37& 



NATURE 



{August 1 6, 1888 



kept shut, I was led to think that it might be breathed with 

 safety. I found, for example, that when sparrows died in it in 

 ten or eleven seconds, they would live in it for three or four 

 minutes, when the nostrils were shut by melted suet. And I 

 convinced myself that the chan je produced on wholesome air by 

 breathing it, consisted chiefly, if n it solely, in the conversion of 

 part of it into fixed air. For I found that by blowing through a 

 pipe into lime-water, or a solution of caustic alkali, the lime was 

 precipitated, and the alkali was rendered mild. I was partly 

 led to these experiments by some observations of Dr. Hales, 

 in which he says that breathing through diaphragms of cloth 

 dipped in alkaline solutions made the air last longer for the 

 purposes of life." 



Fifteen years afterwards — namely,in 1772 — Joseph Priestley exa- 

 mined the chemical effects produced by the burning of c indies 

 and the respiration of animals upon ordinary air ; and he made 

 the important discovery that, after air had lost its power of sup- 

 porting combustion, as by the burning of candles, this property 

 might be restored by the agency of plants. Pushing his experi- 

 ments still further, he found that air, deteriorated by the 

 breathing of animals, might again become suitable for respiration 

 by the action of plants. In these experiments he employed 

 mice for ascertaining how far an air was impure or unfit for 

 respiration. In 1774, Priestley obtained oxygen by heating red 

 precipitate by means of the sun's rays concentrated by a burning- 

 glass. This led to an investigation of the constitution of the 

 atmosphere, and it was shown that it was not a homogeneous 

 elementary body, but consisted of two gases, and that its con- 

 stitution was remarkably uniform. Priestley snowed that by fer- 

 mentation, combustion, the calcination of metals, and respiration, 

 the air lost a portion of one of its constituents, oxygen. 



Thus the chemical researches of Black and Priestley proved 

 that in respiration oxygen was consumed and carbonic acid 

 produced, although the latter fact, owing to the theoretical 

 views of Priestley as to phlogiston, was not fully appreciated 

 by him. 



Within a year after Priestley's discovery, a paper on respira- 

 tion was written by Lavoisier (1743-94), in which he showed 

 that Priestley was correct in stating that the air lost oxygen in 

 breathing, but Lavoisier specially pointed out that it had gained 

 carbonic acid. No doubt Lavoisier was well acquainted with 

 Black's researches, as is shown by the correspondence between 

 these distinguished men. Lavoisier was the first, however, to 

 make a quantitative examination of the changes produced in the 

 air by breathing. In 1780, he performed a remarkable experi- 

 ment, in which a guinea-pig was confined over mercury in ajar 

 containing 248 cubic inches of gas consisting principally of 

 oxygen. In an hour and a quarter the animal breathed with much 

 difficulty, and, being removed from the apparatus, the state of 

 the air was examined. Its bulk was found to be diminished by 

 8 cubic inches, and of the remaining 240 inches, 40 were absorbed 

 by caustic potash, and consequently consisted of carbonic acid. 

 Still later, he performed a more accurate experiment, giving 

 quantitative results. During 1789 and 1790, by a special ap- 

 paratus, Lavoisier and his friend Seguin attempted to measure 

 the changes in the air produced by the breathing of man. These 

 researches are not of value so much for the results they gave as 

 for the method employed. Lavoisier constructed a still more 

 elaborate apparatus, with which he began experiments. This 

 research, however, he never finished, as, in 1794, he fell a 

 victim to the blind fury of Robespierre. It is narrated that he 

 earnestly requested a respite of a few days to give him time to 

 prepare for publication the results of his investigations. This 

 was denied, and thus perished one of the greatest scientific sons 

 of France. 



Stephen Hales (1677-1761) attempted to measure the amount 

 of aqueous vapour given off by the lungs by breathing through a 

 flask filled with wood-ashes, which absorbed the moisture, and he 

 estimated the amount at about 20 ounces in twenty-four hours. 

 Similar observations were afterwards made by Menzies and by 

 the eminent surgeon, Mr. Abernethy. Lavoisier also attacked 

 the problem by an indirect method. Thus he determined the 

 quantity of oxygen consumed and of carbonic acid produced, 

 and, assuming that the amount of oxygen' was more than 

 sufficient to form the carbonic acid, he came to the conclusion 

 that the excess united with hydrogen in the lungs, and passed 

 off as water. As may be supposed, this method gave widely 

 different results. 



Various other attempts were made to estimate the amount of 

 the respiratory changes. In particular, Sir Humphry Davy, in 

 March 1798, investigated the physiological action of nitrous 



oxide gas. In this research, published in 1800, he began by 

 observations upon animals ; and observations as to the effect of 

 the gas on life, on muscular irritability, on the action of the 

 heart, and on the colour of the blood are recorded with great 

 precision. He then passed on to observations on the respiration 

 of hydrogen, and this led him to a repetition of the experiments 

 of Lavoisier and Goodwin. Next he subjected himself and friends 

 to experiment, and recorded a number of interesting physiological 

 and psychical phenomena. This research is of great historical 

 interest as being the first leading to the discovery of a method 

 of producing anaesthesia, or insensibility to pain, by breathing 

 vapours or gases. 



Another eminent man who contributed largely to the physio- 

 logy of respiration was Lazarus Spallanzani, who was born in 

 1729 and died in 1799. He was educated under the direction of 

 the Jesuits. When about sixteen years of age he went to Bologna, 

 and studied at that University, specially under the tuition of his 

 cousin, Laura Bassa, a woman celebrated in her day for eloquence 

 and scientific knowledge, and who was then a Professor in the 

 University. His biographer, Senebier, says : — " Under the 

 direction of this enlightened guide he learned to prefer the study 

 of Nature to that of her commentators, and to estimate their 

 value by comparing them with the originals they professed to 

 describe. The scholar at once perceived the wisdom of these 

 counsels, and quickly experienced their happy effects. He 

 evinced his gratitude to his instructress in a Latin dissertation 

 published in 1765, which was dedicated to Laura Bassa, and in 

 which he recounted the applauses she received at Modena when, 

 entering the hall, where her pupil, on being appointed a 

 Professor, was defending a thesis, ' De Lapidibus ab Aqua 

 Resilientibus,' she opposed it with the graces of an amiable 

 woman and the wisdom of a profound philosopher." 



Spallanzani became Profes or of Logic, Mathematics, and 

 Greek in Reggio in 1754, and about this date he published re- 

 searches on Infusoria. In 1760, he became Professor in the 

 University of Modena. In 1765, he showed that many micro- 

 scopic animalcula were true animals, and in 1768 he published 

 his celebrated researches on the reproduction of portions of the 

 body removed from worms, snails, salamanders, and toads. He 

 paid special attention to the great question of spontaneous 

 generation, showing that infusi >ns of animal and vegetable sub- 

 stances exposed to a high temperature, and hermetically sealed, 

 never produced living things. He also investigated respiration, 

 more particularly in invertebrates. He proved that many such 

 animals breathed by means of the skin as well as by the special 

 breathing organs. He placed many animals, but more especially 

 different species of worms, in atmo pheres of hydrogen and 

 nitrogen, and found that, even in these circumstances, carbonic 

 acid was produced. He also showed the production of carbonic 

 acid by the dead bodies of such animals, and reasoned from this 

 that the carbonic acid was produced directly from the dead 

 tissues and not from the action of the oxygen of the air. He 

 contrasts the respiration of cold-blooded and warm blooded 

 animals, and shows the peculiarities of respiration in hibernating 

 animals. Nor were these by any means superficial observations. 

 They were usually quantitative, and by the use of the eudio- 

 meter, he analyzed the air before and after respiration. 

 Probably the most important contribution made by Spallanzani 

 to the subject was showing what he states in the following 

 paragraph : — 



"I inquire not here why the quantity of carbonic acid gas was 

 greater in azotic and hydrogen gas than in common air. I shall 

 only conclude, from these experiments, that it is clearly proved 

 that the carb mic acid gas produced by the living and dead snails 

 in common air resulted not from atmospheric oxygen, since an 

 equal and even a greater quantity of it was obtained in azotic and 

 hydrogen gas ; consequently, in the oxygen gas destroyed by the 

 presence of these animals, its base alone is absorbed by them 

 either during life or after death." 



But Spallanzani supposed that the carbonic acid thus produced 

 was formed by digestion in the stomach, passed through the 

 tissues, and was then exhaled. Thus he missed a great step in 

 discovery — namely, that the carbonic acid is produced by the 

 tissues themselves. It was, however, pointed out in 1823, by W. 

 F. Edwards, in his work on the " Influence of Physical Agents 

 on Life," that the amount of carbonic acid produced by animal 

 breathing was too great to be accounted for by the amount of 

 oxygen in their lungs at the beginning of the experiment, or by 

 carbonic acid supposed to be in the stomach. The importance of 

 this observation will be seen when we discuss the phenomena of 

 the breathing of the tissues. 



