- ■ in regard to Respiration. ' 265 



we have seen, arc an organic tissue, and an earth entirely cal- 

 careous. Is the absorption of the oxygen of the atmosphere, 

 however, produced by, these two substances, or by one exclu- 

 sively of the other? I at first thought, that, to obtain a solu- 

 tion of this problem, it would be necessary to subject both 

 t<:) experiment ; and I began with the calcareous matter, be- 

 cause it could be easier employed for that purpose. As it 

 had all the essential relations with carbonate of lime, I was 

 enabled to ascertain, with great convenience, whether it pos- 

 sessed this absorbing power: in that case there was reason 

 to conclude, that the carbonate of lime of the shells had 

 the same ; but if carbonate of lime did not possess this 

 lacultv, it was clear that the absorption of the air by the 

 shells did not arise from the calcareous but the animal part, 

 and this is what I concluded; because the purest carbonate 

 of lime, cr)'Stallized and transparent, calcareous spar, kept a 

 long time immersed in common air^ does not occasion in it 

 the least alteration. 



I had a striking confirmation of this by some shells of the 

 hi'Ux pomatia and the helix 7iernoralis, which I found by 

 chijlnce in the garden, and which appeared to me to have 

 been along time deprived of their inhabitants, as I judged 

 from their being worn, and from the alterations they had 

 experienced : they had become lighter, and easily broke, or 

 were reduced to powder, between the fingers. The calcareous 

 matter refound by means of acids and fire, left me no 

 doubt in regard to their nature. I however found that they 

 had lost a great deal of their power of absorbing oxygen, 

 and that this loss was greatest in the shells which had been 

 most disorganized. It must therefore be admitted, that the 

 organization of the shells of testacea is the cause of this 

 absorption, independently of the calcareous matter, or at 

 least that without this organization the shells could not 

 produce that effect. In like manner, if these shells are pre- 

 .served in such a manner that they are not sensibly decom- 

 posed, even though kept several years, they still retain their 

 active property of speedily absorbing oxygen. 



Such, my learned friend, are the principles of which I 

 was desirous to connnunicate to you some idea. Though 

 the pulmonary respiration of this numerous species of ani- 

 lyials has been the principal object of my experiments for 

 several years, I wished only in this letter to give you a hasty 

 sketch of them, in order to show how living animals con- 

 tinually consume oxygen gas in a manner independent of 

 the lungs, and how they destroy it even after their death : 

 y.ou have seen it in cold-blooded animalsj as well as in 



worms 



