ZOOLOGY. o5T 



number is somewhat greater than the second, and the heat developed by con- 

 traction ought to be admitted among the causes of this slight difference : these 

 two numbers are therefore sufficiently in accordance with each other. 



I have completed these researches by some new studies on induced con- 

 traction, that is to say, on the phenomenon of the irritation of a nerve in con- 

 tact with a muscle in contraction. A great number of experiments lately 

 made on the discharge of the torpedo, and on the analogy between this dis- 

 charge and muscular contraction, have led me to establish the existence of an 

 electrical discharge hi the act of muscular contraction. The general conclusion 

 to be drawn from these researches is, therefore, that the chemical action which 

 accompanies muscular contraction developes in living bodies, as in the pile or 

 hi a steam-engine, heat, electricity, and vis viva, according to the same mecha- 

 nical laws. 



Allow me to describe to you briefly the only one of these experiments 

 which can be repeated in a lecture, and which proves the principal fact of 

 these researches, although it is limited to prove that muscles in contraction 

 develope a greater quantity of carbonic acid than those in repose. Take two 

 wide-mouthed glass phials of equal size, 100 or 120 cub. centims. ; pour 10 

 cub. centims. of lime-water (eau de chaux) into each of these phials. Prepare 

 ten frogs in the manner of Galvani, that is, reducing them to a piece of spinal 

 marrow, thighs, and legs without the claws, which are cut in order to avoid 

 contact with the liquid in the phials. The cork of one of these phials is pro- 

 vided with five hooks, either of copper or iron, on w T hich five of the prepared 

 frogs are fixed. Through the cork of the other phial are passed two iron 

 wires, bent horizontally hi the interior of the phial ; the other five frogs are 

 fixed by the spinal marrow to these wires. This preparation must be accom- 

 plished as rapidly as possible, and both the phials be ready at the same instant, 

 and great care taken to avoid the contact of the frogs with the sides of the 

 phials or the liquid. TThen ah" is in readiness, with a pile of two or three ele- 

 ments of Grove, and with an electro-magnetic machine, such as is employed 

 for medical purposes, the five frogs suspended on the two iron wires are made 

 to contract. After the lapse of five or six minutes, during which time the 

 passage of the current has been interrupted at intervals in order to keep up 

 the force of the contractions, agitate gently the liquid, withdraw the frogs, 

 close rapidly the phials, and agitate the liquid again. You will then see that 

 the lime-water contained in the phial in which the frogs were contracted is 

 much whiter and more turbid than the same liquid contained hi the other 

 phial in which the frogs were left in repose. It is almost superfluous to add, 

 that I made the complete analysis of the air in contact with the frogs accord- 

 ing to the methods generally employed. 



OX THE ASSIMILATIVE POTTER OF VARIOUS FATTY BODIES. 



All fatty bodies do not possess the same power of assimilation ; some are 

 digested with an almost inexhaustible facility ; with others, on the contrary, 

 the organism soon arrives at what may be termed saturation ; so that after 

 a certain time the fatty body will be found in the excrements, almost un- 

 altered. 



