2l8 
W. C. TWISS 
are transformed into the products of secretion such as fats, glycogen, pig- 
ments, etc., in the cells. But Altmann, besides claiming for his bioplasts 
the powers already noted, which are to a certain extent the same as those 
believed by modern exponents of the mitochondrial theory to reside in the 
mitochondria, held that the bioplasts are the morphological units of living 
matter, constituting the essential elements of protoplasm. The difference, 
in short, between Altmann 's hypothesis and the more modern theories of 
the mitochondria lies in the fact that the bioplasts were postulated to possess 
an independence and autonomy, to quote Regaud, which the mitochondria 
as cell organs are not thought to exhibit. 
Benda, in 1898, having devised a more specific and definite method of 
fixation and staining, may be regarded as the founder of the modern mito- 
chondrial theory. He introduced the terms mitochondria and Chondrio- 
miten, from fxiros a thread, and xo^bpiov a grain. Chondriosome and 
chondriocont, later introduced by Meves, have also come into use, the former 
being used synonymously with mitochondria, and the latter being applied 
by Meves to homogeneous threads. The collective term chondriome is also 
often employed. 
Regaud ('11) suggests the possibility that the mitochondria "fix" and 
"elaborate" the substances necessary for the functioning of the muscle 
cells, such as glycogen, and that they also perform a similar function in the 
case of the gland cells, such as the secretory cells of the kidney and of the 
salivary glands. He says: Les mitochondries sont les organites sur lesquels 
se fixent les substances destinies au fonctionnement chemique de la cellule; ces 
organites concentrent les substances fixees, les elaborent et les transforment en 
produits de secretion, auxquels ils servent meme de supports, dont ils sont les 
plastes." The mitochondria are ''les agents de V intussusception elective, 
c'est-d-dire, de V introduction dans la cellule des substances amenees par le 
sang.'' 
Dubreuil ('13) believes that the mitochondria are responsible for the 
production of fat in the cells, through a process of differentiation. Accord- 
ing to Dubreuil, a lipoid vesicle is first formed, this process being followed 
by the development of a fat droplet. The diagrams to illustrate this 
process, showing the mitochondria becoming vesicular and forming both 
hollow spheres and "hand-mirror-like" forms, exhibit a remarkable simi- 
larity to the series of changes which Guilliermond and others show in their 
illustrations of the production of plastids by the mitochondria in plant cells. 
Van der Stricht ( '09) has presented some very suggestive studies upon 
the genesis of yolk-spheres in the egg. He finds that the mitochondria are, 
at first, confined to a region around the nucleus from which they migrate 
outward and are gradually transformed into yolk-spheres. 
Lewis and Lewis ('15) have employed a novel method for the study of 
mitochondria with most interesting and suggestive results. Portions of the 
living embryo of the chick were segregated under aseptic conditions and 
cultivated in Locke's solution, in hanging drop cultures. In such cultures 
