262 Letter of Spallanzani to C. Senelier 



remarked in the circulation, in consequence of the great 

 affinity between these two functions. Being desirous to ex- 

 ajnine them thoroughly, I kept in my house for five years 

 the five species of these animals found in Italy. By making 

 researches in regard to their respiration I had still another 

 object in view, which was to study the habits of this class 

 of animals, and every thing that might be interesting to 

 their history, because too little known, or not sufficiently 

 explained. Having, therefore, near me this great number 

 of animals, and having observed them during different sea- 

 sons of the year, and seen them in their natural retreats, I 

 was able to accomplish my plans as I wished. 



As the event must be curious, you will remember my 

 jnarmot, w hich was so lethargic during the severe winter of 

 1 793 ; I then kept it for four hours in carbonic acid gas, the 

 thermometer marking — 12". It continued to live in this gas, 

 which is the most destructive of all : a rat, at least, and a 

 bird which I placed in it perisijed in an instant. It appears, 

 then, that its respiration was suspended during that time. 

 I submitted to the same experiment bats which were in the 

 same lethargic stale, and the result was the same. I then 

 continued my experiments. I preferred these flying animals 

 to t' e marmot, apprehending that this animal might fall a 

 sacrifice to these trials and perish, because I had only two, 

 on w hich I had other experiments to make, whereas I had 

 in my possession a great number of bats. 



I u as therefore desirous to know, whether when respira- 

 tion was suspended in these animals a production of carbo- 

 nic acid would be effected by the organ of the skin. I then 

 substituted azotic for carbonic acid gas, in order that the 

 result might not be doubtful. I placed in this gas two bats, 

 the thermometer being at — 9°. At the end of two hours I 

 look ihcm out, and having gradually introduced them into a 

 warmer medium, they gave evident signs of life: but I 

 found no carbonic acid gas in the azotic gas ; which made 

 me conclude that this temperature was too low for the ex- 

 halation of it, I continvied these experiments at a tempera- 

 ture successively higher to — 3, by which means ^^^ of car- 

 bonic acid gas were produced, though the lethargy of these 

 animals was still strong;. 



In this state of things I repeated the experiment under 

 the same circumstances, only I rembved the bats into an- 

 other vessel full of common air; but I then found not only 

 the production of 3^ hundredths of carbonic acid gas, but 

 also the destruction of 5 hundredths of oxygen gas. Though 

 these two small quadrupeds were in respirabJe air, their pro- 

 found 



