176 APPENDIX TO MEMOIR OF PELTIER. 



taken from anotber organ than the testicles be added, the movement is commu- 

 nicated to a still greater number, the expansion of the tufts increases, the oscil- 

 lation extends to half the length of the fibrils, and the posterior portion of the 

 zoosperms may then be perfectlj^ recognized; if a still more heterogeneous liquid 

 be addeil, such as river or pond water, the movement becomes general and the 

 whole body of the filament oscillates. After a few instants, some of these fila- 

 ments are seen to detach themselves from the primitive nucleus ; presently all 

 successively quit it, become so many complete zoosperms, and leave the parent 

 globule covered with brownish points where they had been attached. 



Once become free, the zoosperms undergo new transformations ; their anterior 

 part bends in an arch more or less elongated ; this arch, by closing, constitutes 

 a ring in some and an oblong mesh in others. A little later their anterior part 

 has assumed the shape of a cupel, fringed with vibratile cilia ; but before enter- 

 ing into this last state, these zoosperms have passed through intermediate forms, 

 giving them the ajipearance of different animalcules, by which circumstance 

 observers have been often deceived. Such, according to the researches of Peltier, 

 are the successive transformations presented by the zoosperms of the frog. 



Structure and contraction of the muscles. — Peltier also occupied himself 

 with the structure of the muscles and the phenomenon of contraction. He even 

 availed himself of several different methods, that he might study them with 

 greater profit. Sometimes he simply examined the muscular fibres with the 

 microscope, sometimes he proceeded by crushing them on the porte-object glass; 

 again, he unravelled them by means of the finest needles. He often operated 

 also on muscles desiccated by heat, for this process also yields good results. He 

 studied likewise the structure of the muscles in certain microscopic animals 

 which have muscles in a rudimentary state, and composed of one, two, or three 

 fibrils. In a word, he had employed all the means which science could furnish 

 him, and the following are the results to which he Avas coirducted :* 



The muscles are composed of distinct cylinders, of a diameter of from J^ to 

 3Q of a millimetre. S<?en with the microscope, these cylinders seem divided by 

 rather transparent longitudinal lines and by darker transverse lines. This 

 causes them to appear somewhat like an assemblage of small graduated scales 

 of a perfect regularity. The cylinders in question are formed of fibrils in juxta- 

 position, while the fibrils themselves are constituted by a tube filled with minute 

 grains, the diameter of which varies, in diflerent animals, from -^^-^ to ^3^0 ^^ ^ 

 millimetre. 



In studying these fibrils it is seen that the globules are ranged in succession 

 one above the other in their sheaths, that they touch and press one another, 

 Avhile the globules situated in the same transverse range, and pertaining each to 

 a different tube, are separated by a double membrane extremely transparent. 

 When a ray of light traverses a muscular fibre, diti'raction takes place quite 

 around each globule, except at the point of contact of the globules superposed 

 in the same sheath. It thus forms an image unequally illuminated, being less 

 so at the part in contact than in the rest of the outline of the globules. Hence 

 it results that the transverse lines which connect all these obscure points are 

 darker than the longitudinal lines; and from this we see in what consisted the 

 error of the pliysiologists who thought that these transverse fibres were formed 

 by nervous filaments, woimd in a helix around the muscular fibre. 



The globules of the elementary fibrils are strongly adherent to one another 

 and to tlieir sheaths, for it is very rare to find portions of the latter devoid of 

 their globules. 



When certain microscopic animals are deprived of life by long* inanition, the 

 whole contractile membrane is seen to be formed of aligned globules. In this 

 case also the diflerent phases of the phenomenon of contraction may be followed 

 with facility. It will be seen that the aiTangement in zigzag has here replaced 



* Annates des Sciences Nuturclles, 2ci series. Zoology, vol. ix, p. 89. 



