Changes produced upon the Air by Respiration.

63

until the time of Boyle, that physiologists were fully sensible of the fact, that a perpetual supply of successive portions of fresh unrespired air is essential to life. Boyle discovered this fact in the course of his experiments with the newly invented machine, the air-pump; but as his ideas were principally directed to the investigation of the mechanical properties of the air, it was in this point of view that he almost exclusively viewed its action upon the lungs. Yet he was not altogether inattentive to the other changes which it experiences; he noticed the moisture which was exhaled along with it, and he further supposed that it carries off, what he stiles, recrementitious steams; but he does not give us any explanation of their nature. He also observed, that under certain circumstances, the air in which an animal had been confined for some time, was dimi nished in bulk; and this he accounts for by saying that it had lost its spring. Many of Boyle's contemporaries agreed with him in the opinion, that the blood parted with something to the air during its passage through the lungs; but there were, on the contrary, many eminent physiologists, and particularly among the chemists, who supposed that the blood acquired something from the air. This was

3 Boyle's Works, v. i. p. 99. et seq. and v. iii. p. 383.

• We have a curious statement by Boyle, Works, v. i. p. 107, of a person named Debrelle, who is said to have contrived a submarine vessel, and also discovered a kind of fluid, which supplied the navigators with what was necessary for their respiration, Boyle is well known to have been too much dis

5

the opinion of Sylvius, Baglivi,6. Borelli," Lower, and Willis, who imagined either that a portion of the whole mass of air, or that some particular part or element of it, entered the blood. Among these, the first in point both of genius and originality was Mayow, who investigated the nature of the change which the air experiences in respiration with peculiar felicity of experimental research and acuteness of reasoning. He announces the air of the atmosphere to be a compound body, and that it contained, as one of its constituents, a peculiar gaseous substance, which, from its supposed connexion with nitric acid, he termed nitro-aerial spirit. It was this nitro-aerial spirit which gave the air its power of supporting flame, and it was the same volatile spirit which imparted to the air its vital properties, and which the blood abstracted from it during its passage through the lungs. The hypothesis of Mayow seems to have attracted considerable notice at the time when it was proposed, yet it was shortly afterwards generally abandoned, and what is more remarkable, the experiments and discoveries of Mayow respecting the constitution of the atmosphere, which were extremely

posed to credulity; and we may venture to affirm, that the story, as he tells it, cannot be correct, yet it is scarcely probable that the whole was entirely without foundation.

6 Opera, p. 459, 0.

8 De Corde, p. 179. et seq. The great name of Newton

5 Praxis Med. lib. i. c. 21. 7 De Motu Anim. pars 2. p. 113. 9 Pharm. Ration. pars 2. p. 34. may be added to this list, as we find that he supposed there was an acid vapour in the air, which was absorbed by the lungs during respiration; Opera, a Horsley, t. iv. Optics, p. 245.

curious, and admirably calculated to advance our knowledge of natural philosophy, fell into neglect, and at length were almost totally forgotten.1

The total neglect into which the experiments of Mayow had fallen, during the greater part of the last century, must be regarded as a very singular occurrence in this history of science. He lived at a period when experimental research was becoming fashionable, and had been sanctioned by many illustrious examples; his experiments were simple in their contrivance, and many of them very decisive in their results, and there does not appear to have been any circumstance in the mode of their publication or the situation of the author, which should have prevented them from meeting with due regard from the public. He appears indeed to have been pretty fairly estimated by his contemporaries, as we find his works referred to both by the English and French physiologists, and generally spoken of with a due degree of applause. See Lubbock, in London Med. Journ. v. i. p. 220..2. After an attentive perusal of his works, I consider myself justified in pronouncing Mayow to have been a man of extraordinary genius, and one who, on many points, far outstript the science of, his age. Yet it must be confessed, on the other hand, that if, at one period, he was unjustly neglected, he has, at other times, been far too highly extolled. He saw the analogy of respiration to combustion, as well as the connexion which subsists between these processes and one of the constituents of the atmosphere, and he had also some conception of the modern doctrine of the formation of acids. But, I conceive, it would be no difficult task to prove, that on all these subjects, he had imperfect notions only, and that many of his ideas respecting the nitro-aerial spirit, as he terms it, are inapplicable to the modern oxygen, or to any other chemical principle. See note 30 of the Essay on Respiration.

In order to enable the reader to form a clear conception of the respective merits of our three countrymen, Boyle, Hooke, and Mayow, and of their claims to originality; I have subjoined the dates of some of their publications which give an VOL. II.

F

After the period of Mayow our knowledge respect ing the change which the air experiences by respira

account of the constitution of the atmosphere, and its effects on combustion, respiration, and other analogous processes. From these dates it may be fairly questioned, whether Mayow was always sufficiently candid in noticing the labours of his contemporaries. Boyle was born in 1627, and died in 1691; his principal works on the air were published between the years 1660 and 1675. Hooke was born in 1635, and died in 1702; he published the Micographia in 1665, and the "Lampas," in 1677. It is in the former of these works that he first detailed his ideas respecting combustion; Obs. 16, entitled "of Charcoal and Burnt Vegetables," p. 100. et seq. He commences the Lampas by referring to the Micrographia as containing "his hypothesis of fire and flame, which," he adds, "has so far obtained, that many authors have since made use of it and asserted it," p. 1. See also Waller's Life of Hooke prefixed to his posthumous works, and Ward's Lives of the Gresham Prof. p. 190. Mayow was born in 1645, published his tracts in 1674, and died in 1679. The substitution of the year 1697 for 1679, in Mr. Brande's Manual, as the date of Mayow's death, is, no doubt, an error of the press; compare p. 64 with p. 69. With regard to the estimate of Mayow's philosophical character, although, in many respects, I have the satisfaction of coinciding with Mr. Brande in the high commendation which he bestows upon it, p. 68. .79; yet I cannot but think that he, like Beddoes and Dr. Yeats, has over-rated his merits; at the same time, I admit, that in the contrivance and the execution of his experiments, he appears to have been more successful than any of his contemporaries. See Beddoes's "Chemical Experiments and Opinions," &c. and Yeats's "Observations," &c. Robison strongly advocates the merits of Hooke against those of Mayow; Black's Lectures, note 13. v. i. p. 535. . 8. and note 31. vol. i. p. 553. Fourcroy, I conceive, formed a more correct estimate of Mayow's merits; Encyc. Meth. art. Chim. t. iii. p. 390, and Ann. Chim. t. xxix. p. 42. et seq. Perhaps

Even Hales, who

tion was decidedly retrograde. devoted so much of his time and attention to the investigation of the properties of air generally, and to the subject of respiration in particular, appeared to have no distinct conception of any proper chemical effect being produced by this function, a circumstance which is the more remarkable, as it would appear that he was not unacquainted with Mayow's discovery. The result of Hales's experiments was that the air receives the addition of a quantity of aqueous vapour and certain noxious effluvia, and has its elasticity diminished. Boerhaave ingenuously confesses his ignorance on the subject, and Haller, after reviewing with his accustomed candour the opinions of his predecessors, coincides very nearly with the doctrine of Hales."

It was about this period that Black commenced his chemical discoveries, one of the most important and best established of which was, that a quantity of what was then termed fixed air, or as we now more

one of the most striking proofs of the neglect into which Mayow's works had fallen about the middle of the last century is the circumstance of his discoveries on air not having been alluded to by Pringle, in his address to the Royal Society, on presenting Priestley with the Copley Medal; Discourses, No. 1.

2 Statical Essays, v. i. p. 234..6..

3 Ibid. v. ii. p. 94, 100. et alibi.

+ Prælect. t. ii. § 203. cum notis ; t. v. § 625. cum notis et alibi.

Not. 40. ad Boer. Præl. t. v. § 625; El. Phys. viii. 3. 11, viii. 5. 19, 0. et alibi.