
spirit, penetrate such bodies in an instant ?

I may therefore maintain with the distinguished
Descartes that light consists in motion or impulse
alone, which, because of the continuity of the lumi-
nous medium, is transmitted to the greatest dis-
tance without any delay. For certainly impulse or
motion is eminently adapted to the laws which are
followed in the propagation of light. For the nature
of impulse is such that it will promptly cease when
the impelling force is withdrawn, and it advances only
in straight lines. Further the force of impulse is
propagated instantanepusly to the greatest distances
through solid bodies. For the case here, owing to
the continuity of the medium, is just as if one end of
a rod being moved, the blow impressed on it were
transmitted almost instantaneously to the other very
remote end.

As to the medium by the impulse of which the
rays of light are transmitted, it is not to be believed
that it is air itself, since light can be propagated very
intensely even in a glass vessel containing no air.
And therefore it is probable that besides the nitro-
aerial particles fixed in the aerial particles, other nitro-
aerial particles are interspersed among them and fill
all their interstices ; which we infer from this, that
solar rays, if collected by means of a burning-glass,
actually ignite even in a glass from which the air is ex-
hausted. For gunpowder can be ignited by them there,
and sulphureous matter can also be sublimed by their
heat ; but I have already attempted to show that heat
and fire do not arise except from nitro-aerial particles
set in motion. Thus it would seem that even in a

I

Oft Sal Nitrum and Nitro- Aerial Spirit 137

place deprived of air there are nitro-aerial particles,
and that the fire produced there by the solar rays, con-
centrated by means of a speculum, consists in this,
that the nitro-aerial particles are so much impelled
at the point where the solar rays meet that they
are thrown into a really fiery motion. So that the
medium by whose impulse the rays of light are propa-
gated seems clearly to be nothing else than nitro-
aerial particles very densely distributed through the
atmosphere. Indeed it is probable that nitro-aerial
particles when moving in a luminous body with a
very rapid and fiery motion, communicate to the
other nitro-aerial particles, dispersed through the
ether and of the same nature as themselves, the
peculiar impulse by which the rays of light are
propagated.

But you will say, if nitro-aerial particles exist in a
place void of air, why cannot a lamp be kindled and
burn there since no requisite is lacking for the pro-
duction of flame. I answer that the sulphureous
particles of a lamp contribute in no way to produce
flame, except in so far as they strike out from aerial
particles, the nitro-aerial particles which, sundered with
violence, are thrown into fiery motion, as was pointed
out above. But sulphureous matter seems to be by
no means fit for throwing into fiery motion the nitro-
aerial particles disseminated through the ether.

Like igneous particles, so also moving particles of all
substances whatsoever which give an impulse to the
luminous medium in the due way, are capable of pro-
ducing light. Hence it is that a kind of feeble light is
emitted by the glow-worm, by rotten wood, and the
like.

Further that light is propagated by the impulse of
nitro-aerial particles seems to be confirmed by its pass-

1,38 Mayow

ing with greater ease through such bodies as are ex-
tremely rigid and crammed with nitro-aerial particles-
— glass, for instance, and similar substances, but above
all, aerial particles whose rigidity is due to nitro-aerial
particles densely infixed in them, as I previously
endeavoured to show.

Here too we can appeal to an experiment re-
ferred to by the Hon. Robert Boyle ; to wit, when
air is suddenly pumped from a glass vessel, the glass
soon becomes dark inside and seems to be filled with
nebulous fumes, and besides light, or rather a certain
momentary whiteness, is sometimes produced in it.
This I think is to be accounted for by the immediate
expansion of the residuary particles of air, when the
greater part of the air \s pumped from the glass ; not
otherwise than as steel springs which have been bent
round coil upon coil, open out in a moment as soon
as the force by which they were bent is with-^
drawn. But when aerial particles extend themelves in
this way, their structure changes at each successive
moment in which the movement of recoil takes place,,
(as is evident from what has been said on the subject
of elasticity) ; whence it is that the rays of light are
somewhat interrupted, for, namely, the nitro-aerial
particles infixed in the aerial particles, by whose im-
pulse moreover light is transmitted, move with a
motion different from that by which the action of light
is propagated ; so that the aerial particles cannot now
transmit the impulse of light as they would otherwise
do, but reflect it in the manner of a mirror. But as-
soon as the aerial particles cease from their motion of
recoil, the glass becomes again pellucid.

OF COLOURS
But with a view to a clearer understanding of the

I

On Sal Nitrum and Nitro-Aerial Spirit 139

nature of light, let us make a brief investigation of
the quality of the colours which are produced by light.
With regard to colours and the visible forms of
things, it is the most generally received opinion that
they are produced by the rays of light reflected in
various ways. But indeed I am not sure that this
way of explaining colours is quite in accordance with
truth. For let us suppose that a lamp is placed out-
side a chamber so that the rays of light, by means
of two apertures made in opposite walls of the chamber,,
may pass through the intervening space. When this
is done, if the eye be placed in any part of the chamber
except that through which the bundle of rays passes,.
the chamber will appear completely dark and the rays
of light passing through it will not be seen at all. But
now, let us suppose any coloured plane 3, Plate I.,
Fig. II, to be placed obliquely to the rays passing thus
through the chamber ; when this is done, the plane will
be illuminated and by an eye placed at a will be seen
of some colour, suppose white ; and yet it seems that
the rays of light are not reflected to the said eye. For
if that plane is polished in the manner of a mirror and
suitable for the reflection of rays of light, the rays
falling upon it will, from its oblique position, be
diverted from the eye and reflected to the opposite
side of the chamber, towards c, to which the line of
reflection tends. One would naturally say that a
coloured surface, especially a white one, has little
swellings or molecules most densely crowded upon it,,
whose innumerable very small surfaces look in all
directions around ; and that the rays of light falling
upon these very small surfaces, which are turned
towards the eye wherever it is situated, are reflected
by them, as by so many mirrors, to the eye, and im-
press upon it the sense of colour. And hence it is that

140 Mayow

if the aforesaid plane were extremely smooth, so that
all the rays falling upon it were reflected towards c^
the plane could not be seen at all by an eye situated
at « ; so that it appears that an image of the plane is
propagated by certain rays reflected to the eye. But
this answer seems unsatisfactory, for if the rays of
light falling upon the said plane were reflected in
that manner in every direction, then almost the whole
chamber would be illuminated by reflected rays, just
as the chamber at c will be lighted up if the said plane
is polished and capable of reflecting the rays of light.
For since we suppose the plane to appear white, the
rays of light ought to be reflected all round in no small
amount, for white is supposed to be produced only
when the rays of light^are very densely reflected. But
in fact, although the said plane is seen as white by the
aforesaid eye, yet the eye will be all the while in dark-
ness, and will not be able to discern what is nearest
to it. And yet if the eye were placed at c, where,
namely, the rays reflected from the polished surface
tend, it would be dazzled with light and would see
everything near it illuminated by reflected light.

Besides it would follow from this hypothesis that the
rays of light so reflected from any white surface are
more dense than those which emanate from fire or any
flame of a red or less white colour. For it is supposed
that the intermediate colours, such as red and others
of that kind, are produced by light and darkness
variously intermixed, while white results from light
when most densely reflected. But this is by no means
the case ; for if a reddish fire, such as that of burning
coals, were kindled in the said chamber, the whole
chamber would be illuminated by its rays, while the
colour white is propagated with scarcely a trace of light.
Still I would not deny that a white surface reflects

On Sal Nitrtim and Nitro- Aerial Spirit 141

some rays of light, in so far as it is polished in some
parts and fitted to reflect the rays of light. But it is
scarcely credible that the rays of light are reflected
from a white surface in such abundance as is requisite
for producing a white colour all round. But the reason
why the said plane cannot be seen if it is highly
polished is to be looked for in what is said below. •

Further, it appears that the luminous body itself is
not seen by the rays of its own light, whether direct or
reflected. For a small lamp burning in a high place
can be seen clearly enough several miles off, far be-
yond the bounds of its illumination, by an eye in a
dark place. But this would not be if an image of it
were produced only by rays of its own light.

But to submit my own view on this question, I think
it is to be held as at least a probable conjecture that
the image of a small lamp, seen beyond the limits of
its illumination, is propagated by a peculiar impulse
which is quite different from the impulse of light.
Indeed igneo-nitrous particles when violently agitated
in a luminous body, in so far as they strike and move
other nitro-aerial particles kindred with themselves
and these in their turn strike and move others, con-
stitute the action of light, as I tried to show above ;
but in so far as these igneous particles impel a peculiar
medium, distinct from the luminous medium, and im-
press upon it a sort of special undulation or impulse,
they seem to diff'use in all directions a visible image
of themselves. For it is probable that particles, igneous
and luminous per se^ and with their own motion,
do not affect so much the sense of sight as of touch.
For fiery particles cause very great pain, and the eye
when exposed to too fierce a light is injured as if it
were struck by some blow. Further, the solar rays
strike not only the eye but also the nostrils exposed

142 Mayow

to them, and, by tickling them, cause sneezing. But
luminous particles seem to propagate the image of
themselves by the very gentle impulse of a peculiar
extremely fine medium. And this when conveyed
by a continuous undulation of the medium of vision
to the eye, and by means of it to the delicate origin
of the optic nerves, impresses on them such strokes
as are appointed by nature for producing the image
and the perception of light. Nor is it necessary for
the perception of Hght and colours, as the very acute
Descartes pointed out long ago, that a material image
resembling the ideas which we form in our minds of
objects, should pass from them to the eye, since in-
deed, to produce the different sense perceptions in the
mind it is only necessary that the fine nerve threads
which proceed from the brain should be agitated with
various motions. For in this way a blind man who
uses a stick to guide his steps, feels and distinguishes
well enough, by the various ways in which the stick is
moved when it strikes against bodies of all sorts,
whether it is a tree, or a stone, or anything else that
opposes him.

As the likeness of a luminous body, so also the
image and visible form of an illuminated body appear
to be propagated by the motion of a special medium
distinct from the action of light. For when the afore-
mentioned plane, exposed to the rays of light, is seen
by an eye placed in darkness, its visible form is con-
veyed to the eye not by reflected rays of light, since
these do not reach the eye, but by the motion of a
peculiar medium quite different from the action of light.
But the mode in which this special medium is moved
will be treated of later.

As to the medium by whose impulse the likenesses
of things are propagated, it is probable that it consists

IK

k

On Sal Nitnim ana Nitro- Aerial Spirit 143

of finer matter compacted with greater continuity than
the medium by which the rays of Hght are transmitted.
For we must suppose a very subtle and ethereal matter
which, interwoven with the nitro-aerial particles, oc-
cupies and fills up all the interstices of the atmosphere,
and that by its impulse visible forms are propagated.
In fact, the structure of the eye is so tender and
deHcate that it is able to perceive those very gentle
blows of ethereal matter, imperceptible to the other
senses, and besides to distinguish the variation in its
pressure and rhythm on which vision and colour depend.
And indeed it seems to be owing to the extreme
tenuity of the medium of vision that the image of a
lamp is conveyed to such a great distance without any
delay. For the visible form of a luminous body is
transmitted far beyond the limit of its light, and
probably with a swifter motion than the rays of light
are transmitted through the air.

That the image of an illuminated body is trans-
mitted by the impulse of this special medium, and by
a motion different from the action of light, I have en-
deavoured to show above. Let us therefore now
consider next, how it is that the medium of vision is
struck. On this point I was for some time in a
difficulty as to whether it is by the impulse of the
illuminated body or of the luminous particles that the
medium of vision is affected. For I think we must
maintain either that the luminous particles imping-
ing on the surface of the illuminated body, impress
such an impulse upon it as is fitted, when conveyed
through the medium of vision and by its instru-
mentality to the eye, for presenting an image of
the illuminated body, or (as seems to me more prob-
able) that the nitro-aerial and luminous particles
falling upon the illuminated body, acquire themselves

144 Mayow

a certain new motion, by which the medium of vision
is struck with an impulse distinct from the action of
light. For we notice that the rays of light do not,
like igneous particles, spread their image in all directions
around. For when the rays of light pass through the
aforesaid chamber, they are seen only by an eye which
directly faces them but not, as we showed above, by
an eye situated at the side. Whence we may infer
that nitro-aerial particles in a burning body are some-
how driven round in a circle, and in their circular
motion strike the medium of vision all round, but that
the luminous particles move only in straight lines, so
that, whether by very frequent blows or by a kind of
pressure, they impel the visible medium directly
forward only, but not^ to the side. And indeed the
action of light tends to move straight forward, pre-
cisely as if it were projected in a straight line ; for the
rays of light, when they strike upon a plane, are re-
flected like a solid body at an angle of reflection equal
to the angle of incidence. But when luminous par-
ticles impinge on an illuminated body they probably
acquire a new tremulous motion and are moved with
very short and frequent vibrations, precisely as happens
to a dart when it is thrown and one end of it strikes
a solid body. Hence it is that the medium of vision is
struck by the vibration of luminous particles even on
the sides and in all directions. But since this sort of
vibration of the luminous corpuscles varies according to
the diversity in the surface of the illuminated bodies, and
since, in fine, the medium of vision is differently impelled
by it, hence it is that the diverse perceptions of colours
and of images are produced and propagated all round.
With respect to the glittering white colour which
a brightly shining lamp shows, it seems to depend on
this, that the particles of the shining body, agitated

I

On Sal Nitriim and Nitro- Aerial Spirit 145

with the swiftest motion, and in densest array, strike
with vivid action the very subtle medium of vision in
individual points, with no interruption, and by this,
transmitted to the eye, the perception of light is
caused. Moreover the variation of this glittering
whiteness results from the interruption of the impulse
of the very subtle medium at certain points by opaque
bodies interspersed in the medium.

The white colour, which most nearly approaches
glittering white in brightness, does not seem to
depend, as is commonly supposed, on an extremely
dense reflection of the rays of light. For, as I have
endeavoured to show, all colours are different from
the action of light.

It seems, therefore, that we should maintain that
the white colour arises from this, that the luminous
particles impinging on the illuminated surface, en-
counter in its very many points such a resistance that
these particles are, in consequence, excited to some
new tremulous motion with very frequent vibrations,
as we have just shown. And by these very
numerous particles, made to vibrate in this manner,
the medium of vision is struck very frequently and at
very many points with an impulse different from
light ; and in this way the white colour seems to be
produced. And hence, since a white surface has
usually many very minute excrescences distributed
thickly over it — not that these reflect the rays of
light (for rays of light are scarcely reflected at all
from a white surface such as paper, but on the
contrary the impulse of light is quite destroyed by it,
as was shown above) but so far as the very numerous
luminous particles falling on these molecules acquire a
certain new vibration by which the very subtle medium
of vision is struck in very many places — the white

K

146 Mayow

colour is propagated. But on the other hand if the
rays of light are entirely absorbed, without resistance,
by the surface of the illuminated body, or if the solid
body is of such a kind as offers little resistance to
luminous motion, black colour or rather the absence
of all colour is the result. For example, if an eye
situated in darkness is turned towards an illuminated
mirror, but in such a position that the rays falling on
the mirror are not reflected to the eye, the mirror will
appear of a black colour, or rather it will scarcely be
seen at all. Nay, although the mirror be so placed
that the rays of light reflected from it fall upon the
eye of the beholder, the rays will indeed flash like
lightning upon the eye, but the glass itself will
scarcely be seen at ,all. No doubt the luminous
particles impinging on the mirror, throw the nitro-
aerial particles which the glass contains — and which
are kindred with themselves — into their own
luminous motion, for it has elsewhere been shown
that very solid bodies, such as glass and the like,
have nitro-aerial particles inserted in them. But
since the particles of the glass yield to the motion of
the luminous particles and in no way resist it, these
luminous particles will acquire none of that motion of
vibration by which colours and the images of things
are propagated ; hence it is that glass of that kind
has no colour at all.

As to red and the other colours which differ from
the glittering white, they seem to be due to various
mixtures of the glittering white with darkness.

From what has been said, we must seek for an
explanation why substances of a white colour can
scarcely be kindled by solar rays collected by a
burning-glass, while, on the other hand, such as are
black easily take fire. For when nitro-aerial and

Oil Sal Nitrum and Nitro- Aerial Spirit 147

luminous particles, impinging on a white surface,
acquire the new motion by which the white colour
is propagated, they lose entirely their luminous and
fiery impulse ; but it is otherwise when they fall on
a black surface.

Finally, we note also here that the impulses of light
and of colours follow almost the same laws ; for colours
and images of things (although they are propagated
laterally and in all directions, as was shown above)
proceed, like the rays of light, only in straight lines,
and further, like light, they undergo reflection and
refraction.

CHAPTER XIII

OF LIGHTNING

Having now treated of fire and light, let me add a
few remarks on lightning, since it seems to waver
between flame and light.

In the first place then as to lightning, it is not to
be supposed that any flame discharged from a flashing
cloud reaches the eye. For who can conceive a flame
so vast and swift as to spread in a moment over
almost the whole hemisphere. Nor can it be said that
the sulphureous exhalations which are raised by the
sun's heat and widely dispersed through the atmo-
sphere are all kindled together by the flame of the
flashing cloud, for if it were so these sulphureous
exhalations, when once kindled, would burn till they
were totally consumed ; and, consequently, since the
sulphureous particles would be used up the first time,

148 Mayow

there would be no second flash. And indeed the
flash would continue for some time ; but the opposite
is the case.

Should any one here say that the sulphureous ex-
halations, which are imprisoned here and there among
the clouds, are separately kindled in consequence
of their being violently agitated, and that the flash of
lightning is due to the wide expansion of their light ;:
I reply that it is scarcely probable that a fire so im-
mense as to be capable of propagating light to such
vast distances, is produced by a succession of separate
flashes, for it is to be noted that lightning is not
only seen at a distance, but reaches to the eye of the
spectator. Further, if lightning were nothing else
than rays of light, how does it happen that it not in-
frequently sets fire to things which it meets ? For this
is never done, even by the solar rays, except when
collected by a burning-glass. And from what source
finally should the power come, which is required for
the effects usually produced by lightning, if it consisted
merely of light ?

I confess for my part that sulphureous exhalations
disseminated through the air are not infrequently
kindled by lightning, but the flame produced by their
burning is quite diff"erent from a flash of lightning,
and is propagated hither and thither in a skirmishing
way, as it is led by the exhalations, and it also lasts
for some time. Such a flame is sometimes seen in a
very intense flash.

But that it may be understood what I think about
lightning, it is allowable for us to assume that thunder-
storms are caused by this, that the clouds high up
in the atmosphere, when condensed and frozen, descend
on those beneath with a violent crash, as has been
shown by the very ingenious Descartes. Further,.

On Sal Nitruin and Nitro- Aerial Spirit 149

when the clouds dash violently against one another
in this way, the air around is necessarily thrown into
a tremulous motion ; and this agitation of the air is
conveyed, with scarcely any loss of time, to a great
distance, on account of the continuity of the atmo-
sphere. Nay, in whatever manner thunderstorms are
produced, the air must certainly be agitated with a
very great commotion.

Now I certainly think it is probable that the aerial
particles, since they are solid and rigid, strike forcibly
against each other in consequence of the violent
concussion of the air produced in a thunderstorm,
and that they wear themselves by the powerful and
sudden mutual shock. The consequence is, that the
nitro-aerial particles, struck out from the aerial particles
and thrown into a fiery motion, produce a certain light
and momentary flame (such as that of lightning is)
which extends over nearly the whole hemisphere.
For it is very much as though an immense congeries
of very small flints were struck with so violent a blow
that an almost infinite number of sparks of fire should
be struck out from the collision of its innumerable
particles ; for in this case a certain light flame, pro-
pagated through the whole aggregate of flints, would
be suddenly kindled. Besides 1 do not know whether
or not the nitro-aerial particles disseminated among
the aerial particles (from some sort of impulse of
which, I assume that light arises) can be thrown by
the violent concussion of the atmosphere into such
a motion as is requisite for the production of light.
And indeed if lightning were light and nothing
more, it would seem to be due sometimes to this
cause.

As to the fervent and very intense sultriness, which
often precedes thunderstorms, it must not be thought

150 Mayow

that it results from sulphureous exhalations carried
aloft and dispersed through the air ; for that kind of
sulphureous matter can only become heated, or con-
tribute to the production of heat, by first being kindled.
Therefore I think it should be held that the said
sultriness is not infrequently the result of a tremulous
and unequal movement of the air ; for the air, when
agitated by a motion of that kind, becomes very warm
as the distinguished Descartes has remarked. For if
any one blows vigorously against the back of the hand
the breath is felt to be very cold ; while, on the con-
trary, if he blows it into the contracted and bent palm
of the hand, it becomes not a little warm ; the reason
seems to be that when the aerial particles are thrown
into a tremulous motipn by being reflected hither and
thither in the hollow hand, it happens that the nitro-
aerial particles, by their striking against each other^
are gently detached and thrown into the motion that is
required for heat. But if a considerable tract of air is
at any time agitated by such a motion, it will not only
grow warm but will also be in a condition for entering
upon a motion of the kind required for the production
of lightning.

As regards the wonderful violence with which
lightning sometimes overthrows and burns whatever
stands in its way, the distinguished Gassendi very in-
geniously supposes that glomeres (as he calls them)
consisting of nitrous, vitriolic, and sulphureous ex-
halations, together with a small portion of cloud
gathered round them, descend to the earth, and that^
when they take fire at last, they burst into a very im-
petuous flame and destroy everything they come near.
But, indeed, not to say that nitrous or vitriolic vapours
do not exist in the air (as I endeavoured to show above),
it is scarcely probable that a small portion of cloud (if

On Sal Nitrum and Nitro- Aerial Spirit 1 5 r

it descended to the earth in that way) could imprison
inflammable matter with force sufficient for the stroke
of a thunderbolt.

Wherefore we may assume that the immense
force of lightning is produced in the following way.
For instance, if a tower or other obstacle stands, at any
time, directly in the path of the rush of air (for it is to
be observed that, in a thunderstorm, the air pressed
by the descending cloud spreads out one way or other),
it happens that the air is brought to a stand by
the opposition of the said things and is greatly con-
densed, as is shown in Plate I., Fig. 10. And not only
the aerial particles but the sulphureous also, which
are raised into the air by the great heat of the sun, are
densely collected near the obstacle. But in conse-
quence of the dense collection of the particles of both
kinds, and their igniting in the manner aforesaid on
account of the violent concussion of the air, a globular
fire, and that very impetuous and rivalling gunpowder,
is produced. For it has been shown elsewhere that
the force of gunpowder is caused by nitro-aerial
particles bursting out in densest crowd from the
ignited nitre. Accordingly, since aerial particles are
charged with the same nitro-aerial particles, if they
ignite when densely collected, the flame produced by
them will be very impetuous for the very same reason
as in the case of gunpowder ; so that now it is no
wonder that a thunderbolt sometimes overwhelms
and prostrates whatever it meets.

In what has been said, we must look for the reason
why a thunderbolt sometimes melts a sword, while
the sheath is left intact. No doubt, since the motion
of the air excited in thunder shakes even solid bodies,
it sometimes happens that iron and other solid bodies
against which the force of that motion is specially

152 Mayow

directed are so agitated that the nitro-aerial particles
which they contain (for we have shown elsewhere
that rigid bodies such as iron, abound in nitro-
aerial particles) are greatly disturbed and thrown into
a fiery motion, and in consequence of this movement
of the particles the structure of the substances in
which they reside is destroyed. And the more solid
bodies are, and the more they abound in nitro-aerial
particles, the more quickly are they consumed when
struck by lightning ; for the particles of the more
solid body strike more violently against one another,
and agitate themselves the more. Hence it is that
the iron is melted by lightning while the scabbard, on
account of its loose texture and the want of nitro-aerial
particles, remains uninjured. Thus the very strength
of bodies tends sometimes to their destruction and the
strongest things perish the sooner from internal dis-
cords and movements.

It is also noteworthy that animals are often killed by
lightning without showing any trace of a blow. This
seems to be due to the fact that aerial particles — not
those alone which are disseminated through the air,
but those also which exist in the mass of the blood —
are thrown by the violent concussion of the air into a
kind of flash, in consequence of which they immedi-
ately become effete and altogether unsuitable for
keeping up the fermentation of the blood. To this I
add that the animal spirits are also dissipated by
lightning, as will be shown elsewhere.

Lastly, with regard to the impetuous and whirling
winds which usually accompany thunderstorms, they
seem to be caused not merely by the air being
violently thrust forth by the pressure of the descend-
ing cloud, but also, to some extent, in consequence of a
vast tract of air being deprived of its elastic force and

On Sal Nitrum and Nitro-A'erial Spirit 153

pressure, whether owing to the nitro-aerial and elastic
particles struck out of the aerial particles colliding with
each other in thunder, or on account of sulphureous
exhalations kindled here and there throughout the
air ; for aerial particles when deprived of nitro-aerial
particles, whether by combustion or in any other way,
lose their elasticity, as was previously pointed out.
Hence it is that the air, rushing from every quarter, is
borne with rapid motion to that place where the
pressure of the air is diminished. But these aerial
torrents rushing from opposite points produce, in their
passage, a sudden and impetuous wind, and when at
last they meet and dash against each other they are
bent in all directions and driven round in a circle,
since the air rushes from all directions and allows no
outlet for their escape ; and this seems to be the
cause of the violent whirlwinds which suddenly arise.

I

CHAPTER XIV

OF THE HEAT OF QUICKLIME. INCIDENTALLY OF
THE COMBINATION OF OPPOSITE SALTS

Now that we have discussed nitro-aerial spirit in so
far as it is the cause of fire and heat, it will not be out
of keeping with our plan to treat of quicklime, in
which, when it is sprinkled with water, nitro-aerial
and igneous particles manifest themselves with very
intense heat. With regard to the heat of quicklime,
the learned Willis has maintained in his treatise on
Fermentation that in consequence of the long-con-
tinued calcination of the calcareous stone, igneous

154 Mayow

particles are fixed in it and are firmly detained in its
structure which is even harder after calcination than
before, and that afterwards these particles, driven
out of their quarters by the water poured on the lime^
burst forth and by their motion produce heat. But
indeed it seems to me scarcely probable that igneous
particles are fixed in quicklime in this way, for its
structure seems to be too loose to detain the extremely
agile nitro-aerial particles. But even supposing igneous
particles to exist in quicklime, how should the pouring
of water upon it rouse them to the motion requisite
for heat ? For aqueous particles are of a nature to
arrest the motion of igneous particles and to extinguish
them, but not to throw them into motion.

Wherefore we are ^t liberty to suppose that nitro-
aerial and igneous particles exist in quicklime, not
simply and by themselves, but closely combined
with some salt, and that the heat which arises when
water is sprinkled upon it is due to the existence in
it of contrary salts — an acid, to wit, and an alkali —
and to their action upon each other.

For, first, we must hold that a fixed salt is contained
in quicklime. For if quicklime is thrown upon an
acid liquid, such as water with which oil of vitriol has
been mixed, the water will presently be deprived of all
its acidity, since the fixed salt of the lime immediately
absorbs and destroys the acid salt of the vitriol, being
contrary to it.

Further, if spirit of vitriol be poured upon quick-
lime slaked by pouring water on it and not yet quite
dry, heat and a pretty brisk fermentation will result
from their action upon each other — a clear proof that
an alkaline salt exists in quicklime. For in this case
the heat in the previously slaked lime does not arise
from the moisture of the vitriolic spirit but from the

I

On Sal Nitriim and Nitro- Aerial Spirit 155

effervescence of its acid salt with the fixed salt of the
lime.

Further, common sulphur, boiled in the water in
which quicklime has been slaked, will dissolve exactly
as it would in a liquid imbued with an alkaline salt.
However, if spirit of vitriol or any acid liquid be
poured into the solution, the sulphur will at once be
precipitated with a fetid smell ; so that it is certainly
established that the solution of sulphur in the water
in which quicklime has been slaked, is due to its
alkaline salt, for otherwise the sulphur would not be
precipitated from that water when acid liquids are
poured into it.

To this I further add that if quicklime be put into a
solution of sal armoniac, whatever of acid there is in
the sal armoniac will be absorbed by the fixed salt of
the lime, while the volatile sal armoniac, liberated
from the saline fetters, passes meanwhile into vapours^
just as if fixed salt of tartar had been mixed with the
sal armoniac. Now all these things clearly prove
that quicklime and the water in which it has been
slaked are impregnated with a fixed salt ; and this
we may see for ourselves, for it is certain from common
observation that an alkaline salt, or at least a nitrous
salt partly composed of an alkali, exudes from walls
which have been recently whitewashed and adheres
to them.

Further, the existence of acid salt in lime may be
inferred from what follows. For if a solution of any
fixed salt be mixed with the water of quicklime, pre-
cipitation will immediately take place and the water
will become milky, which would not, however, happen
unless that water were imbued with some acid salt.
Besides, the water of quicklime poured upon any
volatile salt fixes it and changes it into an insoluble

156 Mayow

lime, as was observed by the learned Zwelfer. But it
is well enough known that volatile salts are not fixed
or changed in that manner except by an acid salt.
Further, if water which has slaked quicklime be
poured copiously into boiled milk, the milk will soon be
curdled, just as if an acid liquid had been mixed with it.

From what has been said, it is evident I think that
contrary salts lie hidden in lime, as may also be
inferred from the very contexture of slaked lime. For
whenever contrary salts in their encounter lay hold of
any third matter, there is formed from the close
combination of all a neutral body which is quite
insipid, like terra damnata^ and altogether insoluble
in water. Of this sort are nearly all the Magisteries,
such as those of hartshorn, of coral, and the like. Nor
does slaked lime seem to be anything but a Magistery
formed by a union of contrary salts with a stony earth.
Indeed if salt of tartar be mixed with a solution of
alum, a tertium quid \n\\{ be formed that is somewhat
sweet and astringent to the taste and not very different
from lime, so that it is not at all wonderful that an
alkali, pure and unmixed, is not drawn out from
quicklime by pouring water upon it ; for its contrary
salts act on each other when water is poured on it
and are turned into a neutral body. But since the
acid salt of the lime is not united firmly to the fixed
salt, as will be shown below, the fixed salt extricates
itself in the course of time from the fetters of the
acid salt and at last, thrust from the structure of the
lime, adheres to the whitewashed walls.

We notice, lastly, here, in support of the foregoing,
that quicklime will not become warm if sprinkled with
highly rectified spirit of wine, or spirit of turpentine,
or with other liquids of that kind. And the reason
seems to be that spirit of wine and liquids of that

On Sal Nitrtim and Nitro- Aerial Spirit 157

sort, abounding in volatile sulphur, are quite in-
capable of dissolving fixed salts, so that neither can
the alkaline salt of quicklime be dissolved by them,
and yet this is an indispensable condition of the
production of heat in lime, as will be shown later.
So that it is abundantly clear that the heat of quick-
lime is not, as is commonly supposed, produced by the
igneous particles which are simply fixed in it, being
thrown, at last, into vigorous motion by the humidity
which is antagonistic to them, but by the liberation
and effervescence of its salts ; inasmuch as quicklime
does not become hot when moistened by any liquid
indiscriminately, but only by such as are fitted for
speedily dissolving its salts. Nay, the liquids which,
in consequence of abounding in volatile sulphur, are
best adapted to set igneous particles in motion and
produce heat, when poured on quicklime produce no
heat in it, although, on the other hand, the same lime
becomes very hot when sprinkled with aqueous fluids,
the chief extinguishers of fire and heat. But this can
result from no other cause than the fitness of the
latter, but not of the former, liquids to dissolve its
salts.

It remains now to inquire whence these different
salts of lime trace their descent. In the first place,
then, with respect to the origin of the fixed salt, it is
generated in the same way as in earth. For as the
seeds of fixed salts lie hidden in the earth's bosom, as
was elsewhere shown, so too, they may be found in
shells, chalk, and stones ; and the-proof of this is that
most of these effervesce with any acid spirit poured
upon them.

As regards the origin of the acid salt of quicklime,
we must believe that it is made by the action of
nitro-aerial and igneous particles during the long

158 Mayow

calcination of the calcareous stone. For as the acid
spirit of sulphur is produced from the more fixed par-
ticles of common sulphur, also the spirits of vitriol and
of nitre from metallic or earthy sulphur, by the action
of nitro-aerial and igneous spirit, as I have before
attempted to show, so it is likely that the nitro-aerial
particles of fire encounter, in the course of the long-
continued calcination of the calcareous stone, the more
fixed particles of the sulphur of the stone (for cal-
careous stone, like flints, contains much sulphur), and
rub and sharpen them, and at last convert them into
an acid salt in the manner described above.

Let us see next how it is that contrary salts — acid,
to wit, and alkali — subsist together in quicklime and
yet do not act upon each other until water is poured
on the lime. As regards this, it is probable that the
acid spirit of quicklime becomes so sharp and fiery in
consequence of its long calcination, as to be altogether
unfit for engaging with fixed salts until its more
powerful igneous force is diluted by admixture with
water and to some extent moderated ; for saline
solvents are sometimes so corrosive that they fail to
dissolve or in any way affect metals, which in their
nature closely resemble fixed salts, till their too keen
force is diminished by admixture of water.

Further, the fixed, like the acid, salt of the quick-
lime becomes in the highest degree biting and fiery
by reason of the fiery particles infixed in it during
its long calcination. For it is to be noted that
although nitro-aerial and igneous particles are of a
saline nature, still they are opposed neither to acid salt
nor to alkali, but, on the contrary, when combined
with either, increase its power and render it fiery. But
since nitro-aerial particles are fixed in dense number
in the acid, and in the fixed, salt of lime, it comes to

On Sal NitriLm and Nitro- Aerial Spirit 159

pass that these contrary salts are kept apart and, as it
were, reconciled by the mediation of the nitro-aerial
particles which are in harmony with both, so that
they are unable mutually to attack or act upon each
other. But when these salts are diluted with water,
they lay aside, at least to some extent, their fiery
particles and become less acrid, as will be apparent
if fixed salts exposed to a hot fire are afterwards dis-
solved in water ; for then the salts which the fire has
made extremely acrid and caustic will lay aside their
acridity and return to their original state. Hence
it is that the contrary salts of lime, after they have
been dissolved in water, are then fit for acting upon
each other and for mutual effervescence.

And in this we have an explanation of the fact that
quicklime does not become hot when sprinkled with
spirit of wine or other sulphureous liquids of that sort,
as has been said before. For since such liquids are
incapable of dissolving the fixed salt of the lime, they
cannot temper its too acrid and fiery force ; yet this
is absolutely necessary for producing its heat.

I add, lastly, that the acid salt of the lime seems to
contract a somewhat dry nature on account of the
very dry and solid nitro-aerial particles densely fixed
in it ; whence it is that that acid spirit can remain so
long in the hottest fire. For the extremely solid
nitro-aerial particles, densely fixed in the acid salt,
make it somewhat rigid, so that its particles cannot
be carried aloft by any force of fire. And hence it
is that that acid salt of lime, being of a drier nature,
will not engage with its fixed salt until it has been
dissolved by pouring water upon it.

But yet another difficulty is here presented. For
admitting that contrary salts exist in Hme and in the
water in which it has been slaked, how does it

i6o Mayow

happen that these opposing salts, even after they have
acted upon each other, should reside in the said water
with their strength almost unimpaired ? For neither
is utterly destroyed, but each of the two performs the
operations appropriate to its nature, as was shown
above ; while yet in other cases when opposite salts
are mixed, either both succumb, after a struggle in
which each engages with equal strength, or one of
them gains the mastery while the other is completely
conquered.

In regard to this, it is probable that although in the
lime and in the water in which it is slaked, the acid salt
and the fixed salt combined together are changed into
some neutral substance, yet the acid salt and the fixed
salt are of such a kind as to be by no means fit for
mutually subjugating themselves and destroying their
powers. But to make this more intelligible, it will be
of advantage, I think, to premise some brief observa-
tions on the combination of contrary salts with each
other and with other substances.

OF THE COMBINA TION OF CONTRARY SALTS, AND
PRE CI PITA TION

In the first place, then, it is to be noticed that
although acid salts and alkalies pass into a neutral
substance when they meet, yet they do not, as is
generally supposed, entirely destroy each other. For
example, when the acid spirit of salt is coagulated with
a volatile salt (and the same explanation applies to
sal alkali), although the mixed salts seem to be
destroyed, yet they may be separated from each
other with their forces unimpaired, as takes place
when sal armoniac (or any volatile salt combined with
an acid spirit) is distilled with salt of tartar. For in
this case whatever of acid there is in the sal armoniac

On Sal Nitrum and Nitro- Aerial Spirit i6i

will be coagulated with the fixed salt of tartar, but the
volatile salt, of which it also in part consists, ascends
of the same nature as before. And the reason of this
is, that the acid spirit of salt is capable of entering
into closer union with any fixed salt than it is with
a volatile salt, so that it immediately leaves the volatile
salts that it may be combined more intimately with
the fixed salt. But if oil of vitriol is united with salt of
tartar, they can scarcely be separated from each other.
And yet this is not because these salts have mutually
destroyed each other, but because there is nothing in
nature with which either of them can unite more
firmly than they do with each other.

As acid salts leave volatile salts to form a closer
union with the fixed salt of tartar, as being a more
suitable partner, so doubtless fixed salts select some
one acid in preference to others that they may com-
bine with it in a closer union.

But to illustrate this by an example : if oil of vitriol
is poured upon nitre, which consists of an alkaline
and of a volatile acid salt (as was shown above), the
fixed salt of the nitre will soon leave its own acid and
will enter into union with the acid of the vitriol, which
is more concordant with it ; so that nitrous acid,
on account of the mixture with the vitriolic acid, is
correctly said to be precipitated from the embraces of
the alkaline salt. That the case is so, is clear, for
if nitre mixed with oil of vitriol be distilled, the
spirit or acid salt of the nitre will pass under a mild
heat into the receiving vessel, while yet in other
circumstances that spirit will not be carried up except
by a very vehement fire. No doubt it is because the
volatile acid salt of the nitre has been expelled from
the society of the alkaline salt by the more fixed
vitriolic acid that the acid of nitre, now liberated from

L

1 62 Mayow

union with the alkaline salt, ascends under a heat no
greater than is required for the rectification of the
spirit of nitre ; while in other circumstances the
same spirit of nitre is sundered only with difficulty
from its union with fixed salt, and requires a very
intense heat for its distillation.

It is a corroboration of this view that the mass left
in the retort after a distillation of this kind, closely
resembles vitriolated tartar, and can be properly sub-
stituted for it. For since the alkaline salt of which
nitre is in part composed, differs scarcely at all from
salt of tartar, a union of that salt with oil of vitriol
will produce an acido-saline salt, differing not much
from vitriolated tartar.

Nor is it mutually among themselves only that
salts strive after union, but also with other things ; and
from them they part so as to combine with a salt
more concordant with themselves. For example, any
acid spirit at once attacks metals and combines with
them to form vitriol. But if salt of tartar be poured
upon these vitriols dissolved in water, the acid salt of
the vitriols immediately combines with the salt of tartar,
and the metal, freed from the fetters of the acid salt,
will fall headlong to the bottom.

As an acid salt combines with metals, so also does
an alkaline salt with sulphur. If, however, an alkaline
salt in union with sulphur be dissolved in water, and
then any acid spirit be poured into the solution, the
fixed salt will instantly rush into union with the
acid salt ; and the sulphur, meanwhile, liberated from
its union with the fixed salt, and rising in aerial form,
will indicate its presence by its fetid odour — as
happens when sulphur dissolved in lye is precipitated
by the addition of an acid liquid.

Nor is it with an alkali only but also with the

I

On Sal Nitrum and Nitro- Aerial Spirit 163

metals allied to it that sulphur seeks for union ; yet
in such wise that the metals, like the alkaline salt,
will at once leave it to form a more intimate union
with an acid poured upon it. For if an acid liquid
such as aqua fortis be poured upon a metal rich in
sulphur, say antimony, and then the mixture be
heated, the sulphur will be sublimed to a considerable
extent, since the acid salt of the liquid uniting with
the metal expels its sulphur from its lodgment.

Lastly, as metals leave their own sulphur that they
may combine with an acid salt, so sulphur will quit
metals with which it is united, to coalesce in a closer
union with a fixed salt. For if a metal abounding in
sulphur, such as stibium^ be boiled in strong lye, the
metallic sulphur will dissolve in it, since the sulphur
seeks to be united with the fixed salt of the lye rather
than with the metal ; but this metallic sulphur will be
precipitated also from the fixed salt, if an acid salt is
poured upon ^t.

It is also to be noticed here that although sulphur,
like an acid salt, can combine with an alkaline salt
and with metals, and can be precipitated from them,
we must not therefore suppose that a certain acid
salt (such as the Oleum Sulphiiris per Catnpanam)
lies hidden in a mass of sulphur, and that by its
intervention the alkaline salt unites with the sulphur.
For if alkaline salt and sulphur united together (as
in liver of sulphur) be dissolved in water, and the
acid oil of sulphur be then added, the sulphur im-
mediately thrust out from its union with the fixed
salt will be precipitated. And yet, if the combina-
tion of the sulphur with the fixed salt resulted from
this, namely, that the acid salt contained in the sulphur
unites with the alkaline salt, then the pouring of that
acid or oil of sulphur upon them when combined with

164 Mayow

each other would by no means separate them from
each other. Nay, if such an acid existed in sulphur,
it would hinder altogether the union of the sulphur
and the alkaline salt ; since all acids (but especially
one so corrosive as oil of sulphur) have the power of
separating sulphur from fixed salt and precipitating it.
I further remark that acid salts do not combine with
alkaline salt or even with metals, without effervescence
and a notable degree of heat. But such is not the
case when sulphur combines with either of them ; so
that clearly the combination of sulphur with fixed salt
would appear to result not so much from any
antagonism as from their mutual affinity, as has
already been shown in some detail.

I may here further^ remark, by the way, that salts
of different kinds should not without the greatest
caution be compounded together in the same medicine,
lest one of them should entirely destroy the efficacy of
another, and even change it into something quite
difTerent from what it was at first. For example,
when obstructions or a diminished fermentation of the
blood, point to the use of steel, it seems to me
inadvisable to mix the salt of wormwood or any
lixivial salt with the vitriol of Mars or with the
aperitive Crocus Martis. For when that medicine
dissolves in the stomach, the acid salt which the
vitriol of Mars contains will immediately unite with
the lixivial salt, and meanwhile the metaUic part of the
vitriol, driven out from its acid fellowship of the salt,
will be precipitated as Colcothar or astringent Crocus
Martis^ which is by no means aperitive. For the case
will be very much as if the acid salt of the said vitriol
were expelled by fire, when nothing metallic will be
left but Colcothar or astringent Crocus Martis. And
indeed the lixivial salt also mixed with the said vitriol.

i

I

On Sal JVitnim and Nitro-A'erial Spirit 165

will acquire a quite new nature because of the addition
to it of the acid salt of the vitriol.

But now to adapt the foregoing to the subject
in hand, it is seen that in quicklime and the water in
which it has been slaked, the contrary salts are of a
nature little suited to combine very closely with each
other, and the proof of this is that either of them
will immediately unite with a salt more suitable for
it.

For first it is manifest that the acid salt of lime
separates from the fixed salt with which it was united,
that it may be more firmly combined with the salt of
tartar. For if salt of tartar be mixed with water in
which quicklime has been slaked, precipitation takes
place at once and the water becomes turbid and milky.
And the reason is, that although the acid salt of the
lime is to some extent subdued by its partner the
fixed salt, yet its powers are not so completely
destroyed but that the acid is still able to dissolve a
small portion of limestone, and besides to fix volatile
salts as acids do. If, however, salt of tartar be mixed
with the aforesaid water, the acid salt of the lime will
combine most closely with it as being a more suitable
partner, and their strengths will be utterly destroyed
by each other; so that the limestone can now no
longer be dissolved by the destroyed acid of the lime,
but is precipitated to the bottom along with these
combined salts.

And for the same reason the alkaline, or rather the
fiery volatile salt of the lime, will at once desert its
acid partner to which it is united, in order to form a
closer union with the acid spirit of vitriol, which is
more suitable for it. For if sulphur be dissolved in
water in which lime has been slaked and spirit of
vitriol be then added to the solution, the sulphur will

1 66 Mayow

presently be precipitated with fetid odour. For
although already in the slaking of the lime the
alHaline salt of the lime has united with its acid, not
without effervescence and a quite notable heat, yet it
will nevetheless immediately desert the acid betrothed
to it to be married in closer wedlock with the vitriolic
acid, by which however its powers are so completely
overcome that the alkaline salt of the lime combined
with the vitriolic acid is no longer able as before to
dissolve sulphur ; but that a fixed salt is combined
with an acid salt in the water in which quicklime has
been slaked, and further that the heat of that water is
caused by the union of contrary salts, will be made
still clearer by what is to be said below.

Since the contrary salts in the water in which
quicklime has been slaked are but little fit for entering
into a very close union and for mutually destroying
each others powers, each of them consequently can
perform the operations appropriate to its own nature.
And this is seen clearly in sal armoniac, in which the
acid salt is combined with a volatile salt, and yet that
acid salt is not so completely subdued by its unequal
adversary, the volatile salt united with it, as to be
unable to dissolve iron as acids do and to change it
into vitriol. Yet if any fixed salt contends with the
acid armoniac salt, then indeed its strength is com-
pletely destroyed so that it is quite incapable of dis-
solving iron any longer. And the case in fact seems
to be similar in water of quicklime, for here the less
opposing salts do not so completely destroy each
other but that either of them can act according to its
nature. For the fixed salt of that water is able to
dissolve sulphur, and its acid salt can fix and destroy
volatile salts, as was said above.

With respect to water which has slaked quicklime,

On Sal Nitrunt and Nitro-Aerial Spirit 167

we note further that oil of vitriol, when put into it,
does not produce in it effervescence, or precipitation,
or any degree of heat. And yet it is certain that the
acid salt of vitriol unites with the fixed salt of the
lime. For if spirit of vitriol be poured into a solution
of sulphur made in water that has slaked quicklime, the
sulphur will be immediately precipitated, as we have
already remarked. And yet this would certainly not
happen unless the acid of the vitriol uniting with the
fixed salt of the lime drove the sulphur from its
lodgment.

But to make the reason of this clear, it should be
noted that if salts which are somewhat saturated and
weakened by their opposites, afterwards meet a salt
that is still more repugnant, there will yet be no
effervescence or heat from their mutual action as there
would be in other circumstances. For example, if oil
of vitriol be united with any metal whatever with a
distinct ebullition (as is the case when iron is
dissolved in oil of vitriol) and then fixed salt of tartar
is put into that solution, although the acid spirit of
the vitriol combines with the salt of tartar, and the
metal now liberated from the acid salt is precipitated,
still no ebullition or heat will be produced in so far as
the acid spirit of the vitriol was previously to some
extent saturated by the metal joined to it. And the
same thing also happens when salt of tartar is mixed
with a solution of sal armoniac. For when this is
done the salt of tartar absorbs, without any ebullition,
whatever acid there is in the sal armoniac.

And for a perfectly similar reason the alkaline salt
of the water in which quicklime has been slaked unites
without any effervescence with oil of vitriol poured
into it, because the alkaline salt of the lime has been
previously saturated with its own acid. Consequently

1 68 Mayow

that the water in which quicklime has been slaked is
impregnated with contrary salts and these combined
with each other, is clearly evidenced by the fact that
the alkaline salt of that water unites with any acid
salt whatever, and its acid salt with volatile salt,
without any effervescence or heat.

But further, that the precipitation may be seen in
any liquid and that the liquid may become turbid, it
is indispensably necessary that what is precipitated
should be opaque and not transparent, in order that
as it descends it may fill the pores of the liquid and so
hinder rays of light from being transmitted through
them, as happens in the precipitation of iron or of any
other metal. For when iron dissolved by an acid
liquid is driven from its embraces, it is no longer
transparent but resumes its previous state, namely,
that of a solid and opaque body, so that the iron, as
it goes down, obstructs the pores of the liquid and
renders it turbid.

But if that which is precipitated be nowise opaque,
but transparent or soluble in the liquid, then the
liquid in which the precipitation takes place will be-
come in noway turbid. Hence when oil of tartar /^r
deliquium is mixed with a solution of sal armoniac,
although the fixed salt of tartar absorbs the acid of
the sal armoniac and the volatile armoniac salt is
precipitated from its union with its partner, still the
liquid does not become in the least turbid, because
that volatile salt, in the course of its descent, dissolves
in the liquid and does not at all obstruct its pores.
Similarly, when an acid salt is precipitated from its
union with a fixed salt by the addition of a more
appropriate acid (as happens when the alkali of which
nitre partly consists leaves the nitrous acid and com-
bines with oil of vitriol poured upon it, or also when

On Sal Nitrtim and Nitro- Aerial Spirit 169

the alkaline salt of quicklime leaves its own acid and
combines with the acid of vitriol), although the acid
salt is first precipitated from the embrace of the
alkaline salt, still the liquid does not become in the
least degree turbid, because that acid salt which sinks
is in nowise opaque but soluble in the liquid, and
consequently transparent and imperceptible.

Nor should we omit to state that quicklime mixed
with the lye of ashes renders it more powerful and
acrid. And yet in water which has slaked lime the
acid salt, which is entirely opposed to the lixivial salt,
seems to have the upper hand, since precipitation will
take place in that water if an alkaline salt is put into
it, as was said before.

In regard to this it is probable that the aqueous
part of the lye, when poured upon quicklime, no
sooner meets the very fiery and dry acid salt of the
lime and renders it fit as it were for dissolving, so that
it effervesces with the alkaline salt (for it was shown
above that the acid of lime does not, unless diluted
with water, effervesce with an opposite salt), than
the alkaline salt with which the lye is imbued com-
bines at once with the acid salt of the lime and so
destroys its powers that the alkaline salt which
belongs to the lime is not now, as in other cases,
conquered and subjugated by the acid of the lime, but
may be extracted from the water of the lye with its
powers unimpaired. Since, therefore, the alkaline salt
of quicklime is extremely acrid and fiery, it necessarily
follows that the lixivial water impregnated with it
becomes in the highest degree biting, caustic, and
fiery.

I

1 7o Mayow

CHAPTER XV

OF THE THERMAL WA TERS OF BA TH.
INCIDENTALLY, OF THE SOURCE OF SPRINGS

Among the most famous thermal waters are to be
reckoned those of Bath, for in these wonderful waters
there dwells perpetually a vestal and sacred fire — a
friendly treaty being as it were formed between
elements the most discordant.

Before coming to the question of how these springs
are warmed, it will be of advantage, I think, to make a
brief inquiry into the ingredients of their waters.

In the first place, then, it is evident that the Bath
thermal waters are impregnated with a salt of an acid
nature ; for if any alkaline or purely volatile salt is
mixed with their waters, a precipitation will
immediately be produced in them, and they will
become turbid and milky. Further, warmed milk will
be coagulated if the water of these thermal springs is
poured into it, precisely as if any acid liquid were
used.

And yet the salt of the springs does not appear to
be acid pure and simple, but combined with some
alkaline salt : for if that water be evaporated to
dryness, a salt of a more fixed nature will be found at
the bottom of the vessel, since it effervesces if any
acid spirit is poured on it. Of this nature, too, are the
mud and sand of the springs which are thrown out
along with the bubbling stream of water, for if any
acid liquid is poured upon them, a marked ebullition
will immediately be produced. It is also to be
observed that a salt in these waters, or rather a limy

071 Sal Nitrtim and Nitro-Aerial Spirit 171

earth, adheres almost everywhere to the bottom of
the channels by which the waters are carried off.

From what has been said, it may be inferred that
the thermal waters of Bath are impregnated with a
certain acido-saline salt. And indeed this salt of the
thermal waters does not seem to be very unlike
vitriolated tartar or aluminous salt. But the reason
why these salts do not destroy each other, but that
each of them effervesces with a salt opposed to it, will
be to some extent intelligible from what was said in
the previous chapter. For the said salts are so
imperfect that they are not able to destroy each other
entirely when they combine together. But there will
be a fuller discussion of these salts afterwards.

As for nitre and sulphur, with which it has been
hitherto supposed that the Bath thermal waters are
impregnated, I think that neither of them exists
dissolved in the water of these springs.

That nitre does not exist in them is evident,
because if the salts which remain after evaporating
the water of the baths are placed on burning charcoal,
they in nowise deflagrate like nitre. However, I
will not deny that the immature salts of an alkaline
nature (with which the mud and sand of the baths are
imbued) may, perhaps, if exposed for some time to the
air, be changed by its influence into nitre.

As to sulphur, which is so often said to be present
in nearly all thermal springs, my opinion is that it
does not exist dissolved in these waters. For if a
solution of alum, or of vitriol, or any other salt,
whether acid or fixed, is mixed with the water of
these thermal springs, the precipitation of sulphur is
not at all indicated either by a fetid odour or by any
other sign. And yet that always happens in solution
of sulphur made in the water in which quicklime has

172 Mayow

been slaked, or in lye, when the sulphur is precipi-
tated from them by the addition of any acid liquid.

I am aware that the water of these thermal springs
immediately becomes white if salt of tartar, or a
simply saline volatile salt, be put into it, as was
already remarked. But this white colour is caused by
the precipitation not of sulphur but of a certain
stony or aluminous matter, just as happens to water
which has slaked quicklime when any fixed salt is
mixed with it, though it is not to be supposed that
sulphur is dissolved in it. For if sulphur were boiled
in the water in which quicklime has been slaked, the
water would not become white, as before, on the
addition of fixed salt, but would do so on the addition
of acid. So that fixed salts appear manifestly to be
fitted for dissolving sulphur but not for precipitating
it. Wherefore if the waters of the thermal springs
were imbued with sulphur, they would not be
precipitated as they are by a simply saline salt but by
an acid. And indeed the sulphur precipitated by
them would manifest itself by a fetid odour, but this
does not at all happen.

I further add that some acid or aluminous salt
seems to preponderate in these thermal waters, so
that they are quite incapable of dissolving sulphur.
Nay, if common sulphur be boiled in the said
waters, these waters will not be at all tinged with
the yellow colour of sulphur, nor can sulphur be
precipitated in any way from the said decoction, as I
have found by repeated trials. And indeed I am
greatly surprised that the distinguished Willis in his
Treatise on the Heat of the Blood, has asserted
that sulphur can be dissolved when boiled in the
water of the said thermal springs, just as in water that
has slaked quicklime. But if sulphur ever appears to

On Sal Nitrum and Nitro- Aerial Spirit 173

be dissolved in the said waters, I think the source of
the error Ues in the fact that the decoction was made
in a vessel, used for such purposes, in which perhaps
at some time a fixed salt had been boiled ; so that the
solution of the sulphur might be caused by a small
portion of the fixed salt with which the vessel was
imbued.

It is generally believed that if silver be immersed in
the hot Bath waters it will receive a yellow tinge, just
as if it were put into a solution of sulphur ; and hence
the common belief that these thermal waters are
impregnated with sulphur ; but the contrary of this
has been ascertained by experiment. For silver put in
the baths does not become at all red or yellow, but
rather black. But the error seems to arise from this,
that the keepers of the baths are in the habit of
tinging and as it were gilding silver coins with a
saline-sulphureous mud such as is found everywhere
in sewers, and then selling them for a small sum to
visitors, as coins coloured by the waters of the baths.

It should also be noticed here that a certain
bituminous mud and a small quantity of common
sulphur are usually thrown out along with the gush-
ing waters of the thermal springs ; yet these eithe
float on the surface of the waters or lie at the bottom,
but are in nowise dissolved in the said waters.

Nor are the said thermal waters impregnated with
armoniac salt, as some have supposed ; for if salt of
tartar is put into a solution of sal armoniac, the simply
saline volatile salt (of which sal armoniac partly
consists), released from the fetters of the acid salt with
which it was previously united, will instantly rise in
vapours and will soon betray its presence by assailing
the nostrils which approach it. But this in noway
happens with the thermal waters.

1 74 Mayoiv

Lastly, as regards vitriol, the bath usually called the
Cross Bath, and also the one named the Hot Bath,
appear to contain no vitriol whatever. For if pounded
gall-nuts are infused in the waters of the said baths,
the waters will by no means assume a purple or a
black colour, and yet this would certainly be the case
if these waters were imbued with vitriol. With
respect to the so-called King's Bath, it seems to be
impregnated with a little vitriol ; for if pounded gall-
nuts are put into its water, it will be slightly tinged
with a blackish-purple.

But it should be noted that along with the gushing
waters of the said hot springs, there rushes out from
the earth a mineral of a metallic nature which can
easily be changed into vitriol. For if any acid liquid
is poured on the san^ which escapes from the earth
along with the water of the hot springs and is found
at the bottom of the baths, this sand, when corroded
with considerable effervescence by the acid menstruum,
will in part be turned into vitriol, just as iron filings
are when corroded by an acid liquid. For if that
sand of the baths, when impregnated with an acid
liquid, be added to an infusion of galls, the liquid will
at once acquire a dark purple colour ; while, on the
other hand, if the infusion of galls be poured upon
the sand when taken fresh from the baths (but not
yet corroded by an acid liquid), it will not become
purple at all — undoubtedly a clear proof that the
metallic sand of the baths assumes the vitriolic nature
only when corroded by an acid menstruum. It is to
be noticed also that this sand of the hot springs will
spontaneously change into vitriol if kept for a con-
siderable time and exposed to the air ; for if such
sand is put into an infusion of galls, the water will at
once take a dark purple colour. Nay, if it be put on

Oil Sal Nitrum and Nitro- Aerial Spirit 175

the tongue, the taste of vitriol will be manifest
enough. Indeed nitro-aerial spirit, after a lapse of
time, unites and effervesces with the metallic mineral
or saline-sulphureous marchasite (such as vitriol is
usually made from) which is mixed in the said sand,
and at last turns it into vitriol in the manner
described in another place.

Let us next consider how not only the hot springs
of Bath but all thermal springs acquire their heat.
With regard to the heat of thermal springs, I cannot
agree with those who maintain that their heat is due
to warmth communicated by subterranean fire. For
if any fire of this sort burned in the bowels of the
earth, it would certainly betray itself by its flame
bursting out somewhere ; since indeed a continual
influx of air is absolutely necessary for the mainten-
ance of fire. But granting that there are subterranean
fires, how is it, I ask, that they are not extinguished
by the waters which they are supposed to heat ?
And whence should the material be supplied for
maintaining a fire so vast and enduring ?

Wherefore, since it is not probable that the hot
springs are heated by subterranean fires, we may
maintain with our learned countryman, Jordan, that
the warming of the hot springs originates in
fermentation excited somewhere in the bowels of the
earth. But to understand how this fermentation is
produced the following must be premised.

In the first place, then, it may reasonably be
supposed that at any rate most fountains derive their
origin from rain-water. For it is not probable that
any o f them are derived, as is generally believed,
from the sea ; for who can entertain the idea that the
gushing waters which burst forth from the summits
of the loftiest mountains have their origin in the

176 Mayow

depths of the sea ? For it is by no means to be
beheved that sea-water ascends by filtration to the
tops of mountains ; for in whatever way any liquid
may rise up through a filter, yet it will not flow out
of the filter unless its other end is at a lower level
than the liquid ; and consequently sea-water obviously
cannot gush out by means of filtration from places at
a higher level than the ocean itself.

Whether sea-water, which, in consequence of being
impregnated with salt, is heavier than spring-water,
is comparatively so much heavier as to force
spring-water to the tops of lofty mountains, as the
ingenious Dr R. Hooke has suggested, I will not
definitely say ; yet it can scarcely be thought that any
springs are due to this cause. For if any had their
source in the sea, how are we to explain that most
fountains follow the temperature of the air and almost
fail in very warm weather, or also in frost ? Should
any one say that the aqueous particles are by reason
of the greater heat converted into vapours and ascend,
and that therefore the springs dry up in summer, I
ask, how is it then that fountains are diminished when
the earth outside is so bound by frost that the passage
for vapours is entirely closed ?

I think, then, that it should be held that at least the
majority of springs have their origin in rain-water.
And yet I would not be understood as supposing that
rain-water is stored in certain subterranean caverns,
as it were in special cisterns, whence it flows out into
springs. For such a supposition is unnecessary when
the thing can be otherwise explained. Now since
the surface of the earth is like a sponge or filter, it can
absorb rain-water in quantity suflScient to form
springs that will endure for a long time. For we
observe that the outer crust of the earth is always

On Sal Nitrum and Nitro- Aerial Spirit 177

steeped in a sort of moisture to the depth of several
feet, and that aqueous particles escape from it only
very slowly. And hence it is that the ground
wet with showers can be dried up only after a long
time. It corroborates this view that if a pair of cuts,
several feet deep and of sufficient length, are dug in
almost any soil so that they meet at their lowest part,
the drops of waterflowing here and there from the banks
and uniting at last at the bottom, will make an artificial
spring or rather rivulet. And this shows why it is that
spring-waters well forth with greater or less abundance
according as the weather has been wet or dry. Now
this would by no means be the case if springs were
derived from the sea and not from the air.

Further, it must, I think, be granted that nearly all
the mountains in every part of the world consist
of saline-sulphureous matters such as vitriolic or
aluminous marchasites and the like.

I remark, in the last place, that if saline-sulphureous
earth of this sort be wetted with rain-water it will
effervesce and grow warm. For if marchasites or
saline-sulphureous masses, such as vitriolic and similar
salts are produced from, be exposed to moist air and
rainy weather they will soon effervesce markedly.
Nay, if any saline-sulphureous mineral, recently dug
up, is wetted with rain-water it will after a short time
effervesce and grow warm.

Let us next inquire why saline-sulphureous minerals
of this sort effervesce when wetted with rain-water,
for it is to be supposed that the heat of the thermal
springs results from the same cause. And we may
indeed suppose that the aerial particles which are
mingled with almost all water, but especially with
rain-water, contribute in no small degree to produce
the said effervescence. For that air is mixed with

M

17? Mayow

aqueous particles has been placed beyond all doubt
by Boyle's experiments ; for if spring or rain-water
be put in a glass from which the air is exhausted by
suction, innumerable little bubbles, formed of the
substance of air, will burst from it. In fact, as soon
as the pressure of the atmosphere is almost removed,
the aerial particles dispersed through the mass of the
water immediately open and stretch out in virtue of
their elastic force ; so that the little portions of air
which previously lay hidden and quite inconspicuous
in the pores of the water, now swell into little bubbles
which are forced upwards on account of their lightness.
Moreover, that air resides in the small pores of water
will be further proved by the following experiment.
For let a small glass be placed in such a way under
water contained in a suitable vessel, that all the air
may escape from it and water enter in its place.
Then let that glass, filled with water, be inverted and
placed at the bottom of the said vessel, and let it
remain so, much as in Plate V., Fig. 3. After these
preparations, let the vessel into which the inverted
glass is put be placed on the fire so that the water
contained in it may be heated, and then let the vessel
be removed from the fire so that the water may again
cool. When this is done, we shall find that the top
of the inverted glass is occupied by a kind of air
partly composed of the vapours raised from the
boiled water and not yet completely condensed, but
partly of aerial matter. For since the air mixed with
the water contained in the glass is rarefied by the
heat of the fire, and consequently occupies more space
than formerly, it is raised in the form of little bubbles
to the top of the glass by the pressure of the
surrounding water. And that this aerial matter is in
part air, I infer also from this, that a certain portion

On Sal Nitrum and Nitro- Aerial Spirit 179

of it will never condense into a liquid. It possesses,
moreover, as much elastic force as ordinary air, as I
have ascertained by the method elsewhere described.

To this I add, lastly, that air interspersed in water
is drawn in by fishes for respiratory purposes. And
indeed the gills with which fishes are endowed seem
to be formed for this very end, that air (which is ab-
solutely necessary for animal life) may be separated
from the water by their action and mixed most
intimately with the mass of the blood. And the
reason that fishes are always engaged in alternately
drawing in and expelling water, as terrestrial animals
do common air, is that something aerial which is
necessary to life may be separated from the water, as
in the other case from the air, and passed into the
mass of the blood.

It corroborates this view that most fishes possess a
swimming-bladder filled with air. For there can be
no doubt that fishes draw this air from the pores of
the water. Let me say also in passing that if a fish is
placed in water contained in a suitable vessel from
which the air is exhausted, it will no longer swim on
its belly, but on the contrary on its back. Its belly
will also rise to some extent above the surface of the
water. And the reason seems to be that the air
enclosed in the swimming-bladder expands in virtue
of its elastic force as soon as the pressure of the
external air is withdrawn, so that the said bladder
and also the abdominal cavity in which it lies are
inflated by the air, with the result that these swollen
parts are forced upwards by the pressure of the water
while the back of the fish descends. But if after the
fish has died for want of air, external air is again
admitted into the glass, the fish will immediately sink
to the bottom and its belly will again become flaccid.

i8o Mayow

Whether the air contained in the said bladder can
pass into the mass of the blood and supply fishes wiih
material for respiration I shall not definitely say,
although that such is the case seems to be indicated
by the fact that fishes can live a little longer than
other animals when deprived of air — unless indeed
this should be accounted for by the circumstance that
fishes, owing to the very languid fermentation of their
blood, consume a comparatively small quantity of air,
so that, unlike most animnls, they do not need to
have a perpetual supply of air.

And now, since the air is intermingled so largely
with rain-water, it is probable that a saline-sulphureous
mineral effervesces when wetted with rain-water
because the aerial partiples, which are conducted by
the aqueous panicles, enter deep into a mineral of
that nature and effervesce with its saline-sulphureous
part. For I have already endeavoured to show that
air is possessed of a highly fermentative nature, and
that nearly all heat results from the effervescence of
something aerial with saline-sulphureous particles.
In fact, a saline-sulphureous mineral of this sort
behaves not very differently from the mass of the
blood, the heat of which arises from this, that the
aerial particles conveyed to it by respiration effervesce
conspicuously with its saline-sulphureous particles, as
has been elsewhere pointed out more fully.

With respect to the heat of the thermal waters, I
think it should be held that the aerial panicles which
descend with rain-water into the depths of the earth
and meet there with the saline-sulphureous mineral,
excite in it a very intense effervescence and heat ; and
that springs of water, flowing from the mineral thus
effervescing, constitute the thermal springs.

Further, it may well be supposed that the earth is

On Sal Nitrum and Nitro- Aerial Spirit i8i

penetrated in some places by pores of a kind
suitable for the passage in dense numbers of aerial
particles, and for sucking them in, as it were. For
since the aerial particles, carried to the saline-sul-
phureous mineral and effervescing with it, are swept
away by the streams of water flowing thence, the
result is that the nearest pvarticles of air are forced by
atmospheric pressure into the place of those carried
away, while these also are soon absorbed and followed
by others ; and thus aerial particles come to the
effervescing mineral in a continual stream.

Perhaps the lofty hills, with deep and abrupt
valleys between, which engirdle Bath on all sides,
contribute somewhat to the entrance of aerial particles
into the ground and to the maintenance of the heat
of the thermal waters. For, in consequence of this,
the air thrown back from the hills, and reflected in
various directions in the valleys, strikes forcibly
against the ground and is thrust into it.

It is a further proof of the views set forth, that the
Bath waters contain a saline-sulphureous mineral,
which seems not very unlike those marchasites from
which vitriol is made ; and indeed the sand of the baths,
if exposed for some time to the air, will effervesce and
turn into vitriol. But the reason that the salts of the
said thermal waters are of an acido-saline nature
seems to be, that when the saline-sulphureous mineral
effervesces in the manner already described, some of
the saline particles are brought to a certain fluidity,
as was previously remarked. But these salts, when
thus liquefied, unite with the other salts which are of
an alkaline nature, and from these, combined with
one another, a certain acido-saline salt is composed. It
is, however, only an immature salt, since it is swept
away, while not yet duly fermented nor brought to

1 82 Mayow

proper maturity, by the waters which flow from the
effervescing mineral.

Should any one now ask how any mineral can
possibly suffice for so long-continued a fermentation, I
reply that the earth is imbued in certain places with
a mineral seed, which, like vegetable seed, grows and
reaches maturity ; and that owing to it the waste of
the said mineral is constantly repaired.

Finally, we remark here that nearly all springs
have a certain warmth at their first rise ; and indeed
the heat of spring-water just escaping from the earth
can be quite sensibly felt in winter when the hand is
immersed in it. No doubt the aerial particles which
descend with rain-water into the earth effervesce in an
obscure motion with the saline-sulphureous particles
of which nearly every kind of earth is composed ; and
consequently a certain warmth is produced, on which
the growth of vegetables depends, as has been else-
where shown. And hence it is that spring-waters are
for the most part impregnated with acido-saline salts.
For if salt of tartar is mixed with spring-water, pre-
cipitation usually takes place in it, and, like the
aforesaid thermal waters, it becomes whitish — a clear
proof of the presence in the water of a salt of an acid
nature. And this, too, is the reason that soap does
not mix with spring-water ; for the acid salt bf such
water contends with the fixed salt of the soap, and so
destroys its powers that the sulphureous and oily part
of the soap cannot be dissolved in the spring-water by
the fixed salt, now subdued, but floats on the surface
in accordance with its oily nature. Moreover the acid
salt of spring-water seems to be combined with a
certain alkaline salt, although the latter be immature ;
and therefore it is, that oil of vitriol, when mixed
with this water, produces a kind of effervescence.

SECOND TREATISE

ON RESPIRATION

The lungs are placed in a recess so sacred and hidden
that nature would seem to have specially withdrawn
this part both from the eyes and from the intellect ;
for, beyond the wish, it has not as yet been granted
to any one to fit a window to the breast and redeem
from darkness the profounder secrets of nature. For
of all the parts of the body, the lungs alone, as if
shrinking from observation, cease from their move-
ment and collapse at once on the first entrance of
light and self-revelation. Hence such an ignorance of
Respiration and a sort of holy wonder. Still, let me
draw near to the inmost vitals, and, concerning so
obscure a matter, make at least a guess.

In discussing on Respiration I shall follow the
method pointed out by nature and begin therefore
with inspiration.

Every one knows that when we inspire, air rushes
into the expanded chest and inflates the lungs. But
authorities are not equally agreed as to the cause of
the air rushing in with such vehemence. Some
account for it by a vacuum and an attraction of I
know not what imaginary sort.

183

184 Mayow

Others a^ain suppose that the air about the chest,
pushed forward by its expansion, propels that which is
next it, and this again the next ; and that so the pro-
pulsion goes on, and thus at last the air near the
mouth is driven into the lungs.

But indeed this view assumes that every place is
full and that this immense space cannot admit any
additional air, however little. But there is no reason
for having recourse to this fulness when the thing can
be and ought to be explained otherwise ; for we may
believe that propulsion of that kind cannot take place
in air, as it is a fluid and easily moved. But this will
be made clearer by the fullowing experiment. For
let us suppose that the narrow neck of a large enough
glass vessel is put into pne's mouth ; then, the nostrils
being firmly closed, let the air be sucked from the
glass and drawn into the lungs, which will certainly
happen if inspiration begins, the chest being dilated.
But certainly in this case, such a propulsion of the
air from the thorax to the lungs cannot be propa-
gated, because of the interposition of the glass.
But perhaps you will say that some more subtle
matter passes through the glass and is pushed into
the thorax, and that this serves as material for respira-
tion. But indeed if the case were so, how could it be
explained that a small animal shut up in a completely
closed glass will soon die, if particles suitable for
respiration still pass through the glass ?

With respect, then, to the entrance of the air into
the lungs, I think it is to be maintained that it is
caused in the following manner by the pressure of the
atmosphere. For as the air, on account of the weight
of the superincumbent atmosphere, not only rushes
into all empty places, but also presses forcibly upon
whatever is next it (as Boyle's experiments have put

On Respiration 185

beyond doubt), it follows that the air, passed through
the nostrils and the trachea, up to the bronchia or
gates of the lungs, presses against the lungs from
within and seeks an entrance into them. Hence it is
that when the inner sides of the thorax (which by
compressing the lungs from without were resisting
the pressure of this air) are drawn outwards by
muscles whose function it is to dilate the chest, and
the space in the thorax is enlarged, the air which i?^
nearest the bronchial inlets, now that every obstacle
is removed, rushes under the full pressure of the

atmosphere into the cavities of the lungs, and by

inflating them occupies and fills the space of the
expanded chest.

The structure of the lungs is adapted for their
inflation as thus described, for their substance is
composed, as the eminent Dr Malpighi has noted, of
very fine membranes, which form an almost infinite
number of spherical vesicles whose mutual connection
is such that there is easy access from the trachea to
those nearest to it, and from these again to others.
Consequently when these vesicles are inflated by an
inrush of air, the whole substance of the lungs must
necessarily expand.

Nor is it only the pressure of the atmosphere, but
also the elastic force of the air by which it tends to
expand indefinitely, that serves to inflate the lungs
and cause inspiration, as takes place when the air, on
the nostrils being closed, is drawn into the lungs (in
the manner already described) from a glass placed in
the mouth, and also when a small animal breathes in
a glass that has been completely closed. For though
the weight of the atmosphere does not, owing to the
interposition of the glass, press or impel the air which
it contains, still the air, in virtue of its elastic force.

1 86 Mayow

rushes into the expanded chest and lungs of the
breathing animal and inflates them.

And indeed the force with which air that has not
yet expanded seeks to enlarge its volume, is exactly
equal to the pressure of the atmosphere, inasmuch
as it depends upon it, and increases or diminishes
according as this pressure is greater or less. For the
elastic force of the air seems to be due to this, that
the air, especially that near the earth, is compressed
and its volume diminished by the weight of the
superincumbent air ; hence it is that it always strives
to expand, just as a fleece, when the force which
compressed it is withdrawn, instantly unfolds and
expands with a certain motion of restitution. And
this can be confirmed by a well enough known experi-
ment.

For if a bladder with most of the air pressed out of
it, and tied by a tight ligature round the sphincter^
be placed in a glass from which the air is afterwards
exhausted, we shall at once see the bladder swell and
^ become greatly distended, a rather pretty sight by the
way. For although a very little air was contained in
the bladder, yet when the external air (by the pres-
sure of which it was reduced to small volume) is
removed, it immediately expands and inflates the
bladder, indeed sometimes violently bursts it. And^
Y^n fact, the inflation of the lungs is eff"ected in a not
very different way. For as soon as the sides of the
thorax (which by compressing the lungs make them
shrink) are drawn outwards, the air at the entrance to
the lungs is immediately driven into them, whether
by atmospheric pressure or in consequence of its own
elastic force, and distends them.

But we may illustrate the inflation of the lungs in
this way by yet another example. Let us then

On Respiration 187

suppose that a bladder is enclosed in the cavity of a
pair of bellows, and that its neck is so fixed to the
pipe of the bellows which is placed in it, that air
blown into the pipe can pass only into the bladder, as
is seen in Plate II., Fig. 6. (But to ensure this result^
the bladder should be fitted in that manner to the
pipe before the latter is attached to the bellows.)
Further, let the hole be made not as is usual in the
lower blade of the bellows, but in the upper one, and let
it be of considerable size. Let it also be perfectly closed
by a plate of glass, attached to the blade by a suitable
cement, so that the bladder shut up within may be seen
through the glass as through a window. When these
preparations have been made, you will see, if the
bellows are opened by drawing the blades apart, the
bladder swell and extend into the enlarged cavity of
the bellows, as is shown in the figure referred to.
And indeed it is plainly in the same way that the
inflation of the lungs in the dilated chest is produced.
From this we conclude that the lungs are distended
by the air rushing in, and that they do not expand of
themselves, as some have supposed ; for the nmscles^
and fibres which are requisite for any motion are
absent in the lungs. And indeed although the lungs
were provided with muscles, under their contractile
action the lungs would not expand but rather con-
tract, as happens to the bladder and stomach, and
other organs of the kind. And further, when the
thorax is pierced, the lungs in)mediately collapse at
that place — a clear proof certainly that their move-
ment is not spontaneous, but depends entirely on that
of the chest. As for the nerves which are distributed
in the trachea and bronchia, they do not serve for
movement, but for sensation and the nutrition of
these organs.

.t88 Mayow

It will be urged by those who maintain that the
lungs move of themselves, that when the thorax is
wounded the lobes of the lungs usually burst from
the cavity in the chest and protrude through the
opening of the wound, which would by no means
happen if the lungs merely followed the movement of
the chest and did not expand of themselves. This
difficulty is thus answered by the learned Dr High-
more. The air, he says, pressing violently into the
expanded chest and the lungs, does not instantly cease
from its motion, but rushes where the way lies open
and carries the lungs with it, on account of their
extreme lightness, beyond the cavity of the thorax.
But with all respect to such a man, the lungs do not
(as I have ascertained by vivisections) protrude
through the opening made by a wound in the chest
unless the thorax is contracted ; when, namely, the
air does not, as the eminent man supposes, rush into
the lungs, but, on the contrary, is driven out of them.
So that it should rather be said, 1 think, that the
lungs are so compressed by the thorax, which is
everywhere contracted, that they burst forth where
there is an outlet, that is, through the aperture of the
wound ; just as we see a sponge tightly compressed
by the hands, protrude between ths fingers if they
are kept a little apart. But afterwards, when the
chest expands and the lungs are no longer com-
pressed by the sides of the thorax, now drawn
outwards, the lobe of the lungs, which protruded
beyond the cavity of the chest, will immediately
return to it, unless perhaps, in consequence of its
being caught tightly in the lips of the wound, the
outlet for the air is closed and the lobe is kept inflated
outside the thorax.

Nor is there more force in the objection to what

Ofi Respiratio7i 189

has been said, that, in trifling wounds of the chesty
the lungs are yet observed to move somewhat. For
although the air rushes into the thorax through the
aperture of the wound, so that the lungs are externally
compressed by it, still air, in quantity sufficient to fill
the dilated chest, cannot enter immediately on
account of the smallness of the wound, and therefore
air to fill the chest must rush in partly through the
wound and partly through the trachea. Hence the
lungs only partially expand, in the space, namely, of
the enlarged thorax, as yet unoccupied by the air
entering through the wound. But when the chest
contracts, most of the air which has entered through
the wound is expelled through the aperture of the
wound, since its volume is too great to be retained in
the now diminished cavity. When the chest, how-
ever, once more dilates, the air, as before, rushes not
only through the wound but also by the trachea, into
the lungs and dilates them (although with greater
difficulty on account of the mass it has to raise), and
in this way some motion' of the lungs is kept up in
the wounded chest.

Here, by the way, surgeons should be warned not
to close the v^ound if the chest has been perforated
except when the thorax is contracted to the utmost ;
for, otherwise, if the opening made by the wound is
closed when the chest is dilated (that is, when the air
has filled the interior cavity of the thorax), it will be
impossible for the chest to contract on account of the
resistance of the air inside, or for the lungs to expand^
except partially, and, in consequence, suffocation will
necessarily follow.

Now that it has been shown that the entrance of
air into the lungs depends upon the dilatation of the
chest, it remains for investigation how the chest is

1 90 Mayow

expanded. And here, following not so much the
authority of writers as the truth, I shall state briefly
what the thing itself teaches.

The received opinion is that of the intercostal
muscles, only the external serve to dilate the chest,
while the internal, on the other hand, contract it.
But it seems to me more reasonable to suppose that
the chest is dilated simultaneously by both. And
that this may be better understood I shall premise
the following observations.

We may affirm that the raising of the ribs dilates
the space within the chest and that their depression
diminishes it. For we suppose here (what any one
may see in a skeleton) that the ribs (especially the
lower, which contribute most to the dilatation of the
chest) are not articulated to the spine and sternum at
right angles, but that the angles below the ribs are a
little less than right angles ; so that if a rib is raised,
its articulations with the spine and sternum will
approach to right angles. We assert further that
the chest is dilated by the ribs when raised to right
angles. For let us imagine a number of arches lying
upon a plane, as represented in Plate II., Fig. i ; while
they remain in this position there is no space at all
between the arches and the plane, for we suppose that
thev are in mutual contact. If, however, the said
arches are raised somewhat above the plane, there is
a certain intervening space, and, in proportion as they
rise towards right angles, the spaces between them
and the plane become greater. Now it is precisely
the same in the case of the chest. For let a, in the
figure be the spine; 3, the sternum ; and c, c, c, r, the
ribs. Let the plane between the spine and the
sternum be the mediastinum, or any imaginary plane
dividing the thorax into equal parts : how much the

On Respiration 191

more then the ribs arched over the said plane (or
what is the same thing, over the spine and sternum,
which are in that plane) approach to right angles, so
much the greater will be the space which lies
between the raised ribs and the mediastinum, as we
have already shown. And thus it is clear that one
half of the chest is expanded by the ribs being raised
towards right angles, and it is evidently the same
with the other side. As for the false ribs, although
their extremities are connected not with the sternum
but with the diaphragm, they have notwithstanding the
same motion, and in like manner dilate the chest. But
since the ribs when drawn upwards approach nearer
to right angles with the spine, and the ribs when
raised to right angles open up a space in the thorax,
it follows that when the ribs are drawn upwards they
dilate the chest, which is what we undertook to prove.
Nay, any one can experience in himself that the ribs
are drawn upwards in inspiration and the dilatation of
the chest, but that they descend in expiration and the
contraction of the chest.

This premised, if the ribs are raised by the inter-
costal muscles, even the internal ones (which has next
to be proved), it follows necessarily that the chest is
dilated by their contraction.

Whenever, I say, a muscle attached to two bones
contracts, the bone which is less fixed moves towards
the other which is more fixed. Wherefore, since
every lower rib is less fixed than the one above it,
each of the lower ribs must be elevated when the
intercostal muscles, even the internal ones, contract.
For a quite similar reason holds with the internal as
with the external muscles ; nor is it an objection to
this that the former are attached to the ribs in a
different position, as is obvious from Plate II., Fig. 2,

192 Mayow

where the interior muscle a^ a^ will raise the lower
and more mobile rib, in contracting, as well as the
exterior muscle, 3, b. And here it is to be noted
that the ribs are so articulated with the spine that
when they are pulled by the said muscles they easily
ascend and are raised with rotation.

Nay, the very position of the muscles makes this
plain, for if the interior muscle which is placed
between the two lowest ribs were to pull the upper
of the two downwards, all the ribs, since they are
firmly attached to each other, would necessarily be
drawn downwards at the same time, a thing which
that weak and membrane-like muscle cannot do.
How much more probable is it that the lower
ribs are all drawn upwards together by the internal
muscles between the upper ribs, for these are suffi-
ciently strong and broad, while the weaker muscles
between the lower ribs contribute merely to elevate
the lower ribs. These things will be more clearly
seen from Fig. 3, which shows the ribs and the
internal muscles.

And this view is also supported by the oblique and
contrary position of the intercostal muscles. For
Nature seems to have inserted these muscles obliquely
in the ribs (although a direct insertion would have
suited better for moving them up or down) because
the intervals between the ribs are so small that if
these muscles had been inserted at right angles, they
would have been shorter than the nature of muscles
admits. Wherefore, that these muscles should have a
suitable length, they had to be inserted obliquely (as
they are) to the ribs. Yet as this oblique position is
less suitable for elevating the ribs. Nature, that most
wise engineer, has arranged the muscles with divers
aspects so that while they pull the ribs obfiquely with

On Respiration 193

equal force in this direction and in that, the ribs
meanwhile rise straight upwards, as is shown in
Plate II., Fig. 4, where, when the external muscle a^ a^
and the internal c, c, contract together, the lower and
more mobile rib will rise not obliquely but straight
upwards, just as though it were pulled by a muscle
attached to it at right angles. So that clearly the
external and internal muscles contract simultaneously,
and by their united effort elevate the ribs and expand
the chest. Moreover, that the internal muscles do
not cause expiration, may be gathered from the fact
that the thorax in a dead animal is always con-
tracted, for to die and to expire mean the same
thing ; but in the dead, the action of the muscles
altogether ceases ; and so this contraction of the
chest cannot be caused by the internal muscles, since
they no longer contract. Should any one remark
here that that contraction of the thorax is caused
by the internal muscles immediately before the death
of the animal, I ask, in reply, how then is it that the
external muscles (since the two cases are similar)
never contract in the dying, so that the chest should
remain for some time dilated ?

It is probable then that, in expiration, the parts of
the thorax return, by a movement of restitution, to
their natural position without any aid from the
muscles. For it is difficult and contrary to their
natural position for the ribs to be drawn upwards, so
that for this there is indispensable need of the two-
fold and united action of both sets of muscles, the in-
ternal and the external. But the ribs sink down again,
without any work, as is clear in the case of a dead
animal or a skeleton. Wherefore there is no reason
for saying that Nature has provided as much muscular
power for the latter action, which is clearly no

N

194 Mayow

action, as for the former, which is indeed a very difficult
one.
< And here it should be noticed that the ribs are
joined to the spine, not as is commonly believed with
a single but with a double articulation, and that these
joints are placed so obliquely, and shaped with such
contrivance, that the ribs cannot be raised by the
intercostal muscles without being at the same time
drawn outwards for the greater dilatation of the
chest, as is clearly seen in Plate II., Fig. 5 : in which
let «, e^ iy be a portion of a rib whose round head, «,
enters c, the socket hollowed in the spine ; this
articulation is superior and interior. On the con-
trary, in the other articulation, the lower and
exterior, a cavity, but a less conspicuous one, is
hollowed out in the rib at ^, and is articulated with
the protuberance of the spine at b. And now, if we
suppose the head, ^, of the rib to be placed in the
socket, c, of the spine, and the hollow of the rib, ^, to
rest on the protuberance, b^ of the spine, and then
the rib connected with the spine by these two
articulations to be moved upwards, it is easily under-
stood that the rib will be carried to the left, or, what
is the same thing, outwards, in respect to the chest.

These articulations, and also their obliquity, are
more noticeable in the skeleton of a sheep or of a horse
than in that of a man. For it is to be observed that
these articulations are much more oblique in some
animals than in others ; in animals, namely, which,
destined for more violent exercise, have need of more
violent respiration, the joints of the ribs are very
oblique, in order that their ribs may be drawn more
outwards by the contraction of the intercostal muscles,
and that space enough may be opened in the chest
for a sufficiently large expansion of the lungs.

On Respiration 195

Nor should it be overlooked that the cartilages, by
the interposition of which the ribs are joined to the
sternum, are inserted into the ribs with very notable
obliquity, as is shown in Plate II., Fig. 3, in which «, c,
is a rib, c, ^, the cartilage, by means of which the rib
is united to the sternum, ^, the angle formed by the
junction of the two. The obliquity, moreover, has for
its object that the ribs may be extended and drawn
outwards, circularly.

It is, besides, to be noted that in inspiration,
especially when violent, the extremities of the false
ribs move a little inwards ; and the reason is that the
diaphragm is joined to both ends of the false ribs,
with the result that when it contracts, those ends are
drawn inwards, but when it is relaxed they rise to
their natural position.

With regard to the serrate, the longissimus dorsi^
and t\\& pectoralis muscles, it is probable that they have
nothing to do with the expansion of the chest. For
if the hand be placed on these muscles when we
suddenly apply all our strength to dilate the thorax,
it will be found that they neither harden nor draw
together at all ; yet this would happen if these
muscles underwent contraction.

Besides the aforesaid muscles, the diaphragm also
contributes to the expansion of the chest, and indeed
ordinary inspiration seems to be mainly caused by it.
In expiration the diaphragm being in diastole, and
released from constriction and in a flaccid condition,
is pushed upwards into the region of the thorax by
the stomach and the other viscera contained in the
abdomen ; whence it is that it compresses the lungs
and diminishes the space in the chest. But in
inspiration the diaphragm is in systole, and con-
tracted, so that it no longer remains greatly curved

196 Mayow

but is carried downwards and outwards as it flattens.
So that the viscera of the abdomen, which were
previously contained in its concavity, are, now that it
has contracted, forced both downwards and outwards,
and the space in the thorax which was previously
occupied by the diaphragm and the said viscera is now
left free for the expansion of the lungs. And indeed
any one can feel in himself that the ribs rise in
inspiration, while the viscera of the abdomen move
both downwards and outwards under the pressure of
the diaphragm. But all this will be more evident
from an autopsy, for if the chest of any animal is
opened and the diaphragm pressed downwards by the
hand while the ribs are pulled upwards (and this is
not done without much pxertion), you will see that the
chest dilates and that its capacity is enlarged. But as
soon as the supporting force is withdrawn, the chest
will of itself contract anew. For the diaphragm,
pushed by the viscera in the lower part of the
belly, will soon rise into the cavity of the chest, and
the ribs, by descending forcibly to their natural posi-
tion, will still further diminish the cavity of the
thorax.

Hence if the stomach be too full, or if the liver or
the rest of the viscera are much enlarged, respiration
cannot go on except with difficulty, inasmuch as the
said viscera, from their mass, press so much on the
diaphragm as to prevent it from descending and
enlarging the cavity of the chest. Still if, owing to
an urgent necessity for more vigorous breathing, the
violent contraction of the diaphragm forces the
abdominal viscera downwards, notwithstanding their
resistance, it not infrequently happens that its fibres
contract too much in consequence of the violent
strain, so that their tone is almost destroyed and

On Respiration 197

respiration goes on afterwards with difficulty. This
happens not infrequently in the horse when driven
furiously immediately after a rather full meal. For,
since there is need of more vigorous breathing
when great exertions are made, and the diaphragm,
for the wide dilatation of the chest, strives to
descend further than usual, while the much dis-
tended stomach resists its movement, it comes about
that its nervous fibres suffer not a little and are some-
times even broken. And hence when the breathing
of a horse is injured in this way it is often, and not
improperly, said to be broken. But when the
diaphragm is thus weakened, respiration is carried on
exclusively by means of the intercostal muscles, for
these, when violently contracted, raise the ribs in a
notable manner and enlarge the space within the
chest, so that the defect of the diaphragm is to some
extent supplied.

Similarly in Orthopnoea, in which the patient can
only breathe in an erect position, it is probable that
the abdominal viscera press too much on the
diaphragm and keep it up in the chest, so that space
enough for breathing cannot be provided in the
thorax. If, however, the patient be placed in an
upright position, the diaphragm, feeble though it be,
aided by the weight of the same viscera, can force them
downwards. And so, as the abdomen sinks, the chest
dilates and the patient is able to breathe.

And quite similarly in the hysteric passion, when
the organs in the lower part of the belly, convulsed
and swollen, rise in a mass, and keep the diaphragm
up, respiration must necessarily cease and suffocation
follow, as it does. And it is reasonable to think that
this is the cause of uterine suffocation, although I
would not deny that the sympathy between the

198 Mayow

viscera and the throat, arising from nerve communi-
cation may contribute something to this. But
certainly such a constriction of the chest does not
seem to be caused at all by the convulsed and
elevated diaphragm (as the renowned Dr Willis has
supposed), for we have shown above that when the
diaphragm is convulsed in inordinate systole and
violently contracted, it descends and dilates the
chest.

As for asthmatic paroxysms, in which the raised
and distended lungs almost cause suffocation, there is
no reason to think that the lungs are inflated by
convulsion of the pulmonary nerves and thrown into
excessive diastole. For granting that the lungs
sometimes suffer convulsions, the contraction and
convulsion of their fibres (if they have any) would
involve rather the collapse and contraction of the
lungs, as was previously pointed out. Nor is it
probable that the lungs are thus inflated by vapours,
for flatus contained in the pulmonary veins and
arteries cannot inflate them. For even though flatus
be introduced by a tube attached to the pulmonary
artery the lungs will not swell. And any vapours
contained in the vesicles of the lungs could certainly
be expelled with ease along with the air. And
therefore, I think, we should maintain that this kind
of suffocation is caused by the convulsed intercostal
muscles and diaphragm, for by their convulsion the
chest is kept dilated too long, so that the lungs
remain inflated and respiration is interrupted.

Nor should that affection be overlooked here in
which the patient draws breath with difficulty and
with a whistling sound. This ailment does not seem
to arise always from phlegmatic humours choking
the bronchia, but sometimes also in the following

On Respiration 199

manner. When the diaphragm, whether owing to
the pressure of the swollen viscera of the lower part of
the belly or in consequence of its own weakness, is
unable to contract and descend, and the thorax is
therefore dilated only by the movement of the ribs,
it comes to pass that the lungs, inflated by inspira-
tion, cannot, because of the resistance of the
diaphragm, attain their usual well-balanced position,
and their lobes are necessarily bent divers ways ; and
so the bronchia are bent and sometimes greatly
twisted so that the air cannot pass freely through
them, but, striking against them, will produce, as it
does, the sound and whistling. And hence it is that
this sort of afTection sometimes comes on suddenly
after taking flatulent food or drink.

Hiccup has also a claim to be reckoned among
convulsive inspirations, for in it the diaphragm is
contracted by violent but interrupted and often
repeated systole, so that, in consequence of its con-
traction, the chest is suddenly dilated and the air
rushes violently and not without noise into the lungs.
For it must not be supposed that hiccup is produced
by the movement of the stomach, but by that of the
diaphragm. For the stomach when seized by con-
vulsion by no means produces inspiration, as happens
in this affection. Further, when the stomach is
convulsed, the parts about it contract inwardly, as
we can experience in vomiting, but in hiccup the
abdomen is forced outwards, and this, as we have
shown, arises from the contraction of the diaphragm.
Yet since this ailment usually afflicts a too full or
otherwise burdened stomach, we must suppose that
the stomach, or rather its upper orifice which is
attached to the diaphragm, is first affected, and that

200 Mayow

the diaphragm from its nearness and relationship
takes on the convulsive movement.

It seems to be different in the case of that
oppression at night, with difficult respiration, which is
called nightmare ; for this state seems to be produced
not by a convulsion of the parts about the thorax but
by an impediment to the proper influx of spirits.
This oppression generally attacks those who are
falling asleep. For when sleep begins, the spirits
which are the instruments of voluntary functions,
retire towards the cerebrum, or at least no longer flow
copiously from it. Meanwhile the spirits which have
for their office involuntary actions and natural
movements issue in continual flow either from the
cerebrum or from the cerebellum. If, however, in
consequence of any confusion, or from morbid matter
causing disordered movement of the spirits, those of
the latter kind as well as the former, while sleep is
coming on, return towards the brain and are detained
there, not only voluntary, but also natural actions are
necessarily interrupted by the flow of spirits being
impeded. Hence the actions of the heart, the thorax,
and indeed of the whole body cease, so that the
patient is necessarily affected with the very greatest
oppression, suffocation, and a kind of immobility.
That this motion of the spirits is in the wrong direc-
tion may be inferred from this, that the parts of the
body, first those more remote from the brain and
then those nearer to it, are gradually seized with a
certain stiffness and weight in consequence of the lack
of vital spirits. Meanwhile the spirits, detained in
the brain and moving irregularly there, produce a
feeling of giddiness and a disordered imagination.
But when the paroxysm ceases, the spirits rush-
ing impetuously from the brain usually excite a

On Respiration 201

convulsive movement of the body accompanied by a
sudden shout.

The asthmatic paroxysm which accompanies palpi-
tation of the heart will be discussed in the Seventh
Chapter of the Treatise On Muscular Motion.

So much then for inspiration which is effected by
the aforesaid muscles. When, however, their con-
traction ceases the ribs sink of their own accord to
their natural position, and the diaphragm, now relaxed
and flaccid, is raised into the cavity of the thorax by
the upward pressure of the viscera. And this we
have said takes place without any muscular action in
the case of a dead animal. And finally, when the
chest is narrowed at almost every part, the lungs
must be compressed by it and the air expelled ; so
that clearly the lungs do not subside of themselves, but
follow the movement of the thorax.

But to more violent expirations the abdominal
muscles also contribute. For the obliquely ascending
and descending muscles (whose tendons are inserted
into the lower ribs), in their contraction, draw the
ribs downwards and narrow the chest. Further, the
whole abdominal muscles simultaneously contracting,
press the viscera which lie under them, so that the
diaphragm is driven by their pressure and forcibly
urged up into the chest. And any one can find out
in his own case that in sneezing, coughing, laughing,
and in every violent expiration, the muscles of the
abdomen are drawn together and contract. Hence in
laughter and in violent expirations the hypochondria
often suffer pain from the convulsion of the aforesaid
muscles.

From this we gather that laughter takes place
without any action or contraction of the diaphragm.
For in laughter the diaphragm is not, as some have

202 Mayow

supposed, drawn upwards when contracted by
repeated irritations. For in systole and in its con-
traction, it is drawn downwards, as shown above, and
so causes inspiration rather than that expiration
which takes place in laughter. From what has been
said it is evident that risibility is peculiar to man not
because the nerve of the diaphragm communicates in
man, but not in beasts, with the cervical plexus, and
by means of it with the brain — an opinion which the
learned Dr Willis has maintained in his book on the
Anatomy of the Brain. For laughter does not take
place because the diaphragm, on account of an
instigation brought by the said nerve from the brain,
contracts violently with repeated throbs and com-
presses the lungs, as this learned man supposed. For
it has been shown that laughter does not proceed
from the action or systole of the diaphragm, but, on
the contrary, from its diastole.

We have spoken thus far of the manner in which
respiration takes place, and it now remains for us to
inquire into its use. This is indeed a most difficult
affair, for there is not more accord as to its necessity
than doubt as to its use.

For not only is air inspired useful for tasting and
smelling, and expelled, for talking, shouting, cough-
ing, sneezing, and spitting, and again, when retained,
for the expulsion of urine and faeces, for parturition,
and for moving on the chyle, the lymph, and the
blood ; the breath we inspire is destined for a still
nobler use : from which arises such a necessity of
drawing breath that we cannot indeed live a moment
without it.

Some suppose that respiration chiefly serves for
cooling the heart ; but heating rather than such a
cooling seems to suit the circulation and fermentation

On Respiration 203

of the blood. Nor indeed is the more frequent
respiration in violent exercise for the purpose of
cooling the blood which the motion heats. For in
violent exertions, be they so momentary that the
blood is not much warmed, there is certainly need of
more intense respiration than in the greatest state of
heat, and in fevers, that is when the blood boils more
and is as it were on fire ; so that respiration will be
seen to serve not so much for cooling as for motion
itself, as will be shown afterwards.

But the prevalent opinion is that respiration is
necessary to life in order that the blood may be able
to pass through the lungs from the right ventricle of
the heart into the left. For the foetus in the uterus,
whose blood does not pass through the lungs but
through special ducts, does not need to breathe at all.
And this they say is the reason why there is not the
same necessity for breathing in the uterus as after
birth.

But there is no reason why we should say that
Nature has constructed the lungs with so much skill
and labour only that the blood may pass through
them after birth, since it might pass by a shorter and
much less obstructed road through the same channels
it follows in the unborn foetus. Nay, it is the case
that the blood can pass through the lungs apart from
their motion. For if blood or any other liquid is
injected by means of a syringe into the pulmonary
artery of a dead animal it will pass readily enough
into the left ventricle of the heart. And indeed any
one can feel for himself that although respiration be
temporarily suspended, yet the pulse of the arteries in
the wrist is strong enough. But this would not be
the case if the blood were not passing at the moment
through the lungs to the left ventricle of the heart.

204 Mayow

And this will be made still clearer by what is to be
said below. Still I will not deny that the movement
of the lungs, and the compression of the blood-vessels
occasioned by the fall of the thorax in expiration,
contribute not a little to send the blood through the
lungs ; but it is by no means to be supposed that this
is the only use of respiration.

Hence some think that respiration serves a further
purpose, that of churning, forsooth, and dividing into
the smallest particles the thicker venous blood. For
otherwise (as they say) the blood would be separated
into distinct parts, namely, serum and a purple sedi-
ment. But neither is this the chief use of respiration.

For any air, however impure, would suffice for such
a movement of the lupgs and for the churning of the
blood ; but air vitiated by contagion, or air which has
often been sent out from the lungs, is by no means
suitable for respiration and the support of life. With
respect, then, to the use of respiration, it may be
affirmed that an aerial something essential to life,
whatever it may be, passes into the mass of the blood.
And thus air driven out of the lungs, these vital
particles having been drained from it, is no longer fit
for breathing again. But this will be made clearer by
the following experiment.

For if, by means of bellows attached to the trachea
of an animal, a dog for example, the lungs are in-
flated, but in such a way that, through openings
made here and there at their extremities, some of the
air may pass out, the loss of which must be supplied
by the bellows that the lungs may not collapse ; in
this case, I say, the animal will live. And yet that
sort of agitation of the blood cannot take place in
lungs which are kept inflated to the utmost. More-
over, though the movement of the lungs entirely

On Respiration 205

ceases, yet the blood is transmitted through them to
the left ventricle of the heart. But if, on the other
hand, the mouth and nose be closed after breath is
taken and drawn into the lungs, death will certainly
follow, although the lungs remain inflated, because
expiration is prevented. And yet the passage of the
blood through the lungs is as ready in this case as in
the other ; for the comminution of the blood cannot
be greater in the former case, since in both cases the
lungs are equally distended — a clear proof that
respiration is not necessary either for the passage of
the blood through the lungs or for its agitation. But
the reason that an animal lives in the one case and
dies in the other is that in the former there is a
continual access of fresh air, but none in the latter.

As to expiration, it should be noted that it serves
the further use that, along with the air driven out
from the lungs, the fumes which are raised by the
fermentation of the blood are also blown out.

Let us now inquire what the aerial element is
which is so necessary to life that we cannot live for
even a moment without it. And indeed it is probable
that certain particles of a nitro-saline nature, and
these very subtle, agile, and in the highest degree
fermentative, are separated from the air by the action
of the lungs and conveyed into the mass of the blood.
For this aerial salt is so necessary to every form of
life that not even plants can grow in soil to which air
has not access. But if such soil be exposed to the air
and impregnated anew with this fertilising salt, it will
again become suitable for the nourishment of plants.
So that even plants themselves seem to have a kind
of respiration and the necessity of absorbing air.

But it is not so easy to understand the function
which this aerial salt exercises in animal life, yet it is

2o6 Mayow

probable that nitro-aerial spirit, mixed with the
saline-sulphureous particles of the blood, excites in it
the necessary fermentation. And yet it is not to be
supposed that this effervescence of the blood takes
place in the heart alone, but that it goes on first in
the pulmonary vessels and afterwards in the arteries
no less than in the heart. For I do not recognise
that ferment, I know not what, in the left ventricle
of the heart. For whence and by what vessels is
there so great an influx of it as would suffice for
heating so often every day the whole mass of the
blood? In the foetus the blood to a great extent
passes directly from the right ventricle of the heart
into the aorta, and yet this ought not to be done if so
necessary a fermenta^tion took place in the left
ventricle. Much less probable is it that the beating
of the heart is caused by the rarefaction of the blood
in its ventricles as the famous Descartes supposed.
For if the pulsation of the heart were caused by the
fermentation of the blood in its cavities, then, when
the heart beat, its ventricles would be greatly dilated
by that blood, just as a bladder is blown into the form
of greatest capacity. And indeed the blood would
not rush forth so impetuously in the systole as in the
diastole of the heart, and not from an impulse derived
from the contraction of the heart, but on account of
its own rarefaction. But we know in fact, from
vivisections, that the ventricles of the heart are con-
tracted when it beats and are not dilated by the
rarefaction or explosion of the blood, and also that the
blood rushes out when the heart contracts but not
when it relaxes. Indeed, if a motion similar to that
which takes place in systole is excited in the heart of
a dead animal, filled with water or any liquid, the
liquid contained in it will immediately rush forth, not

On Respiration 207

indeed because of an explosion (for of course there is
no such thing in this case) but because the ventricles
actually contract. And further it is obvious that the
movement of the heart is not caused by the rarefaction
of the blood, because hearts are sometimes observed to
beat after being cut out even if the blood has been
pressed out of their ventricles. Indeed, if a solution
of opium or cold water be injected through the
jugular vein, the beating of the heart will immediately
become more frequent, as I have often observed ; but
this cannot be caused by a more frequent heating, for
heating is greatly hindered by substances of that
kind.

So that obviously the heart seems to be nothing
but a muscle, differing but little in its action from
other muscles, and we must believe its function to con-
sist in contraction alone and the expulsion of the
blood.

But although nitro-aerial particles excite fermenta-
tion in the mass of the blood, I do not know whether
it is owing to the want of them that the blood,
immediately upon respiration being checked, becomes
so thick that it is quite incapable of motion, and
stagnates in the left ventricle of the heart. For the
blood while not yet impregnated with air is sent
readily enough from the right ventricle ; and indeed
the left ventricle differs from the right in no other
respect than in the greater power it possesses of
driving out the blood even if it be thicker. And yet
it is not to be denied that nitro-aerial particles
conduce not a little to the fermentation and, conse-
quently, also to the fluidity of the blood, as was said
elsewhere. But, you will ask, how is it then that
death follows so soon upon breathing being arrested
if the blood is not rendered incapable of motion ?

2o8 Mayow

There is certainly yet another use of respiration to
be looked for, one that makes it so necessary. And
what I have thought out on so obscure a matter I shall
shortly state.

Life, if I am not mistaken, consists in the dis-
tribution of the animal spirits, and their supply is
most of all required for the beating of the heart and
the flow of blood to the brain. And it appears that
respiration chiefly conduces to the motion of the
heart in the manner to be stated elsewhere. For it is
probable that this aerial salt is altogether necessary
for every movement of the muscles ; so that without
it there could be no pulsation of the heart.

For if it be allowed that the sudden contraction of
the muscles results frqm the intermixture of particles
of diff'erent kinds, mutually moving each other, then
it is scarcely to be supposed that the particles of both
kinds, by the effervescence of which the contraction of
the muscles is caused, proceed from the mass of the
blood ; for liquids derived from the same source re-
unite without any effervescence, so that it appears
that something extraneous is required for the pro-
duction of the motive fermentation.

We may then suppose that nitro-saline particles
derived from the inspired air constitute the one kind
of motive particles, and that these, when they
meet the others, the saline-sulphureous particles
supplied by the mass of the blood and residing in the
motor parts, produce the effervescence from which
muscular contraction results, as will be shown more
fully in another place.

And in fact motion is produced in the heart in no
different way than in the other muscles ; but I do not
think, for the reasons assigned above, that the motive
effervescence takes place in its ventricles but in its

On Respiration 209

muscular substance, not otherwise than in other
muscles.

Wherefore on the suppression of respiration, as
that aerial salt required for any motion fails, the
beating of the heart and, consequently, the flow of
blood to the brain will necessarily be interrupted and
death will ensue. But one may live for a certain
time without breathing, because the blood contained
in the pulmonary vessels and sufficiently impregnated
with air is capable of moving the heart at least for a
moment.

And this use of respiration can be further confirmed.
For in exercises and violent movements there is need
of more intense and more frequent respiration, not so
much that a greater flow of blood may pass freely
through the lungs — for we have shown that this can
take place when respiration stops — but because there
is a great expenditure of nitro-aerial salt in conse-
quence of the various effervescences made in the
contraction of the muscles ; so that the venous blood
returns to the heart now much impoverished and
thick (and we know that this also happens after
convulsive movements in epilepsy). Wherefore, that
the effete blood may repair the waste, there is of all
things need of more intense respiration. Besides, an
acceleration of the heart's beat is necessary in violent
movements on account of the more copious flow of
blood ; but this can scarcely be effected without freer
supply of nitro-aerial particles — especially since the
blood is now effete. So that a main use of respiration
clearly appears to be to set up the motion of the
muscles and especially of the heart. Hence the frog
which is accustomed to live under water for some
time without respiration will go on living, even when
its heart is cut out ; but to animals which require a

O

210 Mayow

continuous supply of spirits and consequently an
uninterrupted movement of the heart, continuous
respiration is altogether necessary, since without it
the motion of the heart ceases.

Furthermore, if after the motion of the heart has
ceased from the stopping of respiration, air is blown
in through a tube fitted to the vena cava^ we shall see
the heart's motion re-established. So that it appears
that air is that without which the movements of the
heart cannot go on at all. Nor does it matter much
how the air is transmitted to the mass of the blood,
whether by the lungs or by any other way.

To this I add, lastly, that it is proved by Boyle's
experiments that flies, bees, and other insects which
can move with half of their body after being cut
through the middle, can yet neither move nor live in
a place void of air. To these small animals that have
neither blood, nor hearts, nor lungs, at all events not
in their divided parts, air seems to be needed for no
other purpose except motion alone. Finally, accord-
ing to this hypothesis, it is easy to say whence the
beasts of burden that exercise nearly all their muscles
the whole day long, derive an adequate supply of
explosive material for so great an amount of work ;
for what the entire mass of the blood is inadequate to
supply, the air, that freer fountain, can provide in
abundance.

THIRD TREATISE

ON THE RESPIRATION OF

THE FCETUS IN THE UTERUS

AND IN THE EGG

Since the necessity of breathing is so essential to the
sustaining of life that to be deprived of air is the same
as to be deprived of the common light and the vital
spirit, it will not be out of place to inquire here how
it happens that the foetus can live though imprisoned
in the straits of the womb and completely deprived
of the access of air. For it is not enough to say that
the blood of the child is brought during the period of
gestation through the foramen ovale and the ductus
arteriosus^ and circulates well enough without the
movement of the lungs, while the mass of the blood
takes its course, after birth, through the lungs, which
it cannot traverse without the help of respiration.
For respiration serves another purpose than trans-
mitting the blood through the lungs ; otherwise the
lungs would be altogether superfluous, since the blood
could have been carried round by another passage as
is done in the uterus. Nay, the blood can pass
through the lungs themselves without the aid of
respiration, as has been pointed out elsewhere.
Besides, if the foetus which has breathed air for some

211

212 Mayow

minutes only, will die immediately after its breath is
stopped, this is not because the movement of the
blood is prevented ; for the blood could be carried
round by the foramen ovale and the ductus arteriosus^
since these passages, to which it is accustomed, are
not yet closed.

It is therefore to be absolutely concluded that the
necessity for breathing arises from this, that certain
nitro-aerial particles requisite for the support of life
are transmitted by means of the lungs into the blood,
as I consider to be established by what is stated
elsewhere. And therefore inasmuch as the foetus
cannot breathe in the womb, as the air is excluded, it
is necessary that the lack of respiration should be
supplied from another source.

For we cannot agree with those who maintain that
the foetus breathes even in the womb — a view upheld
on the strength of the vagitus uterinus and the suctio
infantuli. But indeed it seems to me that air can
just as well pass to the blood, without respiration,
through the skin and veins, as penetrate the closed
uterus and the many membranes which enfold the
foetus. Although I would not deny that vapours
arising from the fermentation of juices are perhaps
sometimes contained in the amnion ; and these may
produce the vagitus uterinus and the suctio^ but they
cannot serve the purpose of respiration, since they
would need to be driven out oftener from the lungs of
the embryo. Indeed, for the suctio infantuli^ there is
no need at all that air or vapours should be contained
in the amnion, for the external air, by compressing
and pushing not only the outer parts of the body, but,
by their intervention, all the internal parts also, and,
consequently, the liquids of the amnion, is able to
cause suction in the uterus.

On the Respiration of the Foetus^ etc. 213

With regard, then, to the respiration of the foetus in
the womb, we may suppose that the seminal juice
which exudes from the membranes of the uterus, or
from its caruncles, not only supplies nutriment to the
child but also makes up for the want of respiration.
And indeed it is probable that the umbilical arteries
are formed principally and perhaps exclusively for the
sake of respiration. Indeed I know no other purpose
for which they should be fashioned by Nature in every
foetus with such wonderful care and skill. I am
aware of the diversity of opinion that exists among
authors as to the functions of the umbilical arteries,
but I do not know whether among the numerous
offices hitherto assigned to them their true and
peculiar office is to be found.

According to Adrian SpigeHus, the umbilical
arteries convey the blood from the foetus to the
exterior parts, that is, to the secundince^ for their
nourishment. But in fact it is evident if we look at
a hatched ^gg that the membranes (which in the &gg
correspond to the secimdince) are formed while the
umbilical arteries are not yet indicated, from which
we may infer that the said arteries are not formed for
the sake of the membranes. Besides, the umbilical
arteries are so notable in the egg at the very
beginning of life, and their offshoots are connected in
so wonderful a network, that there can be no doubt
that they contribute, in no small degree, to the
formation of the foetus and to the starting of the
dance of life. To this I add further that the
secundince are sometimes in excellent condition
although the foetus is quite corrupt, which is indeed
a very probable indication that the secimdince draw
nutriment rather from the mother than from the
foetus.

214 Mayow

The celebrated Harvey has maintained that the use
of the umbilical arteries is to supply arterial blood for
the concoction and colliquation of the food of the
foetus, and to render it suitable for nutrition ; but it is
scarcely probable that the umbilical arteries should be
designed for this purpose exclusively, since nutritious
juice could be well enough concocted and elaborated
by the mother's heat and the warmth of the uterus.
And it certainly seems foreign to the method of
Nature that blood should be poured on food for its
concoction, as if into a dish. For why should not
nutritious juice be prepared within the body of the
embryo as well in the uterus as after birth ?
Certainly there is no reason why that should be done
through winding patl\s and the long circuit of the
umbilical arteries, which could be managed by a
shorter route and with less trouble. And it also
makes for this that it is probable that the offshoots of
the umbilical vessels are distributed into membranes,
but not into juices to colliquate them, as seems to be
confirmed by the very examination of a hatched Qgg.
And certainly if the openings of the umbilical arteries
terminated in the primogenial juices the said juices
would soon be drenched with arterial blood ; but this
is not the case. Further, we may believe that capillary
vessels, of whatever kind, never end in juices but
always in membranes, for otherwise they would be
less firm and their openings would be closed by the
pressure of the juices on all sides. Indeed, just as the
lacteal vessels which originate in the intestinal
membranes receive the nutritious juice, passed
through these membranes as if through a filter, and
convey it into the mass of the blood, so also in an Qgg
and in other objects of conception we must suppose
that nutritious juice, properly concocted, enters the

On the Respiration of the Foetus^ etc. 215

openings of the umbilical vessels only by a sort of
percolation through the membrane.

In the opinion of others the umbilical arteries are
designed with a view to carry off the excess of food
which is brought to the child through the umbilical
vein. But surely there is no reason for accusing
Nature of gluttony, as though it were not enough to
cram after birth even to surfeit and vomiting without
doing it also in the uterus by the arrangement of
Nature. Further, whatever is carried away by the
said arteries is brought back again by the umbilical
vein, and so the child would be forced, as it were, to
return to its vomit. Nor should it be said here that
only the cruder parts of the blood are conveyed by
the umbilical arteries to the placenta, that, after
further decoction there, they may become fit for
nutrition. For whence, I ask, that elective attraction
in virtue of which it is the cruder parts of the blood
rather than the purer which traverse the ducts of
the umbilical arteries that stand so widely open ?
Further, it is scarcely to be believed that nourish-
ment presented to the child is so raw that it has to
be thrust out of doors to be further cooked. For how
much wiser it would be to prepare it properly at first.

Nor ought we to agree with those who think that
the umbilical arteries exist in order that the blood of
the embryo may circulate by passing through the said
arteries, and then returning by the umbilical vein.
For the blood of the infant can be carried round
easily enough through the aorta and the vena cava
just as after birth. Nor is there any ground for
saying that these vessels are not yet formed in the
embryo ; for it is certain that the great artery in
which the umbilical arteries originate, is in existence
from the first, and indeed it is not in the least to be

2 1 6 Mayow

doubted that the vena cava also exists from the very
commencement of life. For why should not Nature
be as ready to form the vena cava as that long circuit
of umbilical vessels which are quite useless after birth
and have to be destroyed ?

Wherefore, since the functions hitherto assigned to
the umbilical arteries do not appear to be suitable and
real, we may hold with divine old Hippocrates that
in the embryo the umbilicus supplies the place of
respiration, which is also the opinion of the learned
Everard.

But I cannot agree with Everard in the reason he
assigns for setting up respiration in the uterus. For
this learned man thinks that the blood of the infant is
conveyed through the^ long circuit of the umbilical
vessels in order that it may be cooled in its journey.
But indeed it is by no means to be believed that such
a cooling of the blood takes place in the very warm
uterus. And even though there were such cooling, it
would serve in no way the purpose of respiration, for,
as we have shown elsewhere, this contributes rather
to the heating than to the cooling of the blood.

But now that we may prepare the way for our
opinion as to respiration in the uterus, we observe, in
the first place, that it is probable that the albuminous
juice exuding from the impregnated uterus is stored
with no small abundance of aerial substance, as may
be inferred from its white colour and frothy character.
And in further indication of this, the primogenial
juices of the ^gg^ which have a great resemblance
to the seminal juice of the uterus, appear to abound
in air particles. For if the white or the yolk of an
^gg be put in a glass from which the air is exhausted
by means of Boyle's pump, these liquids will im-
mediately become very frothy and swell into an

On the Respiration of the Foetns^ etc, 217

almost infinite number of little bubbles and into a
much greater bulk than before, a sufficiently clear
proof that certain aerial particles are most intimately-
mixed with these liquids. To which I add that the
humours of an Qgg when thrown into the fire, give
out a succession of explosive cracks, which seem to be
caused by the air particles rarefied and violently
bursting through the barriers which confined them.
And hence it is that the fluids of an Qgg are possessed
of so fermentative a nature. For it is indeed prob-
able that the spermatic portions of the uterus and its
carunculae are naturally adapted for separating aerial
particles from arterial blood.

These observations premised, we maintain that the
blood of the embryo, conveyed by the umbilical
arteries to the placenta or uterine carunculae, brings
not onl}^ nutritious juice, but along with this a portion
of nitro-aerial particles to the foetus for its support ;
so that it seems that the blood of the infant is
impregnated with nitro-aerial particles by its circula-
tion in the umbilical vessels, quite in the same way as
in the pulmonary vessels. And therefore I think that
the placenta should no longer be called a uterine liver
but rather a uterine lung.

Should any one object here that such a mode of
breathing in the uterus could be carried on without
umbilical arteries, since it would suffice if the
nutritious juice were to pass, charged with nitro-aerial
particles, to the foetus through the umbilical vein, I
answer that to supply the part of respiration there is
need of a continuous supply of air, but that the
nutritious juice should not be in such abundance as to
come to the child in a perpetual stream, and therefore
it is necessary that the umbilical arteries should be
so formed, that the arterial blood, continuously sent

2i8 Mayow

out to the placenta, may be there impregnated with
a portion of nutritious juice charged with aerial
matter ; and that it should return thence, with never
interrupted motion to the foetus, for the purposes at
once of nutriment and of respiration.

For indeed it is probable that if arterial blood,
which is imbued with nitro-aerial spirit, came to the
heart instead of venous, there would be no need at all
for respiration. And this seems to be confirmed by
the fact that when arterial blood, in what is now a
well-known experiment, is transmitted from one dog
to another, the dog to which the blood is transferred,
although previously panting and breathing violently,
yet, after receiving the arterial blood, seems scarcely
to breathe at all.

OF THE RESPIRA TION OF THE CHICK IN THE EGG

Thus far of respiration in the uterus ; it remains for
us to discuss briefly the respiration of the chick in the
Qgg. For there can be no doubt that the want of
respiration in the egg also is supplied from another
source. It is in fact our opinion that the chick in the
Qgg respires through the umbilicus very much in the
same way as the child in the uterus. For when I
contemplate the really marvellous and complicated
network of the umbilical arteries in the incubated
egg^ and then consider that none of the things
essential to animal life are wanting in the egg^ except
respiration only, assuredly I can arrive at no other
conclusion than that the aforesaid vessels are formed
to compensate for the lack of respiration.

Wherefore, let us now inquire how the umbilicus
in the egg supplies the place of respiration. In

On the Respiration of the Fcetus, etc. 219

regard to this it is probable that the primogenial
liquids of the egg (which, as has been already shown,
abound with aerial matter), continuously brought by
the umbilical vessels to the chick, perform for it the
part of not only of nutrition but also of respiration,
just as is done in the uterus.

If any one shall here object that there is not so
much air contained in the egg as is required to supply
the want of respiration during the -vyhole period of
incubation, I answer that the air stored in the ^g'g is
not common air but is that aerial something which is
separated from common air by the action of the lungs.
Indeed, of the air which we inhale it is only a very
small portion that is transmitted into the mass of the
blood ; what remains of the air is expelled in ex-
piration as being useless. But what there is of air,
pure and vital (such as we are to suppose contained in
the ^gg)^ may be compared and held to be equal to a
great quantity of common air.

Nor is it to be forgotten that the foetus in the egg
and in the uterus makes but the very smallest
expenditure of nitro-aerial particles ; for these are
mostly required for muscular contraction and for
carrying on the concoctions in the viscera, as we shall
elsewhere show. Hence, according as any one
exercises himself more or less, so he has need of a
more intense, or of only a more moderate respiration.
And undoubtedly in drowsy affections, in which the
animal functions are almost suspended, respiration
seems to be all but suppressed. Wherefore, as the
foetus in the uterus and in the Qgg keeps holiday from
nearly every movement except that of the heart, a
smaller ration of nitro-aerial particles from the arterial
blood of the mother, or from the fluids of the Qgg^
abundantly suffices for its requirements.

220 Mayow

Let us also ponder briefly whether the gentle
warmth produced in the egg by the heat of the
incubating fowl does not contribute in some measure
to compensate for the want of respiration. For it
was elsewhere shown that nitro-aerial particles are
detached from the aerial particles by the fermentation
of the blood, and that these, in animals, serve the
purpose of respiration. Further, it ought to be
noted that heat of all kinds is produced by the
motion of nitro-aerial particles.

But now as it is altogether needful for the genera-
tion of the chick that a gentle warmth be excited in
the Qgg^ by the heat of the incubating fowl or other-
wise, why should we not suppose that nitro-aerial
particles (from the copimunication of which to the
t,gg its warmth arises) supply to some extent the
place of respiration in the ^^^ ? Certainly the nature
of the white of egg seems to be such as is suitable
for the detention and entanglement of nitro-aerial
particles, inasmuch as it consists of a viscid fluid, and
that, too, impregnated with saline particles liberated
from union with sulphureous particles. It corro-
borates this view that the white of an Qgg^ if whipped
rapidly with a rod or spoon, becomes frothy more
than all other substances on account of the abundant
intermixture with it of aerial matter. It is therefore
probable that nitro-aerial particles, when conveyed to
the Qgg by the warmth of the incubating fowl, are
detained there by its albugineous humour ; and that
when at last collected by the almost innumerable
ramifications of the umbilical vessels and then
brought in great abundance to the foetus, they
compensate in some degree for the want of respiration
in the Qgg. For the chief use of the respiration
of animals is to introduce nitro-aerial particles

On the Respiration of the Foetus^ etc. 221

into the mass of the blood, and it does not matter
how this is done. And indeed the tepor produced in
the egg by the warmth of the incubating fowl
produces the same effect in its primogenial juices as
the nitro-aerial particles do in the mass of the blood.
For just as the nitro-aerial particles passing into the
earth along with heat and moisture, effervesce with
its saline-sulphureous particles, on which action the
life and respiration of plants depend, as has been
elsewhere shown, and as nitro-aerial particles densely
mixed with the blood through the agency of the
lungs excite the fermentation required for animal life,
so also the same nitro-aerial particles entering the
juices of the Qgg under the form of a genial heat
appear to contribute to some extent to set up in them,
vital fermentation and animal movement, and so in a
measure to perform the part of respiration. And
hence it is that the tepor, whether produced by
incubation or in some other way, is so necessary for
sustaining the life of the chick in the egg. For if an
egg is opened after some days of incubation, in such
a way that the salient point comes into view, you will
find that according as the egg is exposed to heat or to
cold, the little heart of the chick is beating in the
one case, and in the other languishing and ceasing to
move as if respiration were suppressed.

From what has been said it is not very difficult to
understand how it is that the foetus, if wrapped in its
unbroken membranes, can live for several hours after
birth without danger of suffocation ; while yet if it has
once taken air into the lungs after being stripped of
its membranes, it will not be able to survive for a
single moment without air, but will immediately die,
as has been recorded by the illustrious Harvey. It is
not enough to say here that the blood of the infant,

2 22 Mayow

after respiration once begins, is taken round by an
entirely new path through the lungs, and that it
cannot be transmitted through them without their
continuous movement. For I think it is clear from
what has been said that this answer fails to remove
the difficulty. It should rather be said, I think, that
the albugineous juice contained in the placenta, or in
the membranes in which the foetus is enclosed, have
a supply of nitro-aerial particles large enough to
continue for a time the respiration and the life of the
infant. Indeed, the foetus when born and wrapped in
its unruptured membranes, seems to be in nearly the
same case and to breathe very much in the same way
as the chick enclosed in the Qgg. If, however, the
foetus is stripped of its, membranes, and contracts the
muscles of the chest and the diaphragm that respira-
tion may begin — certainly no small exertion — there is
now a greater expenditure of nitro-aerial particles for
muscular effort, and consequently the foetus is under
a greater necessity to breathe, since nothing is any
longer received to supply the want of respiration.

It will not be irrelevant to inquire here whether
the air which is contained in the cavity in the blunter
end of every q^^^ contributes to the respiration of
the chick. This cavity lies between two membranes
which are stretched over the whole interior of the
Qgg. For of these membranes, the one which is next
the shell is in all parts firmly attached to it, but the
other, which is next the fluids of the ^gg^ adheres
almost everywhere to the first, except that by reced-
ing from it a little at the blunt end of the Qgg^ it
forms the aforesaid cavity there. Harvey and others
have supposed that this cavity lies between the
membrane which envelops the fluids and the shell,
which is left bare at that place by the other

On the Respiration of the Foetus^ etc. 223

membrane, but I have ascertained that the shell of

the egg is everywhere lined by the first membrane

and that the cavity lies between the two membranes.

With regard to the purpose served by the air

contained in this cavity, I cannot agree with the

learned Fabricius who maintains that air is stored in

it for the respiration of the chick ; for there is so

little of it that it would barely suffice for once

starting respiration. Besides, the air enclosed in the

cavity is completely shut out from the foetus by the

intervening membrane, so that it cannot pass to the

foetus for the purpose of respiration, as will be evident

from the following experiment. For let the sharper

end of an Qgg be so broken that its fluids can be

poured out in order that the said cavity may be seen,

which in eggs that are not yet hatched will be very

small. Then let the Qgg be put into a glass and the

air pumped out by Boyle's pump.

When this is done the small portion of air con-
tained in the cavity will at once expand when the
pressure of the atmosphere is withdrawn, in virtue of
its elastic force, and will push forward the membrane
covering it a long way, so that the cavity will enlarge
to half the size of the egg, more or less. Nay, the air
sometimes by separating the said membrane from the
other to which it was previously attached, will push it
beyond the cavity of the egg. And from this we may
infer that the air cannot pass through the lining
membrane and be conveyed to the chick, for if it did,
this membrane would not be pushed so far by the
enclosed air nor become distended.

But since that air within the egg cannot reach the
chick for the function of respiration, let us inquire
what purpose it serves. For it is by no means to be
believed that the air which Nature has so carefully

224 Mayow

placed in every Q,gg is altogether useless and super-
fluous. But in order to understand the function of
that air, it must first be noted that the seminal juices
of the egg when colliquated by incubation are not
rarefied or expanded, but are on the contrary con-
densed and forced into a narrower space than before.
For we remark that the aforesaid cavity is greatly
enlarged after a few days' incubation, as will be
manifest if the blunt end of the egg is perforated.
But this would not at all be the case unless the juices
which filled nearly the whole of the Q^g before
incubation were subsequently, by the incubation,
condensed and made to occupy less space than before.
In fact the humours of the egg are contracted after
they have passed into the body of the chick, to about
a half less than they*" were at first, since the cavity
enlarges under incubation to about half the size of the
whole Qgg,

But now let us consider briefly how it is that the
juices of the egg are condensed to such a degree by
incubation ; and it is to be noted that things may be
condensed in various ways :

I. If vacant spaces numerously interspersed among
the particles of the thing to be condensed are
diminished or even removed by the particles
approaching each other. But it is not probable that
the juices of the o,^^ are condensed in this way only.
For it is by no means to be believed that as much
empty space should be distributed among the juices of
the egg as is required for contracting them to the
extent of about one half. For if such were the case
the juices of the egg would contract very much on
account of the pressure of the atmosphere when the
shell is perforated. Yet this does not at aP. take
place.

On the Respiration of the Foetus^ etc. 225

2. A thing will undergo condensation if its particles
which have expanded on being set in motion are
afterwards, on the subsidence of the motion, reduced to
narrower space. But neither in this way are the juices
of the Qgg condensed, inasmuch as they are colli-
quated and fermented by incubation, so that the motion
of their particles is necessarily greater than before.

3. A thing might be condensed if some more subtle
matter interposed among its particles extricated itself,
so that the parts of the thing might approach nearer
to each other. And indeed it naturally occurs to one
to say that the rarer part of the albumen exhales,
and that the juice is reduced in consequence to less
bulk than before. But, indeed, this cannot happen in
the Qgg^ because its very compact shell and also the
membranes enveloping the juices of the egg^ prevent
any part of these juices escaping out of the &gg^ especi-
ally since in the incubated Qgg a greater space than
before is provided for the reception of these juices.

4. Condensation of a thing may take place because
some elastic matter distributed among its particles
becomes afterwards less elastic ; and it is especially in
this way that the juices of the Qgg seem to be con-
densed. For it is probable that the air distributed
among the juices of the egg loses its elastic force on
account of the fermentation produced among these
juices by incubation, just as takes place in the mass of
the blood, as has been shown above.

Since the seminal juices of the Qgg become more
contracted in this wa)^ by incubation and are reduced
to smaller bulk than before, there would be a vacuum
in the incubated egg if prudent nature had not, to
avoid this, stored in the egg a small quantity of air
which by its elastic force might extend itself into the
space left vacant by the condensation of the juices.

P

226 Mayow

And hence it is that the said cavity is so much
enlarged by incubation. For we must not suppose
that this enlargement of the cavity is produced by
the access of new air, but by the pressure of the air
inside. For although when the blunter end of the
egg is perforated, the said cavity is found to be much
larger than in new-laid eggs, yet if the sharper end is
broken and the juices of the egg poured out, the
membrane spread over the cavity (which, by the con-
traction of the juices of the egg and by the elastic
force of the air, was thrust far into the region of the
egg) will immediately fall back, on account of the
pressure of the external air introduced into the
perforated egg^ and be applied anew to the shell ; so
that the cavity will not now appear larger than in
unhatched eggs, unless perhaps the air enclosed in it
be still warm and rarefied, in consequence of the
warmth of the incubating fowl — a clear enough proof
that the enlargement of the cavity is due to the
elasticity of the air inside, in virtue of which it
expands into and occupies the space left by the
contraction of the juices.

Nor yet is it to be supposed that precaution is
taken against a vacuum in the egg^ as though nature,
according to the common belief, abhorred a vacuum,
but rather because a vacuum would not be so suitable
for the generation of the chick. And indeed it is
reasonable to think that the air stored in the egg^ in
consequence of its elastic force (increased not a
little by the fostering warmth of the incubating fowl)
gently compresses the colliquated juices of the egg
and drives them into the umbilical vessels, and hence
contributes not a little to the commencement of
animal motion.

It is, moreover, likely that the air inside the egg

On the Respiration of the Faetiis^ etc. 227

contributes still more to the growth of the chick and
to the building up of its structure. For it should be
noted that the seminal juices of the egg, colliquated
from the beginning of the incubation, formed a fluid
body, and that, therefore, among their particles flow-
ing hither and thither, there must have been inter-
spersed a great number of little spaces. But when
the primordial particles go combined together into
various parts, they compose no longer a fluid but a
solid body, such as is that of the embryo ; and, what
is to be chiefly noted, the particles, becoming much
more compact, are brought into a smaller space, as
was remarked above.

But since the air enclosed in the ^^^ is always
compressing the primogenial juices by its elasticity,
that tends to bring it about that the seminal particles,
united most closely together, are reduced to the
smallest possible space. And this result is at last
attained when the particles adapted for forming this
and the other parts mutually embrace each other and
pass into the body of the embryo, since the primo-
genial juices, when converted into the body of the
chick, are reduced in bulk by about one half. So
that, clearly, that internal air, by compressing and
pushing the primordial juices of the Qgg^ appears to
perform the same work as the steel plate bent round
into numerous coils by which automata are set in
motion.

And, lastly, it is also to be noted, that when the
juices of the tgg are forced into smaller bulk by
incubation in the manner aforesaid, the shell of the
^gg would scarcely be strong enough to resist the
pressure of the external air, unless that internal air,
its elasticity in no small degree increased by the heat
of the incubating fowl, supported it.

FOURTH TREATISE

ON MUSCULAR MOTION AND ANI-
MAL SPIRITS. INCIDENTALLY,
ON THE MOTION OF THE BRAIN,
AND ALSO ON THE USE OF THE
SPLEEN AND OF THE PANCREAS

CHAPTER I

EXAMINATION OF THE VARIOUS OPINIONS OF
AUTHORS AS TO THE WAY IN WHICH MUSCLES
CONTRACT

That Nitro-aerial Spirit is, by means of respiration,
transmitted into the mass of the blood, and that the
fermentation and heating of the blood are produced
by it, has been elsewhere shown by us. But I shall
now further add concerning the use of that inspired
spirit, that it takes the chief part in the origination of
animal motions, an opinion which I published now a
good while ago, and still firmly hold ; not that I have
set myself to stick to it, as fixed to a preconceived
hypothesis, but because I consider it most agreeable
to reason.

The cause of the production of any kind of motion
is so obscure, that the consideration of it may exercise
the minds of the anatomists nowadays, no less than

229

230 Mayow

of the philosophers long ago. As if, indeed, human
ignorance should be nature's laughingstock, for those
things that are seen every day in our hand and before
our eyes recede furthest away from the grasp and
perception of our minds, like the unhappy case of
Tantalus. And among these Motion deserves to be
reckoned, for we know so little how it takes place
that, notwithstanding the evidence of our eyes, its very
existence has been sometimes considered doubtful, and
one of the famous questions discussed in the Schools
was — Is Motion to be taken for granted ? And the
Sophist so firmly denied this that it would have been
all up with its existence, had not Motion itself, stirred
up in its own defence, made answer, and set the Peri-
patetic against the Philosopher. But now, if there
are such various difficulties as to motion in general,
how much more obscure is that animal motion, in
which we see to our astonishment enormous bodies
execute quite stupendous movements of their own
accord.

No one doubts that the movements of animals are
produced by the contraction of the muscles, but how
that contraction is brought about is the subject of
varied controversy among authors. Still, the most
generally received opinion is that the fibres of the
muscles are inflated with some elastic matter, so that
while they swell as to breadth they contract as to
length.

And this inflation of the fibres is thus described by
that very distinguished man, Dr Willis, in his Discus-
sion on Muscular Motion. This learned man thinks,
namely, — "That the Animal Spirits carried from the
brain by the channel of the nerves are stored up in
the tendinous fibres, as in suitable repositaries ; but
that these spirits, on the incitement to motion being

On Muscular Motion and Animal Spirits 231

given, spring forth from the tendinous into the fleshy
fibres, and there, meeting active particles of another
sort, supplied by the blood, immediately effervesce with
them, so that from the struggle and agitation of them
both, the fleshy fibres, being lax and porous, are stuffed
out and corrugated, and that the contraction of the
muscle is produced by the corrugation at the same
time at both ends of all these fibres. But when the
contraction is over, the unused spirits that are left
again in great part retire into the tendinous fibres,
leaving the other particles within the fleshy fibres,
and then the blood, as also their nerves repair the
waste of these fibres. But as to how the spirits stored
in the tendinous fibres are brought thence into the
fleshy fibres for the production of motion," our learned
author supposes " that an impulse transmitted by the
nerves, as it were a token, is required, and that this
is done by other spirits sent from the brain, while,
namely, these inflowing spirits, by their varying
approach to the muscles, regulate the innate spirits in
their various movements, whether of expansions or of
retreats."

This theory of the learned author is certainly very
ingenious, but I am not sure that it is in the same
degree in accordance with truth.

For, in the first place, the inflation of the fibres in
the way described is beset with various difficulties,
and these of no small weight. For if a muscle is con-
tracted by the inflation of its fibres, it would neces-
sarily follow that, being distended towards the outside
in its contraction, it would swell into a much greater
size ; but it has been found by observation that a
contracted muscle is drawn more closely together and
becomes hard, and that, if it does not become smaller,
yet certainly it does not swell up to such an extent as

232 Mayow

would be required for its contraction, if that were
brought about by the inflation of its fibres, as has
already been noted some time ago by Lower. But
that in some contracted muscles we seem to feel a
tumour, does not, I think, come so much from their
swelling as from the movement of the belly of the
muscle, in its contraction, towards the fixed tendon,
so that the ascent of the belly of the muscle caused in
this way, raises a hand placed on the muscle and
simulates a tumour.

Further, if some elastic matter contained within
the passages of the fibres inflated them in the way
described, how could it be that the fibres should in a
moment subside again, as happens in the glance of
the eye and in other iiastantaneous contractions of the
fibres ? For neither can I comprehend how that
elastic matter should in an instant inflate the fibres
and again extricate itself from their passages, for if an
easy way out of the fibres lay open to that rarefied
matter, it would pass quickly through the fibres and
not properly inflate them.

Moreover, it is hardly likely that the animal spirits,
in the relaxation of the muscle, return from the fleshy
into the tendinous fibres, for it is not easy to conceive
what should regulate these spirits in their movement
of retreat. Besides as, according to the opinion of
the learned author, the animal spirits springing forth
into the fibres meet there particles of another kind
collected in sufficient abundance, and at once, as a
whole, mutually effervesce with them, it would seem
that these spirits would either be wholly dissipated, or
be changed into something else quite different from
what they were before ; so that they would become
altogether unfit for again exciting effervescence.

Finally, as to the part of the muscle which primarily

On Muscular Motion and Animal Spirits 233

undergoes contraction, it is probable that not so much
the fibres, as the fibrils inserted transversely into them,
chiefly undergo contraction, as will be shown after-
wards.

As to the swelling of the fleshy fibres observed close
to a ligature tied upon them, that seems to be pro-
duced by the blood passing through on the one side
and on the other, but not from the interrupted motion
of the animal spirits. For if such a swelled fibre be
wounded, blood immediately escapes in abundance.
Besides, that tumour remains constant at the ligature
even when the muscle is relaxed and is no longer
contracted, and then the animal spirits are not sup-
posed to advance out of the tendinous fibres, but, on
the contrary, to retire into them.

But so far I think we may agree with the learned
author, for I believe that the contraction of the
muscles is produced by particles of different kinds
mixed with one another in the structure of the muscle,
and mutually effervescing, as will be shown below.

I am quite aware that the learned Dr Steno, in his
Myologice Specimen^ published not very long ago,
thinks that there is no need that any elastic matter
should be added in order to start the contraction of
the muscles ; which, in this learned author's opinion,
can be effected by a mere change of their form.
Thus, '*If a muscle should change from an obHque-
angled parallelogram into a parallelogram the angles
of which are less acute, as is supposed to happen in
the contraction of the muscle, then it will be con-
tracted in length, and will also swell up, without the
addition of any new matter " ; as is shown in Plate III.,
Fig. I, in which, let «, h^ c, d^ be the muscle, c, </, ^,/,
the same contracted, and although it be of the same
magnitude as before, and has had no new matter

234 Mayoiv

added to it, has yet undergone contraction as to
length, and besides, rises at / into a tumour. But,
indeed, it is hardly to be believed that muscular fibres
should be ready to start this sort of motion unless
some new matter were added for that end ; for, as the
structure of an uncontracted muscle is lax, it would
seem that the fibre b^ d^ in its contraction should not
be carried outwards towards /, but rather, on the
contrar}^, should go inwards. Again, if the contracted
muscle is of the same size as before, and if no new
matter has come to it, how is it that in its contraction
it becomes so hard and tense, as any one can find out
in himself by placing his hand on a contracting
muscle ? And finally, what indeed could contract the
fibres and cause a charage of this sort in the muscle if
nothing flowed into it ? Nay, it is quite evident that
some new matter brought by the channel of the
nerves is required for starting the contraction of the
muscle, inasmuch as, if the nerve distributed to a
muscle be cut, the contraction of that muscle becomes
impossible.

I confess, for my part, that if we concede the arrival
of new matter for accomplishing the contraction of
the muscle, its contraction can be produced by a
mere change of its shape ; as will be seen in the figure
referred to, in which, when the muscle a^ 3, c, d^ is
inflated by the motive influx, it necessarily follows
that the fibres a^ c^ and 3, d^ are brought towards a
position at right angles to the tendon c, d^ which we
assume to be fixed, and that the other, the more
mobile tendon, is drawn outwards so that the inflated
muscle will be c^ d^ e^ i. For that muscle could, by
no other change produced in it, be enlarged for the
reception of new matter and be thus inflated. But
while the muscle is thus changed as to shape, it

On Muscular Motion and Animal Spirits 235

swells as to breadth, but becomes less as to length ;
and in this way a muscle can be shortened, although
its fibres suffer no contraction.

But whether a change of this kind takes place in a
muscle, and its contraction depends on this alone, I
shall not say for certain. Still, it does appear to me
that a contracted muscle does not swell up so much as
would be required if its contraction were caused in
this way. Besides, I do not see what part of the
muscle should sustain the attack of the motive matter
in such contraction, for some kind of membranous
vesicles, rather than muscular cords, would be suitable
for bearing the force of contraction, and yet the
strength of a muscle seems to proceed from its fibrils
and cords rather than from any kind of vesicles or
membranes. But these things will be discussed more
fully below.

CHAPTER II

A SHORT DESCRIPTION OF MUSCLES. ALSO WHAT
PART OF A MUSCLE PRIMARILY CONTRACTS

In the anatomical dissection of muscles the first thing
that presents itself is a membranous integument spread
in all directions over each muscle ; under which come
into view series of fleshy fibres ; these, parallel among
themselves, are inserted obliquely into the opposite
tendons, which are parallel one to the other, as the
eminent Steno first observed.

Next, there come to view the wonderful series of
almost infinite membranous fibrils, which, parallel
among themselves, cut the fleshy fibres obliquely, for

236 Mayow

indeed, just as the fleshy fibres are inserted into the
tendons, so are the fibrils into the fleshy fibres, but
arranged the contrary way ; and as the fibres closely
joined together seem to form the tendons, so the
collection of fibrils seems, in part at all events, to
form the fibres themselves ; as is seen in Plate III.,
Fig. 2, which shows the series of fibres and of fibrils,
as they are seen in muscles that have been boiled for
a suflSciently long time.

Hitherto it has been held by the authors best
acquainted with anatomy that the fleshy fibres of the
muscle chiefly and primarily undergo contraction ; but
in our opinion (which I should wish to express with
all respect) not the fibres but the fibrils inserted trans-
versely into them, take the chief part in muscular
contraction, and this we gather from indications which
are at all events probable. For if the contraction
took place in the fleshy fibres, then, for a due contrac-
tion of the muscle, it would be necessary that the
fibres should be much more shortened than the
muscle itself; for as the fibres are not arranged
according to the length of the muscle, but are inserted
obliquely into the tendons, as may be seen in the
figure referred to, it follows that the contraction of
the muscle is much less than the contraction of the
fibres ; and that for a proper contraction of the muscle
it would be necessary that the fibres should be con-
tracted much more than the muscle itself: but I do
not think such a great contraction of the fibres really
occurs in motion : for, besides that we cannot in
vivisections see this sort of contraction of the fibres, if
the fleshy fibres contracted so much, the muscle
should swell enormously, but it does not.

Besides, in order that the contraction of the muscle
should be effected by the fibrils, there is no need that

On Mtiscidar Motion and Animal Spirits 237

they should contract and swell up so much, inas-
much as their series are, as is shown in the figure
referred to, arranged according to the length of the
muscle, so that the contraction of the muscle will be
equal to that of the fibrils. But now, as nature is in
the habit of taking the shortest road, it is probable
that the contraction of the muscle is produced by the
contraction of the fibrils rather than by that of the
fibres. And it also tells in favour of this, that, as the
fibrils are very small and very short, their contraction
even to a half would scarcely be anything remarkable ;
for as the fibrils suffer contraction as a whole, the case
is just as if fibres stretched according to the length of
the muscle were forced into manifold corrugations,
and their contraction, taking place thus, although it
be pretty great, can yet occur without notable swell-
ing of the muscle.

To these T further add that the shortened fibrils
draw the fleshy fibres together and constrict them : so
that it is probable that the contraction of the muscles
is accomplished by the fibrils ; inasmuch as a muscle
when contracted is conspicuously constricted and
becomes hard ; and it does not seem that this could
take place in any other way than by the contraction
of the fibrils. But there will be a fuller discussion of
the constriction of the contracted muscle later.

Moreover, it is nature's custom very often to carry
on her operations by means of very small things, so
that the fibres seem too thick and coarse for muscular
contraction to take place primarily in them ; and it is
probable that they serve rather for transmitting blood
than for carrying on animal motion, as will be shown
below.

Lastly, it tells in favour of this, that the shortness
of the fibrils and their almost infinite number con-

238 Mayow

tribute to the strength of the muscles and to the
more effective performance of their pull. Certainly
the fibrils, whether we consider their number, their
size, or their position, would seem much more fit for
bringing about muscular contraction than the fleshy
fibres. And this is further much confirmed by actual
inspection; for, so far as. I have ever been able to
attain in examination by vivisections, the fleshy fibres,
in the contraction of a muscle, as if attracted by the
transverse fibrils, seemed to come nearer one another,
and not to be themselves shortened, but to follow the
contraction of the fibrils.

As to the fact that, in consequence of a ligature
being tied round each end of the fleshy fibres,
muscular contraction ceases and the fibre itself does
not, as it otherwise would, swell up, as has been noted
by the eminent Dr Willis, I think this due to the
interruption, by means of the ligatures, of the motion
of the blood and of the animal spirits, an inflow of
which is necessary for the contraction of the fibrils.

CHAPTER III

OF THE PARTICLES BY MEANS OF WHICH MUSCU-
■ LAR CONTRACTION IS EFFECTED ; AND IN THE
FIRST PLACE OF THE MOTIVE PARTICLES
BROUGHT BY THE BLOOD; INCIDENTALLY, OF
THE STRUCTURE AND USE OF MUSCULAR
FLESH

In the previous chapter I have endeavoured to show
that muscular contraction is chiefly caused by the
fibrils. Let us now, in the next place, see by what

On Muscular Motion and Animal Spirits 239

cause the contraction of the fibrils is effected. There
can be no doubt that the influx of animal spirits is
necessary for the performance of the motive function,
inasmuch as if a nerve is cut or obstructed, the
muscle to which it is distributed refuses to contract.
But it is not to be supposed that the contraction of
the muscles depends on the .animal spirits alone, since
for carrying it out there is absolute need of other
particles besides, brought from the mass of the blood.
For, seeing that the arterial blood is supplied to the
muscles in a continuous flow, and, especially in more
violent movements, in a fuller flow than to other
parts or than is required for their nutrition, it may be
concluded that the arterial blood in its transit de-
posits something necessary for the contraction of the
muscles. For, indeed, such is the structure of muscles
that in their contraction they draw themselves
together, and thus greatly promote the motion of the
blood ; and that is why the motion of the blood is so
much accelerated in rapid running. And we can
easily put this to the test, if, when the median vein
has been opened, the muscles attached to the forearm
are contracted (and this can be quite well accomplished
if the fingers are pressed together in flexion), for when
this is done, the blood will be seen to rush out forcibly,
being pressed out of the said muscles by their contrac-
tion. But this so much accelerated motion of the
blood in contracted muscles does not seem to be
merely incidental, but to be arranged by the highest
wisdom of nature, by which, namely, the motive
particles of the blood may be brought in passing to
the motor parts ; and when they have been deposited
from the blood, what remains of it is expelled with a
certain push by the constriction of the shortened
muscle, so that when the loss is repaired, it may again

240 Mayow

return with a new store of motive particles. What
has been said is besides much confirmed by an experi-
ment made by the most ingenious Steno ; for it is
established by his observation that a muscle can by
no means undergo contraction if the artery distributed
to it be tied with a ligature so that the afflux of blood
to the muscle is prevented.

Indeed, I think that the chief use of muscular flesh
is that it may separate from the mass of the blood
certain particles necessary for the contraction of the
muscles. Indeed, we may point out that it is the
function of all kinds of parenchyma to separate by
way of filtration some particles of a definite kind from
the mass of the blood, as is manifest in the paren-
chymata of the liver, ^the kidneys, and others of the
kind. It is therefore probable that the parenchyma
of flesh which is associated with every muscle, has
been constructed in order that by its means particles
of a definite kind, necessary for setting up the con-
traction of muscles, should be filtered out of the mass
of the blood.

But that the structure and use of muscular flesh
may be better understood, let us shortly inquire in
what manner the blood makes its way through the
flesh. For I do not think we should agree with those
who assume an extravasation of the blood. The
special ground for this opinion is that no nutrition of
the parts, so they say, could take place if the blood
were always retained in its vessels, just as a river will
not fertilise the neighbouring meadows unless its
waters flow over its banks to irrigate them. But it
seems scarcely admissible that so confused a thing as
the extravasation of the blood should occur in the
animal economy, where everything is arranged with
such admirable art and order. Besides, I really can-

On Muscular Motion and Animal Spirits 241

not imagine how the extravasated blood could enter
the very minute mouths of the veins ; for if the blood
were diffused through the mass of the muscle it would
seem that the ultimate ramifications of the arteries
and veins would be compressed by the blood surround-
ing them, so that the blood would not be able to enter
the mouths of the veins, as they would be closed by
that compression. Further, it is plain that the blood
is not extravasated in the muscles, because the blood
coming to a muscle does not all rush out if the muscle
is wounded, but this would happen if the blood were ex-
travasated and diffused through the mass of the muscle.

So that as to the transit of the blood through the
muscles it is right that we should hold that the
capillary veins and arteries are united by vessels of
some different kind, so that there is a sort of con-
tinuous passage between them. For I think that the
extremities of the arteries terminate in peculiar
vessels, which, soon after their origin, divide into an
almost infinite number of canals, or rather mem-
branous vesicles, joined here and there by various
anastomoses ; but that the various offshoots of these
vesicles, at last uniting into one canal, terminate in
the gaping mouths of the veins. So that, indeed,
while the mass of the blood wanders hither and
thither through' these tortuous labyrinths, it simulates
extravasation. Further, it is probable that those
passages, or the collection of the said vesicles, exist
separately in each fibre, for in vivisections a cut can
be made in the interstices of the fibres without any
flow of blood, while blood at once flows out when a
fleshy fibre is even slightly wounded.

We may, then, conclude that that collection of
sanguiferous vesicles forms the chief part of muscular
flesh ; for as to the ruddy soHd part of the flesh, that

Q

242 Mayow

seems to be nothing else than an affusion of blood,
which, when coagulated, adheres to these vesicles,
for, while the mass of the blood wanders like the
Mseander among these channels and glides past them
in its placid stream, the thicker particles are deposited
on account of the slackness of the motion, and adhere
to the sides of the vesicles, and yet, if the blood
circulate more quickly, they are carried away with its
impetuous rush, and hence it is that in the heat of
fever and in the more violent exercises, the muscular
parts are despoiled and become lean.

As to the use of the fleshy parenchyma, it is
probable that the aforesaid vesicles, along with the
sanguineous sediment adjoined to them, act as a filter,
by which the motive particles are separated from the
mass of the blood, as we have indicated above. And
it tells in favour of this, that the parenchyma of the
flesh turgid with blood is compressed by the constric-
tion of the contracted muscle and by the natural subsid-
ence of the parts ; whence it comes about that the motive
particles are driven, as it were, by a powerful squeeze
into the motor parts to carry on the function of motion.

As to the nature of the motive particles separated
from the mass of the blood, it is our opinion that they
are of a saline-sulphureous quality. I think, namely,
that sulphureous and saline particles brought to the
highest volatility in the mass of the blood by its
continuous fermentation in the manner elsewhere
described, and most intimately joined together, are
separated from the blood by the action of the
muscular parenchyma and stored up in the motor
parts for setting up their contraction. For we may
note that no small loss of fat takes place in the
more violent exercises, and that it almost wholly
disappears in long-continued hard work ; while yet,

On Muscular Motion and Animal Spirits 243

on the other hand, animals indulging in ease and free
from hard work become very obese, and fat is de-
posited on their muscles in quite sufficient abundance.
Whence we may gather that the sulphureous par-
ticles of the blood, of which the fat is formed, have
some share in the production of muscular contraction.
Indeed, animals seem to be emaciated by hard work
just because the sulphureous and fat particles of the
blood are used up and consumed in muscular con-
traction, while yet if the motor parts have long ceased
from contraction the sulphureous particles are not now
spent in producing the contraction of the fibrils,
but are carried away through special vessels into
suitable receptacles and, brought there in sufficient
abundance, constitute fat. But that the fatty par-
ticles are carried by special vessels, is proved by the
fact that the blood-vessels disseminated through the
mass of the muscle do not extend to the fat connected
with almost all muscles, so that the sulphureous
particles composing the fat cannot come immediately
from the blood, but they must be brought by special
vessels from the inner part of the muscle ; and
certainly it has been established by anatomical obser-
vation that certain membranous vessels dispersed here
and there through the mass of the fat are continued
into the inner parts of the muscles. It does not
seem likely that the fat thus stored in appropriate
receptacles returns to the motor parts, still it is not to
be by any means regarded as a useless excrement, but
as serving various ends, such as the support of delicate
parts and the lubrication of others. But these things
will be discussed more at length later. In the
meantime let us inquire as to the nature of the
animal spirits, the influx of which into the muscles is
also necessary for bringing about their contraction.

244 Mayow

CHAPTER IV

THE ANIMAL SPIRITS BY WHICH MUSCULAR CON-
TRACTION IS PRODUCED CONSIST OF NITRO-
A ERIA L PAR TICLES. I NCI DENT A LLY, AS TO THE
MOTION OF THE BRAIN

As to the nature of the Animal Spirits, we may
conclude that they, so far at least as they contribute
to animal motion, consist of Nitro-aerial Spirit. But
that this may be more clearly understood, let us first
suppose that nitro-aerial particles, which we have
elsewhere shown to be passed into the blood by
respiration, have also some share in setting up the
performance of motionj as has long been our opinion.
For, indeed, we have remarked a good while ago, in
our Treatise on Respiration, that animals in the more
violent exercises, as when much urged in running,
find of all things a necessity of very much increased
respiration ; and the cause of this seems to be, that in
violent movements the nitro-aerial particles are separ-
ated from the mass of the blood to set up the contraction
of the muscles and are used up, so that there is need of
more frequent respiration by which the blood may
repair its losses, and have restored to it anew nitro-aerial
particles for carrying on the function of motion. For
the purpose of the increased respiration in violent exer-
cises is not that the blood coming in greater abundance
to the central organs and pushed on by the more fre-
quent collapse of the lungs, should pass through them
more easily ; for in febrile heat, when, namely, the
blood circulates in a most furious whirl, the respiration
is nevertheless no more intense than usual : indeed,
it has been elsewhere shown that the blood can pass

Oil Muscular Motion and Animal Spirits 245

through the lungs although they do not move. Nor
is it, as some one might say, that respiration is
increased in violent exercise to cool the heated blood,
for it would follow from that that in febrile heat,
when the blood is as it were on fire, there would also
be need of more intense respiration. And, moreover,
we have shown above that inspired air tends rather to
the heating than to the cooling of the blood, so that
it should rather be said that by the contraction of the
muscles, often repeated in violent movements, the
blood is deprived of fermentative particles and in
some measure coagulated ; and that there is need of
more intense respiration for this reason, namely, that
the loss of the fermentative particles being again
repaired, suitable fermentation may be excited in the
blood. Hence, indeed, it follows that the nitro-aerial
particles, upon which the fermentation of the blood
depends, are separated from the mass of the blood in
violent movements, are spent in the contraction of
the muscles, and are lost.

From what has been said, we conclude that nitro-
aerial particles are necessary for the performance of
muscular contraction, and this will be still more
manifest from what follows.

I think it must be conceded that the motion
of the muscles is brought about by particles of
different kinds mixed with one another, for indeed I
cannot imagine how else animal motion could be
produced. For as to elasticity and weight, by which
automata are set in motion, neither of them can have
a place in the animal structure, inasmuch as motion
produced by them would soon come to an end.
Therefore it seems that we must conclude that the
motive function is effected by particles of different
kinds, mixed together, on the determination of the

246 Mayow

mind, and mutually agitated in most rapid motion.
And this is further confirmed by this, that for the con-
traction of the muscles there is, as we have indicated
above, absolute need, not only of animal spirits,
brought by the nerves from the brain, but in addition,
of other particles supplied by the blood.

Let us now consider, then, what is the nature of
those particles by means of which muscular motion is
effected. As to this, the most commonly accepted
opinion is that muscular motion depends upon salts
of different kinds, mixed together and mutually effer-
vescing in the motor parts. For indeed it is neces-
sary for setting up effervescence of this kind, that one
of these salts should be of an acid character, but the
other purely saline, fixed or volatile ; but it is indeed
probable that an acid salt never exists in the mass
of the blood except in case of disease, inasmuch
as, when in a state of health, it is impregnated only
with volatile, or it may be acido-saline salt, such as
the ammoniacal salt. Besides, it is scarcely to be sup-
posed that an acid salt has a place in the motor parts,
because all acids are directly hostile to the tender
and delicate structure of the fibrils, and they would
be much injured by an acid liquid poured on them.
Furthermore, when these opposed salts, of whatever
sort they be, come from the mass of the blood, what
would prevent them, mixed in the blood, from acting
on each other, and, as contrary salts do, destroying
each other ? And to these considerations we may
add that the effervescence of contrary salts would not
by any means be suitable for the motor parts, inas-
much as contrary salts mixed together do not com-
bine without coagulation, but yet coagulation can by
no means be admitted in the very minute structure of
the fibrils. Nor should we omit to notice this, that

071 Muscular Motion and Animal Spirits 247

the effervescence arising from the meeting of contrary
salts takes place only slowly, and usually lasts for some
time, and that this does not agree with the instan-
taneous contraction of the muscles, as we have indi-
cated above.

So that for effecting the contraction of the muscles
there is required an excitement of the elastic particles,
of a kind that can be accomplished instantaneously
and without any sort of coagulation. And indeed I
do not know if there be in the nature of things any
other such fermentation but the singular case of the
effervescence of nitro-aerial and saline-sulphureous
particles, which mutually, as their nature is, excite
themselves to a most rapid motion. We must there-
fore conclude that it is from that that muscular con-
traction proceeds. And if the one set of motive
particles, as I have tried to show above, are of a saline-
sulphureous nature, it is most necessary that the other
set of motive particles should be of the nitro-aerial
kind, inasmuch as these alone are by their nature fitted
for exciting the saline-sulphureous particles.

I think it has been established from what has been
elsewhere said, that nitro-aerial and sulphureous
particles effervesce when mixed with one another, but
to these evidences the following experiment may be
added. If, namely, the most highly rectified spirit of
wine be mixed with spirit of nitre deprived of its
moisture, a conspicuous heat will presently be pro-
duced, at all events if the mixture be slightly warmed ;
and the explanation of this seems to be that the
nitro-aerial particles (which we have elsewhere shown
to abound in the spirit of nitre) and the very volatile
saline-sulphureous particles of which the spirit of wine
consists excite one another to motion, as is their
nature, for it must not be supposed that the spirit of

248 Mayow

nitre, as far as its saline and acid part is concerned, is
in any way opposed to the sulphureous particles of
the wine.

For, no doubt, just as the nitro-aerial spirit meeting
with terrestrial sulphur excites that fermentation in
which the motion and the life of vegetables consist,
so also according as the same spirit, brought by means
of respiration into the mass of the blood and there
effervescing with the saline-sulphureous particles of
the blood, produces the vital heat and motion, as I
have elsewhere striven to show, it is probable that
animal life and the motive function are brought about
by the same particles more exalted and put in a
condition of the highest vigour. For indeed I think
that the nitro-aerial particles springing forth from the
brain into the motor parts effervesce there with
the saline-sulphureous particles meeting them, and
muscular contraction is caused by their mutual agita-
tion in the way to be stated below. And hence it is
that for keeping up animal motion it is essentially
necessary that there should never be a deficiency in
the mass of the blood of saline-sulphureous pabulum or
of nitro-aerial particles ; and by how much more
intensely the muscular contraction takes place, as in
the harder kinds of work, so much greater is the outlay
of nitro-aerial and of sulphureous particles, for the
repair of which not only is the respiration increased,
but besides there must be taken in greater quantity
food filled with saline-sulphureous particles. Hence
those articles of food which contain abundance of
volatile salt and sulphur are specially fitted for restor-
ing the powers worn by long-continued labour.

From what has been said, we may seek the reason
why so intense a heat is excited in the motor parts by
violent exercise. That heating is commonly attri-

On Muscular Motion and Animal Spirits 249

buted to the motion of the body itself, but indeed in
animal motion there is no such friction of the parts
(from which alone heat arises) as could account for so
intense a fervour. We must, therefore, believe that
the heat of strongly contracting muscles comes from
nitro-aerial particles, at that time much agitated in
the muscles ; as I have endeavoured elsewhere to
show that every kind of heat arises from their
motion.

I may here note by the way that the ancients, not
altogether without reason, supposed that the source
of vital heat was in the heart ; not that a sort
of Biolychnium, whatever that may be, constantly
flamed in its sacred cloisters, but that, inasmuch as
the heart is unweariedly at work in continuous labour
for keeping up the motion of the blood, the nitro-
aerial and the sulphureous particles effervesce con-
tinuously in its muscular part, and that by their
motion a notable heat must be produced.

Further, from the foresaid hypothesis a reason
can be deduced why the sweat given out in violent
movements is of a saline character, and very penetrat-
ing. For the extremely subtle nitro-aerial, as also
the saline-sulphureous particles, by which when mixed
together the contraction of the muscles is produced,
when forced out along with the serous liquid, render
it acrid and very penetrating. The reason why the
sweat is acido-saline seems to be that the volatile salts
of the blood, intimately combined with sulphureous
particles, are partly brought to a liquid state by the
effervescence which takes place in the muscular
contraction, in the way elsewhere described.

From what has hitherto been said, it is to some
extent proved that muscular motion depends on
nitro-aerial and saline-sulphureous particles mutually

250 Mayow

moving themselves in the motor parts. But now of
these particles by which muscular contraction is pro-
duced, some, viz. the animal spirits, are brought into
the motor parts from the brain by means of the
nerves ; while others are supplied from the mass of
the blood ; as we have shown above. Let us now see
whether the nitro-aerial particles are those motive
particles supplied from the blood, or, on the other
hand, are those coming from the brain — that is, the
animal spirits. On this point I was for some time
in doubt whether the nitro-aerial particles go im-
mediately from the blood into the motor parts ; but
on serious consideration of the matter it seems more
probable that the motive particles supplied from the
blood are of a saline-sulphureous kind, as to some
extent appears from what has been said above :
whence it follows that the nitro-aerial particles come
from the brain, and consequently are themselves the
animal spirits. Indeed, it is much more probable that
the nitro-aerial spirit should come from the brain
than that saline-sulphureous particles should do so.
For sulphureous particles do not occur at all in the
brain, whereas they are disseminated everywhere
throughout the mass of the muscles. Indeed, sul-
phureous matters seem to be hostile to the animal
spirits ; for, liquors full of volatile sulphur, such as
spirit of wine and the chemical oils of vegetables,
when taken too quickly disturb the brain and
the animal spirits, and produce not only drunken-
ness, but not rarely madness and fatal convulsions.
While on the contrary the structure of the brain
seems to be such as to render it specially fit for
separating the nitro-aerial spirit from the blood and
for preserving it, as will be more fully stated below.
As to the nature of the animal spirits, the authority

On Muscular Motion and Animal Spirits 251

of the learned Dr Willis had no small weight with
me ; he supposes that the animal spirits are of the
nature of volatile salt. For this learned man in his
treatise on Diseases of the Brain^ chapter xi., speaks
as follows : Aiid indeed the Animal Spirits when in a
healthy and regular condition seem, to behave to some
extent as a spirituous liquor full of volatile salt which
distils from the blood. But, indeed, with all respect to
so eminent a man, since muscular contraction is pro-
duced by particles of diverse kinds mixed together
and mutually moving themselves (as is the view of
the learned author, and as also seems most consonant
with reason), if the animal spirits consist of volatile
salt, then the other motive particles supplied by the
blood must be acid salt, for otherwise the animal
spirits meeting them would not effervesce : but it is
scarcely to be supposed that acid salt can have a
place in a healthy body, much less in the motor parts,
as has been shown above. Should we admit that an
acid liquid is contained in the fibres, why should not
the animal spirits effervescing with it sometimes them-
selves turn into an acid liquid, as does happen, accord-
ing to the learned author's opinion, in Melancholia
and Mania? Wherefore it seems preferable to sup-
pose that the animal spirits consist of nitro-aerial
particles, which proceeding, on the determination of
the mind, from the brain into the motor parts, meet
there the saline-sulphureous particles, and that by
their mutual agitation taking place according to their
nature, the contraction of the fibrils is effected in the
way to be described below. Indeed, I imagine the
animal spirits to be of such a sort that they never
undergo change ; and as to the diseases which are
commonly believed to depend on their vitiated condi-
tion, I consider that they arise from the interrupted

252 Mayow

flow of the animal spirits or from their inordinate
motion, as will be more fully stated below.

For, indeed, nitro-aerial particles seem in a high
degree to fit the character of animal spirits, inasmuch
as they are very subtle, elastic, and agile. For nitro-
aerial particles are suited for entering on very rapid
and igneous motion, as we have elsewhere shown.
The animal spirits are also of this sort : they pass in a
moment through the filaments of the nerves, although
these have no visible cavity ; and brought at last to
the muscles, cause their instantaneous contraction by
their own most rapid motion.

Further, the animal spirits, like the nitro-aerial
particles, are so slender that they are at once dissi-
pated and leave no vestige of themselves. I further
add that nitro-aerial particles, no less than the animal
spirits themselves, are necessary for the sustenance of
life. In fact it is difficult to conceive why animals
should have such a necessity of breathing air, so that
not for a moment can they live without it, unless
the nitro-aerial spirits had a primary place in animal
life and were the animal spirits themselves. Hence,
according as there is need of a greater abundance of
animal spirits, as in violent movements, or of less, as
when the body is at rest, so nitro-aerial particles must
be supplied in greater or in less quantity, and this is
the reason why the respiration is so much increased in
violent movements.

Besides, whence, I would ask, is a supply of animal
spirits sufficient for continued work obtained unless^
I say, we call to our aid the air, that inexhaustible
fountain ? For it is probable that animal spirits are
used up in the performance of muscular contraction
in much greater quantity than is commonly believed.
For I really do not know how a muscle could contract

On Muscular Motion and Animal Spirits 253

itself with so much force, unless elastic particles were
present in sufficient abundance for its contraction ;
and hence it is that in violent exercises the respira-
tion is so much increased that the great expenditure
of animal spirits made in motive effort may be re-
paired.

And not only for muscular motion but also for
sustaining life itself, it seems that there is need of an
ample supply of animal spirits ; for it is probable that
life cannot be sustained without a certain series and
continuous flow of animal spirits passing constantly
through the brain, or at all events through the
cerebellum. And that is the reason why, if the
respiration or the motion of the heart or of the blood
be stopped even for a moment, the animal at once
dies. But more fully of this below.

In confirmation of what has been said, there may be
adduced what the learned Malpighi has observed as
to the Respiration of Insects : viz. — Insects which live
when their head is cut off^ and the separated portions of
which live^ have pneumonic vessels distributed through
the whole duct of their spinal m,arrow. For this
eminent man observed that the black points which are
to be found on each side of insects close to the spine,
are so many spicula or tracheae through which the
insects draw air ; insomuch that if the said spicula be
smeared with oil the animal soon dies from want of
breath. Further, he found out that some branches of
the said tracheae are inserted here and there into the
spinal marrow.

But that we may apply these observations to the
present subject, I think we must allow that the
animal spirits in the more perfect animals are elabor-
ated only in the brain, and that they are dissemin-
ated from that source to the spinal marrow and to

2 54 Mayow

the nerves originating in it ; whence it comes about
that if the head of such animals is removed, the
influx of animal spirits into the spinal marrow is
altogether shut off, so that the parts of the decapi-
tated body at once collapse and are deprived of
animal motion.

But in less perfect animals, such as insects, whose
cut-off parts live, the animal spirits are primarily and
immediately prepared, not only in the brain but also
in the protuberances of the spinal marrow, as it
were in so many cerebelli extended through the
whole length of the spinal marrow, or rather they are
stored as in suitable repositories ; and hence it comes
to pass that in the cut-off portions of insects, the
animal spirits are supplied, for keeping up to some
extent life and motion, from the small piece of spinal
marrow connected with each portion.

But that the animal spirits should be brought into
the spinal marrow of insects, it is most necessary that
some spiracula or bronchiae should be, as is the case,
continued into it, so that nitro-aerial particles, of
which animal spirits consist, should by their means be
carried into the spinal marrow. Hence, if any of the
said spiracula be smeared with oil, the neighbouring
parts, inasmuch as they are deprived of nitro-aerial
particles and of animal spirits, at once become para-
lysed, the remaining parts being meantime healthy ;
while yet in perfect animals the nitro-aerial particles
are introduced into the blood only through the lungs,
and then, by the heart's pulsation and the flow of
the blood, are carried to the brain and thence to
its spinal appendix. Hence it happens that if the
trachea is obstructed, and inspiration suppressed, or if
the motion of the heart and of the blood stops, or
even if the brain is disordered, the nitro-aerial particles

On Muscular Motion and Animal Spirits 255

will not be transmitted to the brain for the prepara-
tion of animal spirits, and therefore the animal will
speedily die.

From these things I conclude that it is to some
extent made out that nitro-aerial particles, transmitted
by means of respiration to the mass of the blood and
thence to the brain, are the animal spirits themselves.
And this is in accordance with the fact that animals
placed in a glass vessel from which the air is exhausted
by means of Boyle's air-pump, after a short time
perish miserably in convulsions. For the animal
spirits being deprived, by the removal of the air, of
their due supplement, enter, as is their wont, upon
disorderly movements, and rushing tumultuously into
the nervous system, excite convulsive movements,
and at last the animal dies for want of air and of
spirits.

To these things I further add that those who suffer
from English consumption are very much weakened
and are almost destitute of animal spirits. And the
reason of this seems to be, that as their lungs are
wasting and flaccid, the nitro-aerial spirit is no longer
brought to the mass of the blood in quantity sufficient
for the preparation of animal spirits.

Nor should it be overlooked that in pestilential
diseases the brain chiefly suffers, and the economy
of the animal spirits is disturbed : for in so far as, in
the spread of the plague, the nitro-aerial spirit is
tainted by the poison, it must follow that the animal
spirits, composed of it, are out of sorts.

At any rate nitro-aerial particles seem to be in the
highest degree suitable for the preparation of animal
spirits ; for it is the nature of spirits to be sometimes
inert and languid, and indeed on the other hand
sometimes very active and agile. Similarly the nitro-

256 Mayow

aerial spirit is wont to assume diverse states, for at
one time it is in the most complete rest, and at
another with its greatest agility it enters on most
excited motion. For nitro-aerial spirit, when mixed
with sulphureous particles, is moved with most rapid
and sometimes quite igneous motion ; but when
loosed from the company of sulphureous particles,
it attains a state of extreme quiet, as we have else-
where shown.

Lastly, let us here note that the nature of the
brain seems to fit it in a high degree for collecting
and storing nitro-aerial particles, as the brain in
comparison with other organs lacks the sulphureous
particles which agitate and waste the nitro-aerial
spirit ; and that it has a sort of saline quality which
specially fits it for retaining the nitro-aerial spirit.

From this hypothesis of ours the reason may be
sought, why, above all other sensibles, light affects
the animal spirits, and, by exciting them to motion,
produces wakefulness, so that to induce sleep animals
must close their eyes and so shut out the external
light, while yet to the other sensoria the way lies
open for external objects even in sleep. For I have
elsewhere tried to show that light depends on the
motion of nitro-aerial particles disseminated through
the air. Therefore, as animal spirits consist of nitro-
aerial particles, it comes to pass that they easily
follow the motion of the luminous particles which are
of the same kind as themselves. It tells also in the
same direction that the eye, when struck with a pretty
strong blow, seems to see a flame in front of it. For
it is probable that the nitro-aerial particles, thickly
occupying the optic nerves, are excited by the violent
concussion to the motion requisite for the production
of light. But whether some animals, such as the cat,

On Muscular Motion and Animal Spirits 257

can, at their own will, give a luminous motion to the
nitro-aerial spirits in the eye, I cannot certainly
decide : it is so far an indication of this that the cat
can use its sense of vision even in the dark.

It is in harmony with the hypothesis stated above
that animals struck by lightning are not unfrequently
killed without any injury, or vestige of a blow. But
that the reason of this may be understood, I may
repeat here what I have elsewhere endeavoured to
show, viz., that lightning is caused by the nitro-aerial
particles diffused through the whole atmosphere being
thrown by the violent concussion of the air into a
luminous, and sometimes really igneous motion.
Wherefore, if nitro-aerial particles constitute the
animal spirits, it may sometimes happen that they
in the brain follow the motion of the nitro-aerial
particles forming the lightning in the air ; so that
the animal spirits would seem not so much struck
by lightning as themselves to form lightning. And
hence it is that they, being violently moved and as it
were set on fire, are dissipated in a moment ; and so
on account of the flame kindled in its brain the
animal, deprived of the common light and breath,
is extinguished. But this will be dealt with later.

We may note here in passing that animals have
need of more intense respiration for some time after
violent exercise. The reason of this seems to be that
the blood returned from the brain to the heart is to a
great extent deprived of nitro-aerial particles, inas-
much as it had deposited some in the brain and in
the cerebellum to supply animal spirits ; whence it
comes about that no small part of the blood goes
without its proper fermentation, because of the lack
of nitro-aerial particles, and is to some small extent
coagulated. For it has been elsewhere shown that

R

258 Mayow

the fermentation and the motion of the blood are
caused by nitro-aerial particles. And this has also
been noted by the learned Dr Thruston. Where-
fore, for the proper fermentation and fluidity of the
mass of the blood there is need of a more frequent and
a fuller respiration, even for some time after violent
movement. And from these things we may seek the
reason why the blood drawn during convulsive
paroxysms is usually very thick and somewhat
grumous. For in more violent muscular contraction
there is very great expenditure not only of nitro-aerial
but also of saline-sulphureous particles (as it is on their
mutual action that the fermentation and fluidity of the
blood depend), and therefore the mass of the blood
must to some small .extent be coagulated. But this
is especially the case when the parts which serve for
respiration suffer convulsion ; for then, on account of
the nearly suppressed respiration, the loss of nitro-
aerial particles caused by the convulsive movements
is not, as in other cases of violent movements, repaired
by respiration.

One might at first sight object to what has been
said above, that the animal spirits form a chief part
of the body, and that it is therefore likely that they
should be derived not from the air, as being something
external and foreign to the body, but rather from the
nobler particles of the blood, when these have been
brought to the highest subtlety and vigour : further,
that it does not become the admirable artifice of the
animal mechanism that it should be set in motion by
an external principle. I reply that, of whatever sort
the animal spirits may be, they must certainly be
supplied from without. For that they should be
formed from the blood, as the mass of the blood is
daily renewed from food, spirits even arising from

On Muscular Motion and Animal Spirits 259

that would come from without. Why, then, should
the animal spirits not rather be derived from air than
from food taken in ? Undoubtedly the air is im-
pregnated with most active and subtle particles ; and
there is such a necessity of inhaling it that not for a
moment can we live without it. And indeed it does
not seem possible that the immense expenditure of
animal spirits can be supplied from any other source
but the air.

But as to the artifice of the animal mechanism,
it consists in this, that the parts of the body are
formed with such perfect adjustment that quite
stupendous effects are produced in it by common
causes.

I may note here, by the way, that while I hold that
nitro-aerial particles are the animal spirits, I do not
wish to be so understood as if I thought nitro-aerial
spirit to be the sensitive soul itself: for we must
suppose that the sensitive soul is something quite
different from animal spirits, and that it consists of a
special subtle and ethereal matter, but that the nitro-
aerial particles, i.e.^ the animal spirits^ are its chief
instrument. For, indeed, as to the sensitive soul, I
can form no other notion about it than that it is some
more divine aura^ endowed with sense from the first
creation and co-extensive with the whole world, and
that a little portion of it, contained in a properly
disposed subject, exercises functions of the kind which
we observe and admire in the bodies of animals ; but
that that spiritual material, existing out of the bodies
of living things, is not to be supposed either to
perceive or to do anything but to lie quite dormant
and inert, being much as is the case with the sensitive
soul when the animal is buried in sleep.

The afflux of arterial blood does not seem sufficient

2 6o Mayow

by itself for bringing the nitro-aerial spirits to the
brain in ample enough quantity : wherefore I consider
it likely that the thicker menmges which surrounds
the brain undergoes a sort of pulsation, and that by
its contraction the blood driven to the brain is
compressed ; and that thus the nitro-aerial particles
are pressed out of the mass of the blood, and driven
into the brain, in a way not very unlike that in which
the other motive particles are forced into the motor
parts by the constriction of the muscles. Such a
pulse of the dura mater is confirmed by autopsy
itself: for, in fracture of the skull, part of the brain
comes into view, it is seen to rise in a tumour, and
immediately in turn to subside, which seems to be a
motion of the brain after the manner of the heart's
pulsation. For, indeed, when I consider the thickness,
the strength, and the nervous fibres of the dura mater ^
I can imagine nothing else than that that membrane,
like all the others, is intended for the production of
motion. For it is probable that the dura mater
behaves as another diaphragm by the help of which
the brain draws in nitro-aerial spirits and in a sense
breathes.

It is probable that the above described motion of
the meninges is natural, but yet that we can at will
increase its pulsation, just as we can that of the parts
which serve for respiration. And so by its diverse
motion various effects are produced in the bodies of
animals, as is probable. For according as that mem-
brane contracts itself more strongly or more weakly,
the nitro-aerial particles, i.e.^ the animal spirits, are
driven in greater or in less abundance into the brain
and thence into the nervous system. Hence if a
supply of animal spirits greater than usual is required
for carrying on more intensely the motive or the

On Muscular Motion and Animal Spirits 261

sensitive function, we need to constrict the head and
brain, as any one can find out in his own case : and
that constriction of the brain seems to proceed to
some extent from the harder meninges contracting
itself more strongly. Certainly, in great anger, when
we strive to the utmost of our power to repel or to
avenge an injury, the said membrane, as if seized
with convulsions, seems to constrict the brain :
whence it happens that the nitro-aerial spirits, forced
into the brain and thence into the nervous system,
produce certain involuntary movements and con-
vulsive tremors.

I further add that it is probable that sneezing is
produced by the dura mater contracting itself more
strongly, and forcibly driving the animal spirits into
the nerves devoted to respiration ; for it is certainly
established that the membranes of the brain are
primarily affected in sneezing.

Further, I am not sure whether the pulsation of the
heart, or even the respiration, both of which are
periodic, do not depend on the pulsation of the harder
meninges surrounding the cerebellum.

Further, it may be held that epilepsy, as also
apoplexy, sometimes arise from the convulsion or
from the paralysis of the said membrane : for in these
diseases the brain itself is sometimes found free from
any sign of disease, and those substances which consist
of volatile salt and volatile sulphur, as oil of amber
and such like, are specially useful in these diseases :
for it is not to be supposed that the saline-sulphureous
liquids penetrate the brain itself and strengthen it,
inasmuch as sulphureous substances seem to be
hostile to the brain, and when taken too quickly, rushing
into the cloisters of the brain not unfrequently cause
convulsions, as we have elsewhere indicated. But

262 Mayow

we may believe that the reason why the said oils are
useful in these diseases is because they are specially
suitable for strengthening the motor parts and the
nervous fibres. For it has been found by experience
that those things which consist of volatile salt and
volatile sulphur are specially suitable for restoring the
fibres of the muscles to a proper tone. Whence it
comes that medicaments of that sort bring help to
the weakened and all but broken membranes of the
brain, and consequently afford very great aid in the
above-mentioned diseases.

But, to go a little further in our conjectures as to
the use of the said membranes, it seems probable that
sleep is caused by the membranes surrounding the
brain, but not those surrounding the cerebellum, either
ceasing from their motion or at all events performing
it but remissly, so that the nitro-aerial particles are
no longer carried into the brain, and thus the animal
functions are necessarily interrupted. For that a
need of sleep presses upon animals wearied with
labours is not, we must suppose, because of a want of
nitro-aerial particles, i.e,^ of animal spirits, inasmuch
as a never-to-be-exhausted stock of them exists in the
air, but rather because the saline-sulphureous particles
of the blood have been consumed by watching and
work ; but the deficiency of saline-sulphureous particles
concerns the motor parts but not the brain, except in
so far as the meninges of the brain, which are to be
reckoned among the motor parts, refuse to perform
their pulsations if there is a want of saline-sulphureous
particles in the blood. Wherefore it would seem that
we should hold that sleep takes place because the
saline-sulphureous particles are so much consumed by
work and watching that, on account of their deficiency,
the meninges of the brain refuse to perform their

On Muscular Motion and Animal Spirits 263

movement. It certainly seems to have been arranged
by the good providences of nature that when the
saUne-sulphureous particles are nearly exhausted by
vigils, what remains of these particles should be
reserved for the natural functions — those really
necessary for life. Hence it is necessary that the
membrane surrounding the brain should sometimes
cease from its motion, so that the small remaining
portion of motive particles should be employed for
the motion of the membrane surrounding the cere-
bellum, and the other natural functions. For it nmst
he noticed that although the spontaneous animal
functions which are performed by means of the brain
are for a time interrupted during sleep, yet the function
of the cerebellum and the natural motions go on no
less, nay, rather better, when we are asleep than when
we are awake.

It goes to confirm what has been said, that when
we have recently awakened from sleep we feel our
brain turgid with blood and somewhat heavy. The
reason of this seems to be that in sleep, the membranes
of the brain ceasing from their pulsation, the motion
of the blood is not promoted by the contraction of
the said membranes as when one is awake, and there-
fore the blood must be somewhat detained, and
stagnate in the membranes of the brain. Buc mean-
while during sleep the arterial blood, its passage
through the brain being to some extent obstructed,
is carried in greater abundance to the cerebellum ;
hence the nitro-aerial particles pass in sleep in greater
abundance to the cerebellum and the nerves arising
from it, and thus it is that the natural functions
presided over by the cerebellum are better performed
in sleep than when one is awake. What has been
said also gives us a reason why, in diseases character-

264 Mayow

ised by sleepiness, rather remiss respiration suffices for
sustaining life. For in these diseases the respiration
seems quite suppressed, and the wretched patients
have not unfrequently been buried for dead. For as
in such diseases the nitro-aerial particles are carried
to the cerebellum only, and thence to the nerves
dedicated to the natural functions, and even then
natural offices are very remissly performed, it follows
that the expenditure of nitro-aerial particles is the
very smallest, and that for the reparation of this the
least trace of respiration suffices.

CHAPTER V

OF THE FERMENTS OF THE STOMACH, THE PAN-
CREAS, AND THE SPLEEN. INCIDENTALLY, OF
DISEASES WHICH HAVE REFERENCE TO THE
ANIMAL SPIRITS

From this hypothesis of ours it is possible conveniently
enough to explain not only the effervescence set up
in the motor parts, but also how the fermentations
and concoctions of whatever sort are carried on in
the viscera of animals.

For, in the first place, as to the digestion made in
the stomach, the vulgar opinion is that there is in
the stomach a certain acid ferment. But whence
that acid should derive its origin one cannot very
readily say, for anatomical observation establishes
that no acid at all resides in a healthy stomach ; and
as to acid eructations, they seem to come from ill-
digested food and not from any natural acid liquid.
We havC; then, to inquire how it comes about that
iron filings, taking in by the mouth, are corroded in
the stomach and turned into a sort of vitriol ; and

On Muscular Motion and Animal Spirits 265

after taking chalybeate drugs a sulphureous and
vitriolic odour is perceived in the throat, such as
is usually produced from iron corroded by an acid
liquid. Further, milk is coagulated in the stomach
as it is when an acid liquid is added to it, and food
when eaten not unfrequently becomes sour.

As to these things, I shall in the first place
assume that the digestion of food is effected by the
animal spirits, brought by means of the nerves, of
which there are many inserted in the stomach, and
that according as the animal spirits come to the
viscera which serve for digestion in greater or in
smaller abundance, so the digestion of the food is
accomplished more quickly or more slowly. Hence
if any one soon after a meal sets himself to study,
or thinks much upon a difficult subject, so that the
animal spirits are to a great extent detained in the
brain on account of strained contemplation and
greater agitation of the mind, the function of
digestion is not properly performed on account of
the deficiency of animal spirits ; but the undigested
food remaining in the stomach produces heaviness
and discomfort there, as anyone can observe in
his own case. Yet, on the other hand, when
the mind is free from thought, or even in sleep, the
concoction of food goes on at the best ; that is to
say, in so far as the animal spirits, not being engaged
in carrying on other functions, are abundantly
supplied to the viscera devoted to digestion. This is
also indicated by the fact that soon after a rather
full dinner or supper we usually have an inclination
to sleep. For, indeed, when the stomach is replete
the animal spirits for the greater part retire to the
cerebellum and thence to the lower part of the
abdomen to carry out the office of coction, so that

266 Mayow

scarcely any remain in the brain to perform the
voluntary functions and sensation, whence it is that
we can hardly keep awake.

But, now, as the animal spirits consist of nitro-
aerial particles, there will be no difficulty in under-
standing how the effects just described are produced
by them in the stomach. For although the nitro-
aerial spirit is not acid, still iron is corroded by it
and vitriols produced, fixed salts are liquefied, and the
structures of things are dissolved as by a universal
solvent, as I have elsewhere endeavoured to show.
It therefore seems established that the much-talked-
of ferment of the stomach consists chiefly of nitro-
aerial particles, which, deposited in the membranes
of the stomach by the nerves, are probably there mixed
with a suitable liquid secreted from the blood by
means of the glandular membranes of the stomach ;
and that the fermentative liquid of the stomach is
composed of both of them brought into its .cavity
by special vessels. And hence we may seek the
reason why serene and rather thin air so much tends
to sharpen the appetite and to promote digestion,
as has been found by common experience, while
when the air is thicker and loaded with noxious
vapours it soon produces discomfort in the stomach.
To these I further add, that from the swimming-
bladder which in many fishes has been found filled
with an aerial substance, there is an open passage
into the stomach — certainly a probable indication
that something aerial conduces to the digestion of
food, as has been remarked by the learned Dr Walter
Needham. Indeed, as fishes take only a small
quantity of air out of the water, it would seem
necessary that the aerial ferment should be stored in
some receptacle from which it may be brought in

On Muscular Motion and Animal Spirits 267

sufficient abundance when required. I am not able
to decide certainly whether in terrestrial animals
also, besides the nitro-aerial spirits brought by the
nerves, an aerial ferment may not in addition come
into the stomach directly from the mass of the
blood.

I conclude that the digestive liquid of the stomach
is not very different in kind from saliva ; for saliva
seems to consist of nitro-aerial particles deposited in
the maxillary glands by the nerves and there mixed
with a serous juice derived from the blood : and that
it is to be believed that the saliva mixed in mastica-
tion with the food conduces not only to its deglutition
but also in no small degree to its digestion.

If the stomach be quite empty of food, its internal
membranes are, as is probable, pinched by the
nitro-aerial particles, and hunger seems to arise from
this.

The food is concocted by the ferment of the
stomach into chyme, which, when it has passed into
the duodenum immediately meets the bile, by which,
as by a new ferment mixed with it, it is further
fermented and concocted. For as the bile is com-
posed of saline-sulphureous particles, it necessarily
effervesces in a high degree with the chyme, which
is full of nitro-aerial particles ; but to what ex-
tent bile partakes of a fermentative nature may
be gathered from this, that if it is mixed with a
farinaceous mass it raises it and ferments it, as has
been elsewhere stated.

OF THE FERMENT OF THE PANCREAS

I think that the pancreas must also be counted
among the viscera serving for digestion, inasmuch

268 Mayow

as it is probable that the nerves which are distributed
in great number in the pancreas, serve for carrying
nitro-aerial particles, which, finding a suitable vehicle
secreted by its glands from the mass of the blood,
are passed into the duodenum by the duct of Vir-
sungus for the further fermentation of the chyme.
For when that pancreatic liquid, full of nitro-aerial
particles, meets the chyme, imbued with bilious, that
is, saline-sulphureous particles, a very intense effer-
vescence must be excited ; and it is probable that
by means of this the concoction of the chyme is
completed.

After these remarks as to the viscera had been
written, a treatise on the pancreatic juice published
by the eminent Regner de Graafc2iVCiQ into my hands,
in which that learned man most clearly proves the
existence of the pancreatic juice, and confirms the
use which I have assigned to it. But it is scarcely
credible that healthy pancreatic juice is of an acid
nature : nor is it likely that the effervescence taking
place when that juice is mixed with bile in the
intestines is caused by the acid salt of the pancreatic
juice meeting the fixed or the volatile salt of which
the bile consists, as is the opinion of the learned
author ; for the effervescence of contrary salts does
not seem suitable to the animal economy inasmuch
as it comes quickly to an end and is always ac-
companied by coagulation, as has been stated above.
Further, any acid salt mixed with a saline-sulphureous
liquid changes and destroys its saline-sulphureous
particles and coalesces with them into an, as it were,
dead and insoluble calx, as in the preparation of
lac stUphuris^ as also happens in the case of bile
mixed with an acid liquid. And hence it is that acid
salts are most suitable for allaying inordinate fermen-

On Muscular Motion and Animal Spirits 269

tation of bile. While yet, on the contrary, in the
natural fermentation excited in the intestines, the
saline-sulphureous particles are brought to a just
volatility, as appears from the fetor of the dejections
and the inflammability of the flatus escaping from
the belly. Wherefore it is probable that the effer-
vescence produced when the bile and the pancreatic
juice are mixed together, arises from the working of
the nitro-aerial particles contained in that juice with
the saline-sulphureous particles of the bile, which
fermentation is fitted to exalt the saline-sulphureous
particles of the bile, as we show elsewhere.

OF THE USE OF THE SPLEEN

Let us now, lastly, draw from this hypothesis of ours
a conjecture also as to the use of the spleen. If we
consider the wonderful structure of the spleen and
its notable size, and further regard the numerous
branches of nerves devoted to it, and its immense
supply of blood, we shall certainly conclude that the
spleen (which is to be found in all animals) serves
some general purpose. But it is an astonishing thing
that animals can live although their spleen is com-
pletely extirpated, and indeed bear its loss without
any manifest inconvenience. Hence there has been
much discussion among anatomists as to the function
of the spleen ; so that it might seem that this
troublesome organ had been made to harass the
minds no less of the physician than of those suffering
from it. For, indeed, nature has covered the spleen
more than other parts with blackness and darkness,
as if she wished to hide it and keep it in the dark.
Some have assigned to it a use so frivolous and mean,

270 Mayow

that the indignant spleen could scarcely but burst
itself with laughter.

That my views as to the function of the spleen
may be understood, I must repeat here what has
already been stated, viz., that it is probable that for
sustaining animal life it is necessary that the animal
spirits, i.e.^ nitro-aSrial particles, should traverse the
brain, or at all events the cerebellum, in continuous
series, and that that is the reason why on the suppres-
sion of the respiration or on the interruption even for
an instant of the motion of the heart, the higher
animals at once die.

If this is granted, it follows that the nitro-aerial
particles must be perpetually carried away again by
certain vessels ; and, mdeed, we may believe that the
nerves dedicated to the natural motions, and also
those belonging to the viscera, serve to carry away
the animal spirits from the cerebellum. But as for
natural functions, particularly for the digestion of
food, there is need now of more and now of less
afflux of nitro-aerial spirits ; while the nitro-aerial
particles pass through the cerebellum in a nearly
uniform flow : it is, hence, necessary that the super-
abundant nitro-aerial particles, those, namely, which
are not required for natural functions, should be con-
ducted elsewhere, and it is probable that the spleen is
formed in order that these superabundant nitro-aerial
particles should by means of it be properly mixed
with the mass of the blood. For these nitro-aerial
particles being discharged by the splenetic nerves
into the spleen are by its means, being diffused
through its parenchyma, most intimately mixed
with the mass of the blood : whence it comes about
that an effervescence sufficiently intense but yet not
too impetuous is excited by the nitro-aerial particles

On Muscular Motion and Animal Spirits 271

mixed abundantly but uniformly with the saline-
sulphureous particles of the blood ; so that the spleen
really seems to perform these three functions : —

1. That the nitro-aerial particles which pass in
continuous series through the brain, but are not
required for natural or animal functions, should be
carried into the mass of the blood and properly
mixed with it.

2. That the nitro-aerial particles may be brought
in suitable abundance and with a certain control to
the viscera devoted to the digestion of food. For
as these viscera are filled with food or empty, so they
have need of a greater or of a less afflux of fermentative
particles.

3. That the nitro-aerial particles in a condition of
motion and vigour should, when most intimately
mixed in the substance of the spleen with the saline-
sulphureous particles of the blood, excite in the mass
of the blood such an effervescence as is fitted to
bring its saline-sulphureous particles to a proper
volatility.

As to the former uses here assigned to the spleen,
the plexus and various communications among the
splenetic nerves and among those distributed to the
other viscera seem to confirm them. For by the
communications it is brought about that the nitro-
aerial particles are brought to the viscera serving
for the digestion of food, and for other natural
functions now in greater and now in less abundance
as there is need, and what of the nitro-aerial particles
is over is turned aside into the spleen.

And in this we may seek the reason why, when
the spleen is affected by scirrhus, or obstructed in
any other way, the patient suffers from eructation
and hypochondriac flatus : for inasmuch as the nitro-

272 Mayow

aerial particles cannot now, as at other times, pass
through the spleen on account of its obstruction,
they are carried into the stomach, the pancreas, and
the other viscera of digestion without any moderation
or control. But the digestion of the food and chyme
is carried on too quickly by these particles mixed in
too great abundance with the chyme in the stomach
and other parts of the abdomen, and consequently
very impetuous and flatulent fermentation^ must
arise.

Further, as the nitro-aerial spirits cannot be dis-
charged into the obstructed spleen, it is probable that
they to some extent regurgitate towards the brain
and the cerebellum, whence it comes to pass that the
motion of the animal spirits will be perverted, and
consequently the brain and the animal economy
perturbed, as often happens in hypochondriac
affections ; although this may also be produced by
another cause, as will be set forth below.

And besides, this also points in the same way that,
namely, the spleen in infants is florid and scarlet,
although later it acquires a black-blue colour. For
that difference of colour seems to come from this,
that in infants the nitro-aerial particles come only
sparingly to the spleen, so that as yet scarcely any
fermentation is excited in it, as will be more fully
stated presently. But the reason why the spleen
does not perform its function in infants seems to be
this. The foetus in the uterus, as also for some time
after birth, has hardly any, at all events no violent
exercise, and the heart and the organs of respiration
do not as yet need to work at all hard : for these
natural functions are specially increased in violent
motion of the body, as has been shown above. Hence
the nitro-aerial particles are transmitted through the

Oil Muscular Motion and Animal Spirits 2^2)

cerebellum and the nerves arising from it only gently
and with a constantly even flow ; particularly in the
uterus, where, namely, the infant does not yet exercise
the respiratory organs. Whence it comes that the
spleen cannot be of any use, in so far, that is to
say, as the nitro-aerial particles traversing the cere-
bellum in a slender stream are almost all required
for the natural functions : but when the animal has
grown up and exercised itself in violent labours, it is
necessary that these nitro-aerial particles should be
transmitted through the cerebellum in greater
abundance, so that the nitro-aerial spirits may now
make for themselves sufficiently open channels in the
cerebellum, and that the structure of the brain may
become more compact and firm, and so the nitro-
aerial particles in the future may more easily and in
fuller rush pass through the brain and the nerves
arising from it. But when these are not all required
for carrying on in the usual way the natural functions,
it is most necessary that the superabundance of nitro-
aerial particles should be discharged into the mass of
the blood and most intimately mixed with it by
means of some organ, such as the spleen.

I add, besides, that while the foetus is in the uterus,
the viscera devoted to the digestion of food have
either nothing to do, or at all events act very remissly.
Whence it happens that the nitro-aerial spirits do
not go at all to these viscera, or at all events only in
very small amount ; and there is thus no need that
any part of them should be diverted to the spleen.
Further, as the infant immediately after birth takes
food continuously, or at all events at frequently
repeated times, so that its stomach is to some extent
filled with food, and consequently the nitro-aerial
spirits ought to come to the viscera devoted to

S

2 74 Mayow

digestion in an always even flow and without any
regulation, yet when the animal has come to the
limit of its growth it takes food at fixed periods,
and its stomach is sometimes filled with food and
sometimes nearly empty : and hence it is necessary
that the nitro-aerial particles should be carried now
in larger now in smaller abundance to the viscera of
digestion. But that the afflux of nitro-aerial spirits
to the viscera should take place under control, it is
necessary that there should be some organ in the
parenchyma of which the excess of nitro-aerial spirits
may be deposited, as has been shown above.

As the primary function of the spleen has no place
in infants, so neither is it necessary that its other
office, that is, the more intense effervescence of the
blood (which we have said takes place in the spleen),
should be exercised in infants. For it is probable
that the said fermentation excited in the spleen has
for its chief eff"ect the bringing of the saline-
sulphureous particles of the blood to a proper
volatility for motive and procreative functions, and
these functions do not well suit a tender age.

We gather from what follows that an effervescence
of that sort is excited in the parenchyma of the
spleen by the nitro-aerial particles brought along the
nerves and mixed with the saline-sulphureous particles
of the blood.

For it has been made out by observation that if the
spleen is obstructed by scirrhus, the mass of the blood
lacks its proper fermentation and becomes crude and
vapid, so that dropsy and chlorosis often result.
But I confess I do not know whence that fermenta-
tion excited in the spleen should arise, unless from
nitro-aerial particles along with the saline-sulphureous
particles of the blood ; for I cannot agree with those

On Muscular Motion and Animal Spirits 275

who hold that the thicker and more fixed part of the
blood is detained in the substance of the spleen, and
that it, by being long kept, acquires a fermentative
character ; for if particles of blood anywhere cease
from movement and stagnate, these particles will
prevent those immediately following from continuing
their motion, and thus, the circulation of the blood
being in that part interrupted, swelling and inflamma-
tion will necessarily result. Moreover, the numerous
branches of nerves disseminated in the spleen seem
to serve no other purpose but that of conveying
fermentative particles.

Besides, as, when the fermentation in the spleen is
too remissly performed the blood becomes too crude,
so on the other hand if it is increased beyond a right
extent the mass of the blood acquires a somewhat
dried and atrabilious character. Indeed, as in fire
the nitro-aerial particles effervescing most intensely
with the sulphureous particles burn them up in an
instant and turn them into smoke, as we elsewhere
show, so also if in the parenchyma of the spleen
the nitro-aerial and the saline-sulphureous particles
work together too much, it comes to pass that these
particles become to some small extent dried up and
sooty, and from them, fixed in the substance of the
spleen, its dark purple colour seems to come. But
that atrabilious diathesis of the blood may arise from
a twofold cause.

I. If the saline-sulphureous particles of the blood
are detained in the spleen by reason of its paren-
chyma being obstructed ; for thus they, by effervescing
too long with the nitro-aerial particles, become
torrefied and dried. Indeed the mass of the spleen
seems to be composed of two kinds of vessels ; of which
one, consisting of nervous fibres, is destined for the

276 Mayow

distribution of nitro-aerial spirits, and the other for
the diffusion of the blood, and besides for the reception
of nitro-aerial particles. If the obstruction takes
place in the former, the mass of the blood will lack
its due ferment, the influx of fermentative spirits being
shut off from the spleen ; but if the latter are ob-
structed, the saline-sulphureous particles of the blood
detained too long in the parenchyma of the spleen
and too much fermented, will acquire an acid and
dried up, or what is the same thing, an atrabilous
character.

2. If the substance of the spleen is corroded by an
ulcer, or in any other way broken, the nitro-aerial
particles will not now as at other times be mixed in
its parenchyma intimately and uniformly with the
mass of the blood, but in a too crowded and confused
way, whence a too intense effervescence is set up, on
account of which the saline-sulphureous particles of
the blood become much dried up and sooty.

From what has been said, it is not difficult to
understand how it is that an animal can live when
deprived of so notable an organ as the spleen ; for
although the offices here assigned to the spleen
conduce in no small degree to the correct carrying on
of the animal economy and to perfect health, still
they are not so necessary but that life can be kept up
in a so-so way without them.

We may here note, by the way, that the parts of
all sorts of animals contain an ample quantity of
volatile salt, but scarcely any fixed salt, as is shown
by their distillation and combustion ; and yet many
animals live on vegetables only, and in these there is
little or no volatile salt to be found, but much fixed or
rather nitrous salt : so that it would plainly seem
that the fixed or nitrous salts of the food are trans-

On Muscular Motion and Animal Spirits 277

formed inside the bodies of animals — in that chemical
workshop of nature — into volatile salts. And the
same thing is indicated by the fact that if plants
which contain no volatile salt are allowed so far to
putrefy until they have been converted into worms,
then at last volatile salt can be obtained in abundance
from them by distillation.

As to the mode in which the fixed salts of the
food are volatilised, it is probable that the various
digestions and fermentations taking place in the
bodies of animals contribute in no small degree to
the volatilisation of the salts : indeed we may hold
that the spleen is the chief workshop in which
the nitrous salts of the food are worked up into
volatile salts. For, indeed, it is to be observed that
when vegetables are burned, their nitrous salts are
volatilised ; and they flying off along with sulphureous
particles, somewhat dried up, constitute the soot.
And soot abounds in volatile salt, although the
vegetables which, when burned, yield it, before their
deflagration, contained only fixed or nitrous salt.
And, as when nitre and sulphur are mixed together
and burned, as in gunpowder, it is probable that the
fixed salt, of which nitre in part consists, is volatilised
during the deflagration and flies off" in the vapours ;
for otherwise the fixed salt of the nitre would remain
after its combustion, for in the deflagration of nitre,
the nitro-aerial particles which it contains, set in very
swift motion by means of the ignited sulphureous
particles, most finely break up the saline particles
with which they were previously firmly combined,
and, as is probable, makes them volatile.

But if indeed the exceedingly impetuous and igneous
effervescence of the nitro-aerial and sulphureous
particles suffices to volatilise in an instant the fixed

278 Mayow

salts of vegetables, why should we not suppose that
that very intense working of nitro-aerial and
sulphureous particles excited in the spleen should
suffice to volatilise the fixed, or rather the nitrous,
salts of the chyle ? It tends in this direction also
that the saline-sulphureous particles in the spleen
become somewhat burnt and sooty, as we have
indicated above. We might here also show that
fermentations of all kinds excited in the bodies of
animals come from the working of nitro-aerial and
saline-sulphureous particles, if this were not foreign
to our present subject.

OF THE DISEA SES WHICH HA VE TO DO WITH
AmMAL SPIRITS

From the hypothesis as to the nature of animal
spirits stated above, we can at once say in what the
animal economy consists, and also can give an explana-
tion of many diseases which have to do with the
motive function.

For properly keeping up the animal life, it is first
of all necessary that the lungs should be in a healthy
condition, so that the nitro-aerial particles may be
transmitted in sufficient abundance into the mass of
the blood and intimately mixed with its sulphureous
particles. Hence, if the lungs are corrupted or even
wasting and flaccid, the mass of the blood will not be
properly fermented, on account of the deficiency of
nitro-aerial particles : and so, as the motive particles
of both kinds would be deficient, there would follow
extreme lowering of the powers, and weakness, and
consumption of the body.

Further, in order that the animal function should
be properly carried on, it is necessary that the nitro-

0« Muscular Motion and Animal Spirits 279

aerial particles brought with the mass of the blood
should be transmitted into the brain and the nerves
arising in it. If the nitro-aerial particles are either
not carried in sufficient quantity to the brain, or are
unable to pass along the nerves on account of their
obstruction, the animal economy and the motive
function cannot but be disturbed. And from this
cause apoplexy, paralysis, and diseases of that kind
seem not rarely to originate, as has been stated
above.

As the nitro-aerial particles have to be sent to the
brain, so on the other hand the saline-sulphureous
particles have to be altogether excluded from it ;
for if they, either on account of their extreme tenuity,
or because the passages of the brain are too open,
or on account of too intense fermentation of the
blood, make their way into the brain, they excite the
nitre-aerial particles, ?>., the animal spirits, to in-
ordinate motions. Hence the animal economy is
much perturbed, as probably happens in intoxica-
tion, epilepsy, and other diseases of the kind : for
liquors full of volatile sulphur, such as spirit of wine
and the chemical oils of vegetables, when taken too
quickly, not infrequently produce the diseases
mentioned. An observation which I have made
m(jre than once points in the same direction. For
I have known persons subject to paroxysms of a
maniacal sort and also convulsions, whose sputum,
while they were suffering from such paroxysms,
burst into flame like oil, or rather in the manner of
gunpowder, when it was put into the fire : it is indeed
probable that in this case the saline-sulphureous
particles of the blood had been carried so far that
they burst into the recesses of the brain and there
excited the animal spirits to inordinate motions.

28o Mayow

As to melancholia and mania, it is probable that
the saline-sulphureous particles of the blood detained
in the parenchyma of the spleen and long effervescing
there with the nitro-aerial spirits acquire an atra-
bilious and malignant character ; and that, besides,
they become so subtle that they penetrate deep into
the brain and perturb the animal spirits. For it is
probable that diseases of this kind which concern the
brain arise not so much from a diseased condition of
the animal spirits as from their perturbed motion
or even from their deficiency ; for as the animal
spirits consist of an ethereal matter, they canno
be subject to any change, as we have indicated
above.

It is, besides, required for the establishment of
animal life and the mbtive function that the mass of
the blood should be impregnated with saline-
sulphureous particles duly perfected, so that, namely,
the nitro-aerial particles mixed with them may excite
a proper effervescence in the mass of the blood.
For it is necessary for the sustenance of animal life
that the saline-sulphureous particles of the blood
should, by continuous fermentation of the blood, be
brought to a proper volatility; so that they being
separated from the blood by means of the muscular
flesh, may be transmitted into the motor parts, as I
have endeavoured to show above. But if, indeed, the
saline-sulphureous particles are not properly exalted
by reason of a too slight fermentation of the blood,
or are not promptly enough separated from the mass
of the blood on account of a diseased condition of
the muscular flesh, the motive function can scarcely
be set up. And so it is probable that the spontaneous
lassitude and incapacity for motion which accompany
scorbutus and the icteric disease proceed from this

On Muscular Motion and Animal Spirits 281

cause ; for these symptoms seem in the said diseases
to come not so much from a deficiency of animal
spirits as from a disorder of the blood and of the
muscular flesh.

We may note by the way, that the slighter
convulsions, like those tvvitchings of the tendons
which trouble many in continued fevers, may to some
extent arise from a diseased condition of the muscular
flesh, in so far as not only the saline-sulphureous
but also the nitro-aerial particles passing through the
now nearly wasted away parenchyma of the flesh,
are transmitted into the motor parts, and by their
mutual effervescence the often slight contractions of
the fibrils are, as is likely, produced.

From what has been said, the reason can be given
why bodily exercises are so useful in the icteric
disease and scorbutus, and also for warding off the
paroxyms of intermittent fevers. For in exercise the
nitro-aerial particles are sent in greater abundance
into the mass of the blood by the more intense
respiration, and the motion of the blood is much
promoted by the contraction of the muscles ; whence
it comes about that the fermentation of the blood
is increased and it is comminuted and worked up.
Further, the saline-sulphureous particles brought to
vigour are secreted from the blood and used up in
muscular contraction, and it is by their excess in the
mass of the blood that febrile heat is excited, as has
been elsewhere said.

282 Mayow

CHAPTER VI

OF THE MODE IN WHICH THE FIERI IS CONTRACT.
Also, OF THE MOTION OF CONTRACTING MUSCLES

So far as to the motive particles by which muscular
contraction is effected : it remains to enquire how the
muscles are contracted by them. I cannot, for reasons
given above, admit that muscles are contracted by the
inflation of the fibres, a view approved by some. I
further add that the fibrils, which in our opinion
primarily undergo contraction, seem to be solid
bodies ; so that they are quite incapable of being
inflated.

As to the contraction of the fibrils, as far as I can
make out from anatomical observation and from
mental conjecture, the fibrils in their contraction
seem to undergo contortion. Certainly this mode of
contraction of the fibrils, namely, by contortion, is
most in harmony with the constriction and hardness
of contracted muscles. Further, a contortion of the
fibrils is specially suitable for the very strong pull of
muscles which is sometimes exerted with quite
wonderful force. And to these things we further add,
that the motion of the nitro-aerial particles, by which
in our opinion muscular contraction is effected, is of
a sort fitted for twisting the fibrils, as, I think, will be
established by the following experiment.

Let a very fine music string be grasped by the
fingers of both hands at a short distance from each
other, and be held a such a height above a lighted
candle that the string may be sufficiently heated but
not burnt. When this is done we shall feel the
string contract with a distinct enough force as it is

071 Muscular Motto Ji and Animal Spirits 283

affected by the heat of the lamp ; but that con-
traction of the string is not produced in the common
way, but the string seems to undergo a spontaneous
movement, and to run together into itself in the
manner of fibrils — a very pleasant sight. But if the
contracted string be removed from the lamp it can
be drawn out to its former length with very little
effort. As to the cause from which the contraction
of the string proceeds, we may believe that the nitro-
aerial particles, bursting out of the flame of the lamp,
produce that contraction of the string ; for we have
elsewhere shown that igneous particles of any kind
(and it is by them that the said string is contracted)
are nothing else than nitro-aerial particles in a state
of motion. But the contraction of the string seems
to proceed from its being twisted by the nitro-aerial
particles : for if one end of the cord is left free, or if
it is held less firmly between the fingers and brought
towards the lamp, we shall see the cord rotated
pretty quickly. For as the nitro-aerial particles
bursting out of the lamp with the circumgyratory
motion proper to them act on the said cord, they
drive it round with their own motion and twist it.

And it is certainly probable that the contraction
of the fibrils is accomplished in a not very dissimilar
way : for the fibrils, in which the contraction primarily
takes place seem, in as far as the microscope can
help us, to be very like an extremely slender music
string. Besides, we suppose that the contraction of
the fibrils is caused by nitro-aerial particles set in
motion, and even pretty intensely warmed in the
motor parts. Wherefore, if a coarse and thick cord
undergoes contraction when touched by nitro-aerial
particles, how much more should the extremely
slender fibrils, fashioned with the highest skill, follow

284 Mayow

the motion of the nitro-aerial particles ? And it tells
in the same direction that a muscle, like the aforesaid
cord, cannot be brought again to its original length
without the exercise of some force. And this is the
reason why a cramp is wont to be produced in a
muscle when its antagonist is paralysed. For when
a muscle is once contracted, it will remain in that
state until it has been restored to its former length
by the pull of its antagonist.

From this hypothesis of ours it is not difficult to
understand how it is that when the motor parts have
been struck by lightning they are not unfrequently
convulsed, and remain tense, although the skin
surrounding the muscles is often uninjured. For I
have tried to show above that the nitro-aerial particles,
not only those in the brain but also those in the
motor parts, are sometimes as it were set on fire when
struck by lightning : nay, the nitro-aerial particles
thrown into an almost igneous motion, twist and
wrench the fibrils so violently that they cannot again
be drawn out, but will remain always tense ; just as it
would happen to the above-mentioned string if it
were brought too near the flame of the lamp.

OF THE MOTION OF CONTRACTING MUSCLES

Now that we have in this way considered how
muscular contraction is caused, it remains for us to
enquire shortly as to the motion of the muscles as
they contract, and also that of the parts attached to
them : but that this matter may be more clearly
understood, I shall premise the following.

In the first place, we lay it down that if any string
with both ends free contracts uniformly, both of its
ends will be drawn towards the centre.

On Muscular Motion and Animal Spirits 285

In the second place, if one end of the string to be
contracted were free but the other end fixed, that the
free end and also all parts of the string would in
contraction be drawn towards the fixed end ; as is
shown in Plate III., Fig. 4, which represents the string
so arranged and the same when contracted. For in
the said figure not only the free end of the string,
c, but also its middle point, a^ and so also all parts of
it, are drawn in the contraction of the string towards
the end, 3, which we suppose fixed. And similarly
we infer that if a greater weight be attached to the
one end and a smaller weight to the other, the
smaller weight will in the contraction of the string,
be drawn towards the greater as to a fixed end.

From what has been said, it will not be difficult to
understand the motion of the shortened muscle-s and
fibres. For if a fibre, fibril, or muscle, both of the
ends of which are free, undergoes contraction, it is
not to be doubted that both its ends will approach
the centre ; but if one of the ends is attached to an
immovable part, as is the case with the muscles which
serve for local motion, the contraction will be
altogether to the more fixed part ; and the movable
end, which in a muscle is called the termination, is
drawn in contraction towards the immovable end, or
what is the same thing, the head of the muscle. And
this also occurs in the contractions of the fibres or
fibrils. I am quite aware that the learned Dr Willis
has expressed a contrary opinion in his treatise
On Muscular Motion^ for that distinguished man
altogether denies that the fibres contract from the
termination towards the origin ; and indeed affirms
that when they are shortened, both of their ends are
drawn towards the middle. But with all respect to
such a man, when one end of a fibre is fixed to an

286 Mayow

immovable tendon, it seems to me necessary that the
more movable end of the contracted fibre, as also its
middle, should be moved towards the immovable end,
as is evident from the premises.

Therefore, as to the contraction of the fibres, of the
fibrils, and consequently of the muscles, I think we
must hold that they by no means, of their proper
nature, contract towards the origin rather than
towards the termination ; but do so only because
what we call the origin is inserted into an immovable
part. So that if the bone into which the termination
of the muscle is inserted should be more fixed than
that other one to which the origin is attached, then in
its contraction the muscle will be drawn towards its
termination. For example, let any immovable thing
be grasped by one hand, and then the flexor muscles
of the forearm be strongly contracted (which will
occur if we make an effort to draw the thing grasped
towards us), in this case, I say, as the thing grasped,
being immovable, cannot be moved to us, the said
muscles in their contraction will drag our arm and
our whole body which is attached to it towards the
thing grasped ; so that it will happen that these
muscles in their contraction will be drawn towards
their termination and not towards their origin ; inas-
much as the bone of the forearm in which the
terminations of the said muscles are inserted becomes,
on account of the immobility of the thing grasped,
the more fixed end : as is shown in Plate III., Fig. 3, in
which while the flexor muscles of the forearm, a^ c,
contract, they do not as in other cases bend the
forearm but the arm ; and in their contraction carry
3, c, towards the terminal tendon, c.

As to the motion of the sphincters, as also of
membraneous bodies, the motion of which ends in

On Muscular Motion and Animal Spirits 287

themselves, they are carried in their contraction
towards the centre of that space which they
surround.

CHAPTER VII

OF THE CONTRACTION OF THE DIAPHRAGM. ALSO,
OF THE PULSATION OF THE HEART, INCIDEN-
TALLY, OF THE PALPITATION OF THE HEART.
ALSO, OF THE MOTION OF ANIMALS WHEN THEY
RAISE THEMSEL VES ALOFT

In the last chapter we have spoken of the motion of
contracting muscles in general, and specially of the
tiexor muscles. Let us now further consider more
closely how the diaphragm moves when it contracts,
also in what manner the pulsation of the heart is
produced ; and, finally, how the extensor muscles, by
means of which jumping is effected, contract.

First, then, as to the contraction of the diaphragm,
although I have discoursed of it in my recently
published treatise On Respiration,^ still there are some
things which may be added here.

In the first place, then, I aflBrm as indubitable that
if a curved surface, the circumference of which is on
all sides fixed to an immovable part, undergoes
contraction, it will all round be carried towards the
immovable part, and the curved surface will ap-
proximate to a plane but will never go beyond the
plane ; as is shown in Plate III., Fig. 5, in which let
b, a, c be the curved surface and b and c its fixed
ends. As it contracts it will be brought towards the
plane 3, ^, c. So that the contracted surface b, d^ c,
that is to say its middle point d^ is nearer to the

288 Mayow

ends, b and c, than the middle point, a^ of the surface
not yet contracted, but that surface, however much
contracted, can never go beyond the plane, 3, c, as the
line, 3, e^ c, is the shortest between the ends, 3, c.

These things being granted, we assert that the
diaphragm in its contraction is moved towards a
plane ; in other words, when it contracts, it goes
towards the cavity of the abdomen, that is, outwards
and downwards. For it is known from anatomical
observation that the form of the diaphragm is curved,
and that its concave surface or sinus looks towards
the belly ; but now as any curved surface whatsoever
moves, in contracting, towards a plane, that is, towards
the region to which its concave surface looks, and as
the parts of the abdomen to which the concave
surface of the diaphragm looks are relatively to it,
inferior and exterior, it necessarily follows that when
the diaphragm, in its contraction, moves towards
them, in its contracted state it goes downwards and
outwards. And besides, this can be seen in vivi-
sections by simple inspection. In this connection I
am much astonished that the eminent Dr Willis, in
his Answer to Dr Highmore^ has expressed the
opinion, " That the diaphragm in violent inspiration,
such as sometimes occurs in the case of dying
persons, descends beyond the plane and becomes very
convex towards the intestines." For this does not
seem very likely : for it is not " possible that such a
descent of the diaphragm should be caused by the
lungs taking a long inspiration," as the distinguished
author supposed, inasmuch as the inspiration and
the swelling of the lungs are caused by the descent
of the diaphragm and the dilatation of the chest.
But the lungs never cause the descent of the diaphragm,
but in all cases follow its motion, as we have else-

On Muscular Motion and Animal Spirits 289

where shown ; and the diaphragm, in contraction, is
brought towards a plane but never recedes from it,
as appears from what has been premised.

I admit that in wounds of the chest or of the
diaphragm itself, the diaphragm is sometimes convex
downwards, but this does not occur in inspiration nor
does it arise from the lungs taking a long breath ; it
happens only in the contraction of the chest and in
expiration. For, indeed, in the dilation of the chest
gaping from a wound it has suffered, the air rushes
partly through the trachea into the lungs, but partly
also, by reason of its own elastic force, makes its way
through the opening of the wound into the cavity of
the chest ; so that when in expiration the space of
the chest is suddenly diminished, the air contained in
the cavity between the lungs and the internal wall of
the chest, as it cannot at once escape through the
wound, compressed by the contraction of the chest,
pushes the diaphragm, which is in diastole and
relaxed, and pressing it downwards makes it convex,
as I have assured myself by inspection in vivisections.

It is to be further noted as to the diaphragm that
its fleshy fibres proceeding from its membranous
centre, go out into the surrounding parts, into which
it is inserted : whence it comes about that as some
fibres stretched out in one direction, some in the
opposite, contract with equal effort, the membrane
between them is held in equilibrium : yet meanwhile
the diaphragm as a whole is carried downwards and
outwards, just as if it had fibres stretched over the
whole of its length.

290 Mayow

OF THE PULSATION OF THE HEART

As to the contraction of the heart, the distmguished
Dr Lower has given such an accurate description of
its motion, as also of its structure, that it is scarcely
possible to add anything to it. That the heart is
really a muscle, and that the contraction of its fibres
diminishes the space of its ventricles and drives out
the blood, is quite indubitable. But here we come
across a by no means small difficulty : for seeing that
the heart is contracted and becomes smaller in its
systole, how is it that at that very time it strikes
the left side of the chest ? For it would seem that
in its contraction the heart should rather move in-
wards and further f^om the wall of the chest.

Hence some have supposed that it is not the heart
but the great artery, distended with blood, which
strikes the chest. But in fact the great artery, soon
after its origin, turns backwards towards the spine^
so that its pulsation could not be felt outside. Nor
can we say that the auricles of the heart in their
contraction strike the thorax, because they, just like
the heart, become smaller in their systole, and
besides, their deeper position is less suitable for
striking the chest.

And lastly, we cannot believe that the apex of the
heart impinges on and strikes the thorax, because of
its vibration and jump ; for I have found from
vivisections that the pulsation of the heart is produced
by its ventricles swelling up into a tumour : in fact, if
the thorax of a dog be quickly opened, and a finger,
or the hand, be placed on the left ventricle of the
heart, you will feel the ventricle swell up with a jump
and strongly strike the hand or the finger placed on

On Muscular Motion and Animal Spirits 291

it. Indeed, if the finger be held at some distance from
the left ventricle, when the heart contracts the side
of that ventricle will be briskly dashed against the
finger. And that this is really the case has already
been remarked by the eminent men, our own
Harvey and Lower.

Harvey held that this kind of pulsation of the
heart arises thus : that while the walls of the
ventricles contract as to length, they must increase in
thickness, just as when other muscles contract they
swell up, becoming broader. T admit that the walls of
the ventricles of the heart do in contraction become
somewhat thicker, but it is scarcely credible that they
swell up sufficiently to account for the pulsation
against the chest ; for it has been made out that
muscles do not in their contraction swell up so much
as is commonly believed.

I think, then, that we should hold as to the pulsation
of the heart, that the fibres of the heart, in their
contraction, draw its cone towards its base as to the
more fixed end ; whence it comes about that the
walls of the ventricles are carried outwards, the
pressure of the contained blood contributing to this.
To this it may at once be objected, with Harvey,
that a curved fibre in contracting becomes straighter
and is not distended in a circle, and so as the walls
of the ventricles of the heart are in a circular position
they will be carried inwards towards a straight line,
and not outwards. I reply, if both ends of the curved
fibre were fixed, it would, when shortened, be brought
towards a straight position ; but if one of the ends of
the fibre be movable, and even is in fact moved,
it can, in its contraction, be distended circularly : for,
in Plate III., Fig. 9, let ^, i, b, be a curved fibre, or the
internal wall of the left ventricle of the heart, and a^ e^

2 92 Mayow

the septum of the heart. Now, I say, inasmuch as in
the contraction of the wall, a^ 3, its one end, b^ that is
the cone of the heart, is carried towards c, because of
the simultaneous contraction of a^ e^ the septum of
the heart, that wall is, in its contraction, carried
outwards to d^ and forms the line a^ d^ c, which,
although shorter than the line, «, 2, b^ still rises as a
tumour at d. The distention of the wall is to no
small extent due to the impulse of the blood which,
strongly compressed by the contraction of the heart,
as it cannot all immediately be driven into the great
artery, gives a blow to the wall of the ventricle.

Should any one ask here how the blood contained
within the contracted ventricle, a^ d^ <;, is expelled
from it (for it is not to be supposed that in the systole
of the heart the ext^reme part of the heart moves
quite up to the base of the heart, but that some space
remains between them), T answer that it has not yet
been established that all the blood leaves the
ventricles each time that they contract. And at
any rate, if the ventricles of the heart were nearly
emptied of blood it would seem that what remains of
the blood could not be compressed by them with
force sufficient for the projection of the blood to the
furthest members of the body. If, however, all the
blood is expelled from the ventricles, we must suppose
that the walls of the ventricles continue their
contraction for some little time after that first rush
of the heart by which the pulsation is started. For
otherwise it seems impossible that all the blood
should be driven by the beat of the heart so
instantaneously into the great artery. And it tells
in favour of this, that in the section of animals, when
the dying heart is opened, the movement of contraction
is seen to be completed not at one stroke, but to

On Muscular Motion and Animal Spirits 293

begin in the septum and be gradually propagated in
the walls of the ventricles. No doubt, for first setting
the blood in motion there is need of a powerful con-
traction and jump of the whole heart ; while yet a
more gentle constriction of the ventricles may suffice
for keeping it going.

For the further expulsion of the blood from the
heart, its septum and ventricles contract not only
as to their length but also as to their breadth ; for the
fissures or little excavations with which the cavities
of the heart are hollowed out, have a position which
suits the heart when constricted from all sides, as the
eminent Lower has noticed. And it tells in favour
of this that the fibres of the heart are attached all
round to the orifice of the great artery ; whence it
comes that in their contraction they pull the sides of
that orifice in all directions and open a wide door for
the blood bursting out.

Nor should we omit to state that the long diameter
of the septum of the heart is not straight, but is
gibbous and convex on the right ; but in respect of
the left ventricle it is concave, or at least plane ; as
is shown in Plate III., Fig. 9. Now this form of the
septum conduces in no small degree to the propulsion
of the blood from the left ventricle to the remotest
parts of the body; for when the wall of the right
ventricle contracts, the blood thus compressed pushes
against the convex side of the septum, and the septum
meanwhile contracting by its own force, becomes
straighter, and still further narrows the space of the
left ventricle, as may be seen in Plate III., Fig. 9.
So that, in fact, the pressure of the contracting right
ventricle also contributes no little to the contrac-
tion of the left.

It is further to be noted that as the contracted

2 94 Mayow

septuQi is thus made more nearly plane, the heart as
a whole is carried to the left, as may be seen in the
figure. For when a motion has been once impressed
on the heart it continues for some time, in accordance
with the nature of projectiles ; and thus it comes
about that the heart brought to the left, strikes the
left side of the chest forcibly, though the greater
thickness of the wall of the left ventricle, its more
powerful pulse, not to mention its very shape, so
different from that of the right ventricle, contribute
in no small degree to this effect. And to these
things I may add that the spiral fibres in the walls of
the left ventricle are so arranged that, when they
contract, the heart is twisted by them, so that the
right ventricle is carried backwards towards the spine,
and the left somewhat forwards towards the chest, so
as to strike it.

From what has so far been said it follows, that if
the blood cannot escape with suflScient freedom from
the ventricles of the heart, on account of an obstruc-
tion of any sort whatever, either of the pulmonary
vessels or of the great artery, it cannot but be that,
as the heart violently contracts to expel as far as may
be the load of blood, the walls of the ventricles are
widely distended into a ball, and in consequence the
heart is dashed violently against the chest ; so that
the ribs are sometimes pushed out by its blows.
And it may be supposed that palpitation of the
heart, especially when long continued, proceeds from
this cause ; for although in this affection the pulsation
of the heart is very violent, still the pulse of the
arteries at the wrist is usually quite languid ; as has
been observed by others as well as by ourselves.
Besides, it points in this direction that in the bodies
of persons who have died of palpitation of the heart,

On Muscular Motion and Animal Spirits 295

the blood-vessels of the lungs, and also to some extent
the great artery, are sometimes found obstructed and
almost closed by the accretion of cartilage in their
interior, or by clots of blood, and the ventricles of
the heart, or at least one of them, inordinately
distended with grumous blood.

In confirmation of what has just been said, I may
here submit an observation made not long since by
the learned and ingenious Dr Thomas Millington,
who has kindly given me an account of it, as
follows.

A young man of good position, about twenty years
of age, of a delicate and slender habit of body,
suffered for some years from palpitation of the heart,
which was so violent that the ribs were forced out-
wards by the heart's impact, and a quite notable
tumour was formed on the left side of the chest ;
and if the hand were placed on it, the heart could be
felt violently dashed against the thorax, and one
could, so to speak, hold it in the hand. But yet the
pulse of the arteries in the wrist was very languid.
I can myself testify that this was the case with the
said patient.

Moreover this patient became breathless and suf-
fered from violent palpitation and faintness after any
brisker movement. And at last, after a long drive in
a carriage, he had a more violent attack, with frequent
swoons and coldness of the extremities, and died. On
opening the body the heart was found tumid, especially
its right ventricle, which was larger than usual and
turgid with coagulated blood ; indeed its muscular
wall was very thick and " strong. Further, the
pulmonary artery and vein were distended with
grumous blood, and that vein, where it opens into
the left ventricle of the heart, was nearly closed by

296 Mayow

cartilage adhering to its interior, so that blood could
scarcely enter the ventricle. Indeed, there can be no
doubt that the obstruction of the pulmonary vein
was the cause not only of the palpitation from which
the patient suffered, but also of the above-mentioned
phenomena. For as the blood could not, on account
of the obstruction, pass into the left ventricle of the
heart, the pulmonary blood-vessels and also the right
ventricle were necessarily distended with blood. So^
too, the heart, and especially that ventricle, was
forced to contract violently so as to propel the mass
of the blood as much as possible through the lungs
into the left ventricle of the heart. And this also
accounts for the great thickness and strength of the
right ventricle, since muscles accustomed to more
violent exercise increase more than others. But that
the heart should have been dashed against the left
side of the chest with such violence that its ribs were
bent outwards, although it was the right ventricle of
the heart only that was swollen like a tumour, is to
be explained by what has been said above ; for, indeed,
as the blood could not be all expelled from the right
ventricle because of the aforesaid obstruction, it,
compressed by the violent contraction of the muscular
wall of that ventricle, drove the septum of the heart
and so also the heart itself to the left side, as we have
shown above.

It is also to be noted that palpitation of the heart,
such, namely, as occurs suddenly and unexpectedly,
may come from this, that the blood, strongly
fermenting and set in violent motion, rushes too
quickly into the ventricles of the heart ; so that the
heart must needs contract with more than its usual
force to expel the greater quantity of blood. For it
must not be forgotten that the heart, like other

On Muscular Motion and Animal Spirits 297

muscles, is liable to convulsive movements, and its
palpitation seems sometimes to be referable to these.

As to the asthmatic paroxysm, to which the afore-
said patient was subject after any more violent
motion, that seems to have arisen thus, that the
blood which, on account of the contraction of the
muscles, reached the right ventricle of the heart in
a fuller stream, could not freely pass through the
lungs and make its way to the left ventricle of the
heart. But I would not have this so understood as
if I supposed that the blood detained in the lungs so
stuffed them up as to prevent the entrance of air
into them ; for, however the blood-vessels of the
lungs are distended with blood or any other liquid,
the lungs themselves do not swell up ; but all the
same they do enlarge when air is blown into them,
and quite promptly subside when the air is expelled,
as may be tested on the body of any animal by
passing blood or any other liquid into the pulmonary
vein after ligature of the pulmonary artery, and then
inflating the lungs by means of bellows attached to
the trachea. And in fact if the blood stagnate in the
pulmonary vessels, the patient is affected just as if
the respiration were suppressed ; for there are two
things specially effected by the respiration : —

First, that the mass of the blood should be led
through the lungs into the left ventricle of the heart
(yet that takes place not so much for the motion of
the lungs, as that the blood may ferment with the
nitro-aerial particles mixed with it by respiration,
and be protected from coagulation, as has been shown
above). Wherefore, if the blood for any reason
should stagnate in the lungs, as happened in the
case mentioned, the patient at once becomes breathless,
and suffocation is nearly produced.

298 Mayow

The other effect of respiration is that the nitro-
aerial particles should, by means of the blood, be
carried to the brain in quantity sufficient for the
renewal and completion of the animal spirits ; and
unless that takes place, a failure of the spirits and
swooning will soon follow on the suppression of the
other respiration— that of the brain.

HOW JUMPING IS PRODUCED

We shall add here as a corollary something as
to that motion by which animals lift themselves
altogether from the ground and jump. This motion
is produced, according to the view of the distinguished
Willis, not by the contraction of muscles, but rather
by some elastic force. For, indeed, that learned man
says in his Answer to Dr Highmore — " Tf there is no
attraction except to an immovable part, how can an
animal move its whole body and completely lift
itself from the ground : surely the motion of the
whole follows the motion of the individual motor
parts, wherefore if these can be drawn only one
towards another and not lift themselves wholly by
some elastic power, I confess that I do not understand
how and by what further artifices an animal is able
to lift itself as a whole and jump hither and thither."
But I really cannot conceive what the learned man
understands by an elastic force of the organs : there
is, however, no reason why we should seek refuge in
it, for the motion of animals raising themselves from
the ground can be produced quite conveniently by
the contraction of the extended muscles, as will be
made plain by what follows. For in Plate III., Fig. 6,
let a^ 3, be a stick, which we shall suppose to be

On Muscular Motion ajtd Animal Spirits 299

rotated about a^ as a centre ; I say that while it is
moving in a circle, all the parts of it, say c, 3, strive
as far as in them is to recede from the centres of the
circles which they describe, and tend to move in the
straight lines, c, e^ and ^, e : for a similar argument
holds here as in the case of a stone rotated in a sling,
which always strives to get out of the sling and to
begin a movement in a straight line, as has long ago
been noted by the acute Descartes. But now if we
suppose that while the stick is in rotation it be set
free from the centre, a^ when it has come to a
horizontal position, it will no longer move in a circle,
but ascend straight up. These things being premised,
let (in Plate III., Fig. 7), a^ e^ be the tibia, c, ;z, the
thigh-bone, e^ b^ e^ the muscles which extend the tibia ;
when the animal is in the attitude for jumping, the
thigh-bone, <:, ;z, by the contraction of these muscles
will be rotated about the protuberance of the tibia at
^, just as the aforesaid stick was rotated about the
centre. Whence it comes about that the thigh-bone
thus circumgyrated will strive to move up ; and
indeed if it has been driven round with sufficiently
brisk motion by these muscles, that effort will attain
its end, and the thigh-bone will carry the tibia aloft
with it. And the case is quite similar with the
muscles extending the foot, the tibia, the thigh, and
the back : when they contract strongly, the parts
into which they are inserted are driv^en in a circle
and carried upwards, as is seen in Plate III., Fig. 8,
which shows the muscles extending the foot, the
tibia, the thigh, and the back, with the bones into
which they are inserted. The flexor muscles of the
arm, the forearm, and the hand have been drawn in
the figure because these muscles contribute not a
little to the lifting of the body, in so far of course as

300 Mayow

they, when violently contracted, forcibly raise up the
parts annexed to them, as any one can feel for
himself when he jumps. But this is to be noted
here, that these bones along with the parts attached
to them are not carried straight up by the contraction
of the said muscles, but that the thighs are carried up
and forwards, while on the other hand the back is
carried up and backward, as is made clear in the
figure ; yet so that in the motion of animals moving
straight up, the force which carries some parts
forwards and that which carries other parts backwards,
being in equilibrium, mutually destroy one another,
while the other motion by which all the parts are
carried upwards is unimpaired ; but as the animals
jump forwards or jump backwards so must the force
by which some parts are directed forwards, or that by
which others are directed backwards, prevail.

But that this may be still more clearly made
apparent, I say the said extensor muscles raise the
animal aloft in the same way as anything is thrown
from the hand.

For as to the force impressed upon things projected^
it is not to be thought of as anything else than
motion alone : when a thing is once set in motion it
will continue in it until it is retarded by bodies in the
way, or by the gravity inherent in itself ; for, since
(as has been noted by the acute Descartes), if a thing
is at rest we do not believe that it will ever begin to
move unless it is impelled to do so by some cause,
so there is no reason why we should suppose that if
a thing is moving it should intermit its motion of its
own accord, and not as hindered by something else.
For as inanimate things obviously cannot dispose of
themselves, but are altogether subject to the disposi-
tion of others, they must continue in the state in

On Miiscidar Motion and Animal Spirits 301

which they are until their state is changed by some
external cause. As to the impetus with which a
stone from a sling or a ball from a gun is projected,
we can suppose it to be nothing else than the very
rapid motion in which the projectiles were when
they emerged from the sling or the gun. But to give
an instance of what has been said, let us suppose a
pendulum let go at any point of the circle, while it
descends to the lowest point of the circle it does not
remain there at rest but mounts up to almost the
same height on the opposite side of the circle. But
what is it that causes this ascent of the pendulum ?
For as to gravity, it is not its character to cause the
ascent but on the contrary the descent of things ;
and yet in this case the gravity of the pendulum is
the cause of its ascent ; in so far as the pendulum
when it has come to the lowest point of the circle
has acquired, on account of the continued impulse of
its own gravity, a so much accelerated motion that it
can carry itself up : for so much higher as is the
point from which the pendulum is let go, so much
higher does it ascend on the other side ; and that
happens only because the pendulum, let fall from a
higher point, acquires, at the lowest point of the
circle, a more rapid motion and thence also a greater
impressed force. Nor is the case otherwise when a
ball is discharged from a longer gun ; for so it gains
a much accelerated motion, and in consequence also
a very great impressed force. Obviously the ac-
celerated motion or the impressed force of a stone
descending from on high, and of a ball shot out of a
long gun, are increased for quite the same reason,
because, as the stone descends or the ball passes along
the gun, the impetus of gravity, or the impelling force,
is renewed every moment.

302 Mayow

But to bring what has been said to bear upon the
present matter, when an animal is bent, so as to be
in a suitable position for jumping (and we note that
to begin jumping it is quite necessary that the animal
should first bend itself), and then the extensor muscles
contract all at once with a sufficiently powerful
impulse, it comes to pass that all the parts of the
animal are carried upwards, as follows from what has
been said above : but in as far as all the parts of the
animal, and thus the animal itself, are, by the action
of the said muscles, set in motion upwards, these
muscles carry the animal on high for the same reason
as projectiles are moved in any direction ; inasmuch
as the impressed force of projectiles is nothing else
than motion determined in a particular direction in
which the thing has-been made to move by some
impelling cause. And so far as to muscular motion.

FIFTH TREATISE

ON RICKETS. TO WHICH IS AP-
PENDED A METHOD OF TREAT-
MENT. SECOND EDITION.

There has been only one, as far as I know, who has
written anything on the subject of rickets, namely,
the distinguished Dr Glisson ; and that may seem
strange, because as a rule disease scarcely rages so
much as the incurable passion of writing about it.
And the very accurate treatise on this disease pub-
lished a good while ago by Dr Glisson, and the
authority of such a man, would have deterred me
from writing, but that I knew that he would readily
forgive one who reverences the truth although he
may to some extent differ from him. Yet, as I hasten
with him to the same goal, it cannot but be that I shall
for a great part of the way tread in his footsteps :
wherefore I shall sometimes, with apologies to so
eminent a man, repeat some things he has said before,
as this cannot be avoided.

This disease made its appearance some forty years
ago in the western parts of England ; and since then
(as it is the way of diseases and other evils to spread
themselves) has infested infants' cradles through nearly

304 Mayow

the whole of England, though more rarely in the
northern parts.

It is, then, infants that specially suffer from this
disease ; it is pretty frequent among those from six
months to a year and a half old, most frequent
between the ages of a year and a half and two years
and a half, so that the chief time of attack comprises
the two years immediately following the age of six
months.

The diagnosis of this disease, as of others, depends
on a knowledge of the symptoms, which are the
following.

The proportion of parts is irregular, namely : the
head larger than normal, the face in better condition,
the intelligence very acute for the child's age, the
external parts (especially the muscles), slender and
thin, the skin lax and flaccid, the bones for the most
part bent, and round the joints prominent and nodose,
the spine also variously curved, the chest narrow, the
sternum indeed acuminated, the ends of the ribs
knobbed, the abdomen somewhat tumid and tense :
so far for what is to be seen externally.

Internally, the liver is seen to be above the normal
size, as are nearly all the parenchymata ; the stomach
and intestines present a greater mass than in health ;
the mesenteric glands are larger than normal, even if
they are not strumous : so far as to the abdomen.

In the thorax the lungs are observed to be in-
farcted and tumid, sometimes purulent and strumous,
and very often adherent to the pleura. The jugular
veins and the carotid arteries are sometimes found larger
than normal, but the brain is normal except in propor-
tion and size.

To these has to be added a weakening of nearly
all parts of the body, also a certain torpor, and

On Rickets 305

indisposition to work and exercise ; for the children
•can only play sitting, and can scarcely stand on their
feet ; and at last, as the disease advances, the weak
neck can hardly sustain the weight of the head.

Such and so many are the symptoms of this
disease ; we have next to consider what is the evil
which is the fruitful parent of this numerous brood.

And in the first place we assume that the cause of
this disease does not consist in the access of vitiated
blood from the heart ; for in this case the whole
mass of the blood would be corrupted, and as this is
indiscriminately distributed to all parts, the impure
blood would affect all parts equally ; but this never
happens in this disease. For the head, as also the
viscera, except that they are larger than usual, are
healthy ; indeed the very parenchymata, which chiefly
consist of affused blood, inasmuch as they closely
resemble those of healthy persons, testify that the
blood is sound : for it is absurd to assume some sort
of elective attraction in virtue of which the head and
the other healthy organs attract what is good in the
blood, but send away the bad blood to other parts :
for this attraction, if it existed, would be present
€qually in all parts, as there is the same congruence
with good blood and need of it in all parts ; and this
is what is supposed to produce motion of this sort.

Secondly, we assert that the origin of this affection
does not consist in a depraved constitution of the
parts themselves, as if parts suffering from intem-
perate cold and moisture were unfit to receive the
blood coming from the heart : for whence arises such
excessive moisture and coldness of some parts, when
all are similarly and equally irrigated by the spirits
of the warming blood ? Nor do I think coldness
innate in the parts, but in them over and above their

u

30 6 Mayow

nature ; nor is it to be believed that the parts them-
selves resist their own nutrition. For they take na
active part in nutrition, but only passively receive the
nutriment brought to them : so that I do not believe
in any unfitness in the parts, which would lead to their
being less nourished, but only that there are obstruc-
tions which prevent their reception of the aliment :
wherefore the cause of this disease cannot be in the
constitution of the parts themselves ; nor are we to
look on the moisture as the cause of this disease, but
rather as its consequence.

When, then, parts do indeed grow cold and are not
nourished, although saturated with quite suitable
blood, we must certainly conclude that something
besides blood alone is required for warmth and nutri-
tion. And whatever^ this may be, it must necessarily
be conveyed by some sort of vessels. The arteries
bring the blood, the veins carry it back ; and the
nerves alone remain as possible carriers of the nutri-
tive juice, or, at all events, spirits. And lest any
one should doubt that the nerves carry something
required for nutrition, I shall mention an experiment
known to every one, namely, that if the nerve serving
any part whatever be divided, not only does sensation
in that part cease, but also nutrition so that the said
part withers up.

But indeed this nervous juice does not alone per-
form the whole function of nutrition. For besides
it, the blood diffused by the arteries has no small
share in nutrition. For it is the case that the
nervous juice when mixed with the blood produces
a certain effervescence and heat, and thus suitable
material is precipitated for the nourishment of the
parts : and so the blood in this disease, although in
itself laudable enough, yet lacking the necessary

On Rickets 307

ferment on account of the defect of this nervous
influx, is not able either to excite the required heat
in the parts or to perform the function of nutrition.

We need not, then, hesitate to assert that the
disease of rickets arises from an unequal distribution
of the nervous juice, from the defect of which, or
from its superabundance, some parts, defrauded of
nutriment, shrink, others, saturated more than
enough, grow to an excessive size.

The error causing this inequality does npt lie with
the flow from the brain, for if this fountain were
vitiated no suitable nutriment could come to any
part : for indeed the head and the other parts which
are supplied by the cerebral nerves enjoy sufficiently
good nutriment, though more than enough of it.
And yet those parts which have nerves originating
in the spinal marrow, being defrauded of nutritive
juice, are emaciated. This is a clear proof that a
sufficient supply of vital spirits is elaborated in the
brain as in the public workshop of the whole body ;
but that the spinal marrow, as the highway leading
from that emporium, is overlaid and obstructed by
thick and glutinous humours, so that the access of
nervous nutriment is cut off: whence it comes that
the nerves arising from the spinal marrow lacking
that nutritious juice, bring no supply of it to the
languishing parts to which they are distributed.
Thus these parts suffer from atrophy and extreme
leanness. And it is thus reasonable that we should
assign this as the cause of the disease ; specially as
all the symptoms proper to this disease can be clearly
and easily shown to be derivable from this source,
as shall be made plain in what follows.

I. It happens in this disease that the head increases
in size beyond the just proportion ; and this is what

3o8 Mayow

we should expect from our supposition, for the nutri-
tious juice of the brain, which in other cases is in
great part sent into the spinal marrow, here, as that
road is closed, is all dispensed by the cerebral nerves.
Hence, as the head is supplied by these nerves turgid
with nutritious juice, it obtains a more liberal supply
of nutriment and necessarily grows in a more than
proportional degree. Hence, also, the face is better
conditioned and the mind more acute than accords
with the •age, for as the exhaustion of the spirits
makes us torpid and languid, so their abundance, con-
gested in the brain, makes us wise and ingenious.

2. The abdominal viscera are wont for the most
part to exceed the normal proportion ; and here the
same argument holds as in the case of the head, for
it has been certainly made out that all those plexuses
of nerves devoted to the service of the lower part
of the abdomen are for the most part derivatives of
the vagus and of the intercostal nerves, which have
their origin from the brain ; so that we need not
wonder if these viscera grow largely, enjoying as
they do a fuller nourishment brought by the said
nerves. For although the nerves of an intercostal
pair receive branches from the spinal marrow, which
can bring no nutritious juice, still that defect is
abundantly compensated by the fuller supply from
the brain. As to the liver and the other parenchymata,
which seem to consist mainly of affused blood, per-
haps the nervous juice is not so necessary for their
nutrition. But as the muscles of the abdomen which
cover these organs derive their nerves from the spinal
marrow, and as they cannot bring any nutriment at
all from that dried- up fountain, it follows that the
viscera within swelling up, press with their mass
against these muscles and make them tense, as the

On Rickets 309

muscles do not grow in the same proportion as the
viscera.

3. Further, the mesentery is aflfected with enlarged
glands and strumous tumours. That the cause of
this symptom may be better understood, I shall
shortly explain the origin of glands. The nervous
juice when mixed with blood in due fermentation,
passes into nutritive and fleshy substance ; but if
the nerve, replete and turgid, pours out its juice,
which is very like white of Qgg^ into the interstices
of the flesh, the matter so poured out does not now
produce flesh, for want of the blood required for this,
but is coagulated into a glandular body very like
itself, as is shown by observation. For when I have
been about to make some experiment on a dog, I
have wounded a nerve : on this occurring, the dog
is painfully racked with convulsions : on dissection
after about three months, I found a pretty large
glandular concretion at the place where the wound
had been inflicted, and this seemed to have its origin
from the nervous juice escaping from the puncture
of the nerve. This being assumed, we see that when
the nervous juice is transferred from the replete
brain to the abdomen, by the before-mentioned vagus
and intercostal nerves, in such quantity that it cannot
be transformed into the substance of the viscera, that
juice is deposited in the interstices of the membranes,
of which there are many, and there gives rise to
numerous strumous swellings. And not in the
abdomen only, but wherever there are nerves arising
from the brain and turgid with that juice, there
strumous tumours may be seen : but these disappear
soon after the disease is cured ; for the nervous juice
which was poured out in such abundance from the
brain, by the nerves thence arising, and produced the

31 o Mayow

strumous swellings, is now for the most part diverted
into the spinal marrow, so that the strumse deprived
of nutriment, soon dry up.

4. The bones are always more or less bent in this
disease, particularly the bones of the leg and of the fore-
arm. The joints also are often inclined outwards ; the
extremities of the ribs, where they join with the carti-
lages of the sternum, are nodose ; the bones of the
joints are protuberant ; also the whole spine is bent
variously, here outward, here inward. I do not think
that this curvature of the bones is owing to their flexi-
bility, because the children afflicted with this disease
have rather larger and firmer bones than others, as will
later be shown at some length ; yet as this curvature of
the bones is very notable, I may be allowed to discuss it
somewhat more fully, ^and I shall first give the learned
Dr Glisson's opinion, and then shortly state my own.

Dr Glisson says : '' Let us compare the bones which
are apt to be curved to a pillar ; and indeed we
may do so quite properly, for if they are erect, they
correspond to a sort of pillar, and thence we deduce
a demonstration explanatory of this circumstance :
let, then, ^, h^ c (Plate IV., Fig, i) be a pillar com-
posed of three stones placed one on the top of the
other ; we shall suppose it such that every side is
perpendicular and of the same height ; if, then, we
insert a wedge on the right side between the stones
a and Z>, along the line /, ^, the head of the pillar,
that is, the highest stone, will be inclined towards
d^ and make an angle at d^ and the height of
the pillar will be greater on the right side than on
the left, as is shown in Plate IV., Fig. 2. Similarly,
if you push in another wedge along the line g^ <?,
between the stones h and c^ the pillar will be still
further inclined, and there will be an angle at e. The

On Rickets 311

pillar will therefore be inclined to the left, as is seen
in the same figure. But if the pillar is made of
many stones, and a wedge is inserted, as described,
between every pair of them, the stones will not have
the form of a pillar but of a portion of an arc, as may
be seen in Fig. 3.

'' To accommodate this to the present question, if the
said bones are more fully nourished on one side and
therefore grow more on that side than on the
opposite, it must necessarily follow that they will on
that very account curve, for the fuller nutrition of
that side brings about the curvature of the bone in
the same way as the wedge driven in brings about
the curvature of the pillar, except that while a wedge
is driven in at certain points only of the side of the
pillar, the fuller nutrition affects the side of the bone
nearly equally along its whole length, and it is on
account of this uniform nutrition that the inclination
of the bone produces an exact segment of a circle
without any angles."

According to this hypothesis, viz., that one side
is more fully nourished, the learned author by his
ingenious comment demonstrates the curvature of the
bones. But with all respect for such a man we may
ask, whence comes it that one side should have that
fuller nutrition when the blood by which the bones
are nourished is in this disease, no less than in healthy
persons, equally distributed ? And if there were any
such inequality, a fuller supply of aliment might be
supposed in the posterior side of the tibia, as that is
less exposed to cold, and so softer ; and thus the
posterior would be the elongated and convex side of
the curved tibia, and the anterior the concave ; but
the opposite is the case, for in this disease the tibia
is prominent in front.

312 Alayow

And further, from the very form of the curved
bones, we may gather that they grow equally on
both sides: for the bones have the form shown in
Fig. 4, which represents the tibia, where the concave
side, a^ is as long as the convex, b ; for if it were
otherwise, and the tibia had the form shown in Fig,
5, the thigh-bone, b, could not be supported on it with-
out manifest obliquity of the body, as may be seen
from the figure.

We must, therefore, look for some other cause of
this curvature ; and to see our way more clearly, the
following points should be noted : —

1st. We assert that in this disease the bones are
not to be reckoned among the parts affected in
respect to nutrition, for these are nourished and grow
no less than in healthy persons, as observation shows ;
for the blood alone suffices for their nutrition, and
there does not seem to be any need of the nervous
juice as in the nutrition of other parts ; for as bones
are not supposed to have any sensation of themselves,
they must be held to have little or nothing to do
with nerves.

2nd. We take it for granted that in this disease,
the nervous and muscular parts do not grow at all
because of the lack of the nervous juice necessary for
their nutrition.

These things being premised, let a in Plate IV.^
Fig. 6, be the tibia, b the muscles attached to that
bone behind and forming the calf. As, then, the tibia^
«, grows and lengthens, while at the same time it
is held, as by a string, by the muscles, which do not
grow in the same proportion, it follows necessarily
that that bone, strained by the shorter fibres of the
muscles, should be bent like a bow. I may illustrate
this hypothesis of mine by an example. If a string

On Rickets 313

be tied above and below to a young and growing
tree, yet so that the tree is not strained by the string,
as is shown in Plate IV., Fig, 7, every one will admit
that the said tree will be bent as it grows, as in Plate
IV., Fig. 8. And the mathematical proof of this is
obvious, for if any line is elongated while its extremi-
ties remain fixed, the line will cease to be a straight
line, and this is what happens to the bones in this
disease.

And this may be further confirmed by the fact that
the bent bones always have their concave side turned
towards the attached muscle, just as a bow and its
string, as may be seen in the case of the tibia, which
is prominent and convex in front, but concave on
the posterior side which looks towards the muscles ;
and the same is the case with the other bones — no
invalid argument that the bones are bent by the
muscles just as the bow by its string.

And this gives us the reason why quacks regularly
and successfully apply friction to the concave and
not to the convex side of the bones ; for by the more
plentiful supply of nutritious juice which such friction
calls forth, the muscle situated on the concave side
of the bone is nourished and grows, so that it is not
surprising that when the string is elongated the bone
strained and bent by it is also relaxed and becomes
straighter. And this is the reason why persons who
have recovered from this disease grow very much in
height ; for the bones not only grow as in other
persons, but in their return from curvature to straight-
ness are more elongated.

The spine is also variously bent, partly inwards,
partly outwards ; and this arises from the various
position of the muscles in different parts of the spine,
for the spine in its upper part is curved inwards by

314 Mayow

muscles attached to it externally, but in the lower
part it is curved outwards by the powerful Psoas
muscles attached internally, as is shown in Plate IV.,
Fig. 9, in which a, a is the spine, h the muscles
attached externally and bending the spine inwards in
its upper part, c the internal Psoas muscles bending
it outwards.

And I think that this cause of curvature is not
confined to this disease, but acts also in other cases ;
for if in tender age a muscle should be emaciated
because of any defect of nutrition, it must follow
that it will bend the bone to which it is attached.

The thigh-bone and the humerus, where the muscles
pull equally, being attached on all sides, are rarely
bent to any side, being held in equilibrium : while
yet, as they cannot extend in length they must do
so in thickness, and even sometimes develop nodes.

5. It occurs, besides, in this disease that the chest
is narrow and sharp : and this symptom can also
easily be illustrated on our hypothesis ; for the ribs
cannot expand their arches unless the intercostal
muscles are also increased, as can be seen in Plate
IV., Fig. ID, in which the portions of the ribs, ^, «, «,
a^ cannot be elongated unless the intercostal muscles
attached to them are similarly extended. But we
have assumed that the said muscles, inasmuch as
they are served by nerves derived from the spinal
marrow, cannot from defect of ahment be elongated,
so that the ribs cannot expand further and therefore
neither can the chest, but the ribs are nourished, and
yet, impeded by the said muscles, cannot grow in length ;
it follows, therefore, that they must develop nodes,
as they do. But this kind of growth does not corre-
spond to the abundance of nourishment, wherefore the
anterior extremities of the ribs are elongated into

On Rickets 315

points, because this is the only mode of growth left
free to them, as is shown in Fig. 11, in whxoha^a
are ribs, the extremities of which, ^, b^ grow outwards
in points, for they cannot be bent in, as this would
be still more opposed to their natural position.

To this kind of narrowness of the chest the muscles
of the abdomen also contribute in no small degree,
because, being, as we have said, extenuated and tense,
they thus draw down the lower ribs to which they
are attached, and so narrow the chest.

By quite a similar line of reasoning we could illus-
trate the disorders of the other bones ; for instance,
the bones of the articulation in the wrist and in the
ankle, which, on account of their shortness, cannot
be bent, form protuberant nodes. But what has been
said may suffice as to the curvature of the bones.

6. The above-mentioned narrowness of the chest
would lead us to expect that the lungs, not having
space for expansion, should be stuffed up with
grumous blood and swelled, as indeed they are, hence
they sometimes become purulent and the pleurse are
often adherent ; hence also the patients suffer from
asthma and difficulty of breathing.

7. As to the very great bodily weakness and in-
capacity for any movement in this disease, while the
emaciation of the muscles contributes something
to this symptom, yet this alone does not seem suffi-
cient, for the weakness is out of proportion to the
emaciation of the muscles, for the patients cannot
stand on their feet, nor, as the disease progresses,
sustain the weight of their head. So that we must
look for some other cause of such weakness, and this
can be nothing else than deficiency of animal spirits,
necessarily consequent on the above-mentioned
obstructions of the nerves. For animal spirits are

3i6 Mayow

absolutely required not only for nutrition but also
for motion.

And so, in fine, we have deduced the symptoms
of this disease from obstruction of the spinal marrow^
as its source.

And here it may be asked how it comes about that
older persons are never attacked by this disease^
seeing that they, as well as infants, suffer from obstruc-
tion of nerves, as in paralysis and other diseases of
that kind. I answer that although perhaps children
are chiefly liable to this disease, yet adults sometimes
suffer from the same disorder under another name.
Yet that the above-described symptoms for the most
part never appear in older patients, arises from a
difference not of disease but of age. For as the
great size of the head, the curvature of the bones,,
and some other of the symptoms are produced by the
abnormal increase in size of parts, it is altogether
impossible that adults, already at the limit of growth,.
i.e.^ unable to grow any more at all, should grow
abnormally : so that in adults suffering from this
disease the head does not, as in children, increase
beyond its proper size, because the head has already
attained the limit of growth which the very laws of
nature forbid it to exceed. But while the parts
cannot increase abnormally in adults, still the disease
does the one thing that in their case it can, by
emaciating them.

As to the prognosis, this disease is usually not
lethal in itself ; yet sometimes by the aggravation of
the symptoms it degenerates into Phthisis, Tabes,,
Hectic Fever, Dropsy of the Lungs or Ascites, and so
at last is fatal to the patient. But the prognosis can
be more easily established by the following rules : —

I. This disorder is most dangerous and often fatal

On Rickets 317

if it comes on before birth or immediately after
birth.

2. The sooner after birth this disease comes on, so
much the more dangerous is it.

3. The more the symptoms increase in severity,
viz., if the disproportion of parts and the emaciation
are extreme, so much the more difficult is the cure.

4. If this disorder has the above-named diseases
conjoined with it, it hardly ever terminates in re-
covery.

5. If the patients are not cured before the fifth
year, they will be invalids during their whole life.

6. Scabies or itching occurring in the course of
this disease contributes much to its cure.

7. We need have no doubt of the recovery of those
in whom the symptoms of the disease do not increase
but rather diminish.

Method of Treatment

Now that we have discussed the cause of this
disease and its prognosis, it remains for us to consider
its prevention and cure.

In so far, then, as the cause of this disorder consists
in obstruction of the spinal marrow, and weakness
of the nerves thence arising, the chief indications both
of prevention and cure are that the nerves be strength-
ened and the obstructions prevented or removed.
For this end, cathartic drugs, blood-letting, also
digestives, diuretics, diaphoretics, and specifics will
be called into use ; formulae for these and their mode
of use will be given below.

As to the cure of the disease, I think it should be
begun by catharsis ; which is more suitable in this
disorder, because phlegmatic humours are often col-
lected in great quantity in the lower part of the

3l8 Mayow

belly, and the abdominal viscera are frequently
affected with strumous tumours. Catharsis may be
set up by means of enemata, emetics, or mild pur-
gatives.

The Use of Enemaia, and some Examples

If the bowels are constipated, or the intestines
infested with wind and colic spasms, enemata may
often be employed. These are composed, not only
of solvent, but sometimes also of alterative and
strengthening drugs. I subjoin some formulae of
such :

^ Fol. Malv. m. j. Flor. Melilot. Chamcem. Sambuci ana
P.j. Sent. Ants. Fosnic. contus. ana l^ss. Cog. in lactis vaccin.
rec. s. q. Colatura '^iiij. v. vel vj. adde sacch. rubr. syr. Viol,
vel Rosat. ana §7. M. F.'- Enema Injic. tepide longe a pastu.

^ Rad. Alth. Contus. 3JJ. Fol. Malv. Parietar. ana in. ss.
Jhr. Chamcem. Sambuci ana P. j. sem. Carminat. '^ij. Cog.
in s. g. seri lactis cerevisiaii^ Colaturce '^v. vel vj. adde Elect.
Lenitivi^ vel Diacassice ^ss. Butyr. rec. Itvj. M. F. Enejna.
I?tjic. tepide.

Strengthening enemata may be compounded as
follows : —

^ Fimi egui non castrati recent, "^j.ss. flor. Rorismar.
Salv. ana P. j. baccar. Junip. 1,ij. sem. Anis. Fannie, ana
1)Ss. digerantur calide^ &^ clause cu7n seri lactis cerevis. s. q.
in Colaturce y^iij. v. vel vj. solve sacch. rubr. §/ Butyr. rec.
"^vj. M. F. Enejna, addi insuper potest., si visum est, ManncB
Calabr. 3^7- V^l

^ Millep. lotor. n. 20 vel 30, guibus contusis affunde seri
lactis ex vino albo parati %iiij. vel v. in expressione solve
sacch. rubri 37. Terebinth. Venet, in vitello ovi unius solut.
3/. vel ij. M. F. Enema tepide injiciendum.

The Use of Emetics^ and some Formiilce
If the stomach is loaded with vicious humours, and

On Rickets 319

these tend upwards, emetics should be exhibited ; yet
in preparing them, account must be taken of the
tender age. The vomits should consist rather of vitri-
olic salt and wine of squills than of antimonial drugs,
because it is not altogether safe to administer these
to infants, on account of the risk of convulsions ;
although sometimes even antimonial emetics may be
of use.

1^ Vini^ vel Oxymel. Scillit. ab '^s. ad 5/ quo sumpto,
post hora ss, serum lactis Cerevis. in magna copid superbi-
batur, dein digito, vel penna gutturi i7nmissis, vomitus
provocetur^ &^ aliquoties repetatur. Vel

^ Oxymel. Scillit. ab. "^ss. ad §/ si vomitus non succedat,
post horcE ss. sal vitrioli '^ss. vel gr. xv. in haustu seri lactis
cerevis. exhibeatur.

If the patient is strong enough, more powerful
emetics may be used. Such as :

^ Infus. Croci Metallor. per subsidentiam optime depuratce
d Zj. <^d Zij' P'^o ratione cetatis, viriumque : Oxymel Scillit.
Ziij- vel "ffSs. Aq. Jugland. simpl. vel Centaur. Minor, "^vj.
m.f. vomitor.

Some Examples of Cathartics

Some days after the vomit, or even if there has
been no vomiting, a mild purgation is to be set up
and repeated at intervals. As :

^ Syrup. Augustan, vel e dehor cum Rhabarb. d Ifuj. ad
§y. Crefnor. Tartar, gr. x. vel. xv. misce, capiat primo
mane., aut per se, aut in haustu seri lactis cerevisiati.

^ Mann. Calabr. ab ^ss. ad 5/ Tartari Vitriol, ct gr. v.
ad gr. X. misce, su??iatur mane in jusculo^ aut sero lactis
cerevisiati.

^ Rad. PolyPod. querc. Lapathi acut. ana 7)VJ. Cort. rad.
Sambuci^ Ebuli ana ^jj. rad. Osmundce regalis^ Filicis mar.
dehor, ana "^ss. herb. Agrimon. Hepat. Veronic. Ling.
Cervin. Aspienii ana 77t. ss. Coquant. in aq. fontan. lib. Hi.
ad terticE partis absumptionern. Liquor Coletur in matracium^

320 Mayow

cui imponantur fol. SenncB ^ij. Rhabarb. 3/ Epiihymt, San-
tali Citrin. ana "^tj. sem. Anis. Fcenic. ana oj. Sal. Absynth.
7)i.ss. f. infusio calida^ &^ claiisa per horas 1 2. ColaturcE
per subsidentiam depuralcB^ adde sacchari cBqiialem quanti-
iatejn, &^ sold sacchari dissolutione^ aut leni ebullitione f. s,
a. syrupus. Dosis Cochlear, j. ad iij. vel per se^ aut in
liquore appropriate.

Vel Infusioni superiori purganti adde CassicE, &= Tamar-
indor. cum parte infusionis ejusdem extract. Mannas ColatcB^
sacchar opt. ana 57. ss. Evaporent leni calore ad co?tsistentiam
electuarii. Dosis qu. micis Jugland. plus minus pro ratione
operationis.

^ Specier. Bier. pier, simpl. 3/ Rhabarb. opt. pulv. I^s.
Tartar. Vitriol. 37. Gic7n. Ammon. in ace to solut. gr. xv.
cum s. q. Elixir proprietat. Paracel. f. Mass. Pil, cujus
9 jj. ad 97. in exiguas pilulas forme tur, Or' exhibeatur hard
somni.

Bochetum ex Rhabarb.^ &' sant. citr. in aquis destillatis
idoneis fact, ex usu esse potest.

If the patient is affected with worms or strumous
swelHngs, or if there is a suspicion of Lues Venerea,
the following bolus may be given at intervals : —

!^ Mercur. dulc. a gr. 6. ad x. Resin. Jalap, vel Scammon.
gr. ij. ad iiij. ol. Junip. Chym. gutt. j. F. Pulv. qui cum
puipce pomi coct. aut co?tserv. Viol. 37- 2^ boluni redigatur.
Capiat primo mane^ vel

^ Mercur. dulc. gr. vj. ad x. Conserv. for. dehor. Z^s.
in. f: Bolus. Detur printo inane, superbibendo mox syrupi,
vel infusionis purgantis dosin idoneam .

Surgical Remedies
After purgation has been gently set up, if the
patient is of a sanguineous temperament, blood-letting
has its place. Our empirics are used to abstract
blood in small quantities by a scarification made in
the concha of the ear ; they perform this operation
rather with a blunt knife than with a sharp scalpel,

On Rickets 321

and repeat it two or three times at intervals of about
seven days. Although practical men make much of
this kind of scarification, I do not know whether
leeches would not do as well, or even better. For
I do not think that the leeches by their sucking
would cause any increased flow of blood to the head.
For whatever blood comes by their suction to the
part to which they are applied is removed by the
suction itself ; and as to the increased flow of blood
caused by the depletion of the blood-vessels, that
occurs in venesection as well.

Further, in this disorder issues are of special use,
particularly an issue between the first and second
cervical vertebrae, for in that position, close to the
origin of the disease, it has the greater efficacy.
And the usefulness of issues consists in this, that they
largely contribute to the evacuation of the super-
fluous serosity of the brain, and so to the diminution
of its abnormal size, and also to the drying up of the
excessive humidity of the spinal marrow, and conse-
quently to the strengthening of the nerves thence
arising. A seton can supply the place of an issue.

As to blisters, there can be no doubt that, placed
over the vertebrae of the neck or behind the ears,
they will bring relief ; but their action is suddenly
put forth, and their frequent use seems to be too
troublesome and painful to the children.

Further, cupping without scarification, applied
along the spine, seems to be of no small importance
for correcting the humid and frigid condition of the
spinal marrow and for removing the torpor of the
nerves. Indeed, I think cupping, even with slight
scarification, should sometimes be used close to the
upper cervical vertebrae.

322 Mayow

Alterative Specifics

Besides cathartics and surgical remedies, alterative
specifics may be employed, and to these diaphoretics
and diuretics should at times be added. I shall give
some examples of these.

The specific remedies which have been found
specially fit for combating this disorder are either
simple or composite. Among the simple the follow-
ing have proved themselves most useful : — Lignum
Guaiacum^ &^ ejus cortex. Sassafras, lign. Lentiscinum.
Ros7narin. Partes nodoscB lign. Abie tint. rad. Chinee. Sarsa-
paril. Tria Santalaj rad. Osmundce regalis^ seupotius spicce
rad. ejusde?n ; rad. Filicis maris ^ vel potius gemmce vix dum
e terra erumpentes. Rad. Graminisj Asparagi. Eryng. dehor.
Bar dan. Cort. rad. Capparumj Herbce Capillares., imprimis
Trichomanes J CeteracK. Ruta muraria; Ling. Cervin. He-
patica. Veronica mas. Agrimonia j Beccabung. Nasturt. aquat;
Fol. &" Flor. Salvice^ Rorismar. BetoniccB, Lajnice^ Tatnarisci.
Item Chalybis prcBpar. ut ejus sal, aut Vitriolum. Tartarum;
Castoreumj Flores sulp hurts j Vermes Terrestres ; Millepe-
des prcBparati, &^ similia.

These may be compounded as follows : —

1^ Spicar. rad. Osmund, regal, vel rad. Filic. mar. aut
Gejnmarum rad. ejusdem vix dum e terra erumpentium m.
j. Coquantur in lactis^ vel aq. font. lib. i. ad tertice partis
consumpt. Colatura saccharo edulcoretur^ &^ sumatur bis,
aut ter in die.

]^ Fol. Tece "^j. flor. salv. Beton. ana l^s. quibus vasi
idoneo impositis, superfundatur aqua., quce aliquandiu ferbue-
rit, lib. j. infundantur clause, &^ tepide per horam circiter
unam, colatura saccharo edulcoretur, &^ bibatur ut supra.

Bochetum, I Rad. Chin. Sarsapar, &^ Sassafras aq. fontan.
i?icoct. ex usu esse potest.

^ Spicar. rad. Osmund, regal, rad. Bardan. Gramin.
dehor, ana §7. Herb. Veronic. 7nar. Agrimon. ling. Cervin.
Hepat. Capil. vener. ana in. ss. ras. C. C. Ebor. ana fyss.

On Rickets 323

Passul. exacin. 37. coquantur in aq. fontan. lib. iiij. ad ter-
ti(B partis consmnp. adde vini alb. vel Rhenani lib. ss. &^
statim coletur in vas idoneum^ cui imponantiir^ Fol. Becca-
bung. Nastiirt. sumtnit. Abietis a?ta m. ss. Baccar. junip.
5«y^. F. inficsio tepida, &= clausa per horas circiter duas.
Colatura servetur vitris occlusis^ &^ edulcoreiur pro libitu.
Dos. ^ij. vel ^iij. horis medicis.

^ Lign. Lentiscin. Rosmarin. rad. Sarsaparil. Osmund,
regal, vel Filic. mar. ana ^iij. Herb. Agrimon. Capil. Ven.
Veronic. Ling. Cervin. Salv. Beton. ana. m. ij. summitat.
Abietis., Tamarisc. ana. 7ti. j. coquantur in cerevisice ?wti
lupulatcB cong. iiij. ad unius consumptionem^ colatura fer-
mentetur^ &^ in doliolum reponatur, i?i quo suspendatur
sacculus ex tela rant confectus^ &^ sequentibus repletus^ viz.
Milleped. in vino alb. lotor. &^ leviter contus. n. 200. Baccar.
Junip. "^ij. Nuc. Myrist. incis. n. ij. una cumfrustulo chalybis
ad sacculum submergendum. Si scorbuti suspicio sit, vasi
insuper imponi possunt, Fol. Beccabung. Nasturt. aquat.
ana m. ij. maneant per septimanas circiter duas, dein liquor
sumatur pro potu or dinar io.

^ Conserv. rad. dehor, Flor Beton. ana 3/ Conserv.
Anthos, Flor. Tamarisc. F laved. Limon. ana '^s. Myrobal.
condit. n. ij. Pulv. I Chelis Cancror. compos. 3/- Cremor.
Tartari, Flor. Sal. Annoniaci ana^ss. santali Citrin. 9/ cum
syrup, de Coral, s. q. f. Elect, capiat qu. nuc. Moschat. mane,
(Sr» hord quintd pom. superbibendo liquoris appropriati haus-
tulum.

^ Pulv. Milleped. pra;par. Zij- Nuc. Myrist. 7^s. flor. sal.
Annoniaci '^ij.f. Pulvis. Dos. gr. viij. adxv. in Apozemate,
Jusculo, aut liquore quovis convenienti.

Pulvis iste cum Balsami Capiv. q. s. in mas. Pil. redigi
potest, qucB in pilulas exiguas for7netur. Dos. circiter '^ss.

^ Rad. Ostnund. regal, vel Filic. ?nar. I^ss. rad. Pceon.
Mar. 3y. lign. sassafras, santali citrin. sem. Nasturt. aquat.
cina 9/ flavedinis Aurant. Condit, 7^j. f. Pulvis. Dos.
'^ss. ad 9/. ut supra. E pulvere prcescripto cum sacchari
albi in aq. Cerasor. nigr. solut. &^ ad Tabulat. cocti
septuplo, TabulcE formari possunt, quce singulce pendant J^.

324 Mayoiv

Capiat 1)SS, ad 3/. bis in die superbibendo liquorem appro-
priatum.

^ Rad. Ari, PcBon. Mar. Osmund, regal, vel Filic. mar.
afta ^iiij. fol. salv. Beton. Rorismar. Nasturt. aquat. Bec-
cabung. Veron. Mar. Hepat. summit. Abietis ana m. iij,
jugland. virid. lib. ss. Milleped. lotor. ^iij. Lwnbric. mundat.
lib. j. Castor, opt. 3/. Incis. &^ contus. affunde seri lactis ex
vino alb. parat. lib. vj. destillentur Communi destillatorio^
liquor totus misceatur. Dos. 37. ad "^ij. bis in die post dosin
medicamenti solidi.

Among the remedies which have been tried in this
^disease, the most celebrated is that devised by Boyle,
the name of it is Ens Veneris, It is composed
of sal armoniac and edulcorated colcothar, two or
three times sublimated together ; the dose is from
three to six grains taken in a suitable liquid at bed
time. I suppose that the efficiency of this drug
chiefly depends on the sal armoniac, as that is
specially suitable, on account of the extreme tenuity
of its parts, for removing the obstructions that pro-
duce this disease. And it is likely that the flowers
of sal armoniac will in this disorder be as eff'ectual,
or even more ; for while the sal armoniac is sub-
limed along with colcothar, a narcotic sulphur from
the colcothar, of an earthy or cupreous nature, sub-
limes with the sal armoniac. Now this sort of sulphur
does not seem very suitable for this disease.

An artificial salt, of an ammoniacal nature, and of
great virtue, can be prepared as follows : —

^ Sal. volatile C. C. Sanguinis^ aut Urines s. q. quibus
phialce oblongcB immissis, sp. sal. rectijicat, aut etiam suiph.
per Camp an. rectific. guttatim affundatur^ quousque ebullitio
non amplius excitabitur : sal hie resolutus^ per filtrum tra-
jiciatur^ &^ leni calore ad siccitatem salts abstrahatur. Dos.
gr, iij. ad vj. primo mane, aut hord somni in liquore appro-
priato.

On Rickets 325

Those medicines that consist of purely saline sal
volatile are of marked efficacy in this disease : among
such are to be reckoned the spirits of blood, of harts-
horn, of sal armoniac, and the like, especially these
spirits impregnated with amber or castoreum.

Elixir propriet. with tincture of salt of tartar, even
when prepared in the common way, is sometimes
used, not only because it is best for the digestion,
but also because it is suitable for killing worms and
for preventing corruption of the humours, and for
gently moving the bowels. The dose is six to ten
grains in two spoonfuls of a suitable liquid.

If the lungs are obstructed (as often is the case)
with viscid humours, and the mesentery affected with
strumous glands, balsam of sulphur may be exhibited.
Of this, three or four drops may be taken in a
suitable liquid, or in syrup.

Sometimes also the use of steel is appropriate, as
it is signally endowed with aperient virtue, and
not only assists the digestion but also confirms and
strengthens the tone of the viscera ; but it must be
used with caution, for steel is altogether to be avoided
in coughs, pleurisy, obstruction of the lungs, hectic
fever, and other diseases of that kind.

Diaphoretics are often added to the above-men-
tioned medicines, such as decoction of guaiacum and
others of that sort, which are to be taken in bed and
perspiration promoted as far as the strength will
allow.

We may here also refer to the use of the bath,
whether natural, such as the warm springs of Bath,
which have proved themselves of much use in this
disorder in provoking perspiration and in strengthen-
ing the nerves ; and indeed I have found by frequent
observation that the use of these warm springs con-

326 Mayow

tributes much to the reduction of the abdominal
swelling which is so marked a feature in this disease.
Artificial baths prepared with aqueous decoctions of
cephalic herbs and tartar or nitre may also be used.

Subsequent fomentation has been found valuable.
Let the patient be placed in a sufficiently large tub,
and be surrounded with tepid malt which has been
for a short time infused in boiHng water (as in the
process of making beer), and let him remain there
almost covered till perspiration is brought on.

Of the Symptoms

The symptoms supervening in this disease have
to be considered. Of these, the most common is
diarrhoea, for the cure of which mild cathartics,
such as infusion of rhubarb, tamarinds, and sandal-
wood, or a bolus compound of these, are specially
useful. Sometimes recourse must be had to astrin-
gents and bland opiates, of which formulae are to be
found here and there in books, but these are to be pre-
ceded by purgation and sometimes also by a vomit.

In addition, immoderate sweating is apt to occur in
this disorder. If this comes on in a febrile paroxysm
it may be critical, but it must not be rashly sup-
pressed. But if it be inordinate and exceeding what
might be expected from the cause, it is an indication
that the body is loaded with cacochymical humours,
and accordingly sweating of that sort is to be
corrected by mild purgation repeated at intervals ;
the purgation is to be brought about chiefly by
rhubarb ; sometimes a vomit may be joined with it,
nor should aperients and digestives be omitted.

Difficult dentition often occurs in this disease, and
not unfrequently brings on fever. When this is the
case, a gentle evacuation, best by clysters, should be

On Rickets 327

produced : although sometimes purgation and also
vomiting (which when gently brought on has proved
very serviceable) may be used. If the tooth is about
to pierce the gum^ nurses are used to rub it with a
stick of polished coral : instead of that, the root of
Althea or of Lapathus acutus may be used. It is even
sometimes right to make a way for the coming tooth
by means of an incision. Also epispastic plasters
behind the ears bring relief. Yet if pain and sleep-
lessness call for hypnotics, syrup of poppies may be
given in a dose of one to two drachms.

Besides internal medicines and surgical care, external
appliances will also be employed. Among these
are to be reckoned exercises of all kinds. If the
strength permits it, walking is much to be used.
But often the children play sitting, and are exercised
by being carried on the nurses' arms and by being
rocked in the cradle. For exercise promotes the flow
of blood and of animal spirits also to the muscular
parts, and thus heat is produced in these enfeebled
parts, as the mass of the blood is forced into swifter
motion by the contraction of the muscles, and is
impregnated with fermentative particles in the lungs
by the respiration made more intense by the exercise ;
while on the other hand the blood becomes thick
by constant repose and is made fitter for producing
obstructions.

Further, rubbings are of no small moment in curing
this disease : they may be made with warm woollen
cloths. The parts to be rubbed are the spine, which,
as has been shown above, is primarily at fault ; also
the muscular parts, yet with this caution, that there is
to be no rubbing where the bones are prominent, but
the concave parts of the bones are to be more liberally
rubbed : the reason for this has been given above.

328 Mayow

Of similar service is handling of the hypochondria,
pressing the viscera now upwards, now downwards,
and sometimes introducing the points of the fingers
below the false ribs ; for in this way care is taken
that the liver and the viscera do not suffer from any
unnatural adhesion to the peritoneum or elsewhere, as
not unfrequently happens in this disorder, on account
of the tenseness of the hypochondria.

Bandages are, besides, of service, placed on the legs
above the knee, and on the arms above the forearm,
but they should be loose and soft, so as not to inter-
fere with the growth of the part to which they are
applied ; indeed the usefulness of bandages consists
in this, that they tend to divert the flow of blood
from the head and to conduct it to the emaciated
parts.

Reference should also be made of the use of splints
applied to some parts, as also of leggings, which are
of no small use, not only for strengthening the parts,
but also for diminishing the curvature of the bones
and the flexure of the joints. In their use, care
should be taken that they press a little on the pro-
tuberant part of the bone but scarcely touch the
hollow.

For keeping the trunk of the body erect, stays
may be made, sewed in double cloth with numerous
pieces of whalebone placed between ; they are to be
so adapted to the child's body that the spine is held
erect and the prominent bones repressed.

Nor should we forget the artificial suspension of
the body by means of a pendulous instrument, so
formed of belts that the chest is embraced by it
below the armpits, that the head is surrounded by
another belt coming below the chin, and the hands
held by a pair of handles, so that the weight of the

On Rickets 329

body is sustained partly by the hands, partly by the
head, partly by the armpits of the child.

In conclusion, I add some remarks as to external
applications.

Fomentation with any kind of wine, or even with
common aqua vitae, does much to strengthen the
nervous parts, and may be applied to the weak parts
and especially to the spine : when that has been done,
these parts should be rubbed with oil or a suitable
ointment — as to these later. The following decoction
may be used instead of wine : —

^ Rad. Osmund, regal, aut Filic. Mar. ana '%iij. Fol.
Beton. Salv. Rorismar. majoran. Nasturt. aquat. ana m.j,
Jlor. Chamcemel. Melilot. Sambuci ana P. j. Baccar. Lauri,
Junip. ana ^s. Coq. in aq. font. s. q. ad lib. ij. adde vini
albij vel aqua vitce vulg. lib. j. Colatura usui servetur.

l^i Fol. Sambuci^ Lauri, Majoran. salv. Rorismarin. Beton.
summitat. Lavendulce ana in. ij. Baccar. junip. lauri ana
§y. incisa <Sr^ contusa vasi idoneo indantur cum butyri Maial.
vel butyr. recent, non saliti^ lib. iij. &^ aquce vitce lib.
ss. Coqu. lente ad aq. vitce consumpt. Expressioni adhuc
calidce adde ol. nuc. Myrist. per expressionem "^s. Balsam.
Peruv. 7)j- misce F. unguentmn^ loco butyri maialis substitui
potest medullce BovincE^ vel sevi Cervini, &^ 01. Lumbricor.
vel Vulpin. ana lib. i. ss.

Unguenta tepide coram igne luculento applicentur, &r>
calidd nianu ad siccitatem usque affricentur : quo autem
magis penetrent, liquoris appropriati aliquantulum iisdem
teinpore usus admisceatur.

If the abdomen be tense and tumid, the following
ointment may be applied : —

1^! 01. de Cappar. Absinth. Sambuc. ana 37. ung. de succis
aperit. vel unguent, supra prce script. 57. ss. Gum. Ammoniact
in aceto solut. '^s. F. linimentum : cui tempore usus porii-
uncula liquons sequentis admisceri potest.

^ Rad. Bryon. alb. 5/ fol. Absinth. Centaur. Salvice ana
m. j. Flor. Sambuci. Melilot.^ ana P. j. Baccar. Lauri^

33° Mayow

Ju7iiper. ana "J^ij. Coqu. 171 aq. font. lib. iij. ad dimidias.
adde vini Rhenani lib. ss. Colatura usui servetur.

While the ointments are being apphed to the
hypochondria, the viscera should be manipulated by
the nurse's hand, as directed above.

Plasters may also be used here. As :

^ Emplastr. de Melilof. compos, s. q. extendatur super
alutam &^ Hypochondris applicetur. Si tumor juxta
regionem Hepatis fuerit, adde Einplastri prcedicti 57. Santal.
Citr. pulv. 3/ ol. de Absinth. &^ cera; s. q. pro emplastro
conficiendo. Vel

^ Succ. Beccabung. Nasturt. aquat. Sambuci^ Absinth, ana
§y. Sued depurati lento calore ad consistentiam extracti re-
digantur, quibus adde Gum. Ammoniaci in vino solut^ &^
ad spissitudinem cocti ^ij. Terebinth. Venet. f^j. sant. Citrin.
pulv. Jyij. ol. de Cappar. &^ CercB s. q.f. Empl. applicand. ut
supra. <■

If the lungs are affected, the chest should be rubbed
with pectoral ointment or with ointment of dialthaea,
or with both mixed, to which at the time of applica-
tion there should be mixed a little expressed oil of
nutmeg. Or

^ GlycyrrhizcB rec. '^iij. Butyr. rec. non salit. lib. j. Con-
tundantur simul in mortario lapideo^ &^ macerentur calore
Balnei per horas 4, dein exprimanturj idemqj labor ter
iteretur cum pari quantitate novce Glycyrrhizce. Unguentum
s. a. depuraticm, usui servetur. Cui tempore usus unguent.
Pector. CBqu. quant, cum ol. nuc. Myrist. per express, parum
adjnisceatur.

As this disease arises from obstruction and weakness
of the spinal marrow, fomentations and strengthening
ointments such as have just been prescribed should
be applied to it, and to these a small quantity of
balsam of tolu may be mixed. Plasters are also of
use, such as nervine plaster or plaster of betony, or
also the following : —

On Rickets 331

^ Unguent, priinb prcescript. 527. Gum. Animon. in vino
solut. Pic. Burgund. ana '%ss. Mastich. Oliban. Carann. ana
3?/. Castor, "hss. Lumbricor. prcBpar. "^iss. Sal. Armoniac. T^ij.
Cerce. s. q. pro emplastro conjiciendo. A sufficient portion
of this is to be spread on leather, the shape of which
may be varied ; for as the upper or the lower parts
are weak the plaster is to be applied to the upper
or to the lower parts of the spine, sometimes, indeed,
to its whole length. So far of the method of treat-
ment.

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