DEPARTMENT OF EMBRYOLOGY. 105 



him, that the mitochondria are not directly concerned with speciaHzed 

 activities, such as conduction or secretion, but rather with some funda- 

 mental process common to all cells ; they probably participate in some 

 of the processes involved in cell metabolism and possibly in proto- 

 plasmic respiration. 



In its application to pathological conditions, the work on mito- 

 chondria puts at our disposal a new criterion of cell activity and cell 

 injury, which heretofore have been gaged almost exclusively by 

 nuclear changes. Mitochondria show deUcate sensitivity to patho- 

 logical changes and respond by variations in shape and size to injurious 

 influences, even before the nucleus. Furthermore, the indicator in 

 this case is cytoplasmic, and we may confidently expect it to disclose 

 facts which would never have been revealed by a study of the nucleus 

 alone. Favorable results have already been obtained by its applica- 

 tion to the study of exophthalmic goiter. 



Throughout Dr. Cowdry's paper there is clearly pointed out defi- 

 ciencies in our present information regarding the character and role 

 of mitochondria, and it abounds in suggestions and practical programs 

 for further investigations in this fundamental field. 



Another paper reviewing the status of mitochondria, or chondrio- 

 somes as designated in his terminology, is that of Professor Jules Dues- 

 berg. Investigators following the chondriosome problem will be espe- 

 cially interested in his discussion of the part played by these structures 

 in fertilization and in the process of differentiation, although in these 

 respects he does not reach positive conclusions. Benda's opinion that 

 chondriosomes are an idioplasmic substance is definitely supported 

 by Duesberg's description of the behavior of the male chondriosomes 

 in Ascaris during fertilization. An important step was made when it was 

 gradually shown that chondriosomes are constant in all spermatozoa of 

 all species, although varying greatly in shape and location in the differ- 

 ent species. The great majority of biologists originally accepted the 

 view that the nucleus is the carrier of the idioplasm, for the obvious 

 reason that in most cases only the nucleus of the spermatozoon was 

 detected in the egg. When it was shown, however, that in a large 

 number of both invertebrates and vertebrates the chondriosomes also 

 penetrate the egg, the monopoly of the nucleus as a carrier of the 

 idioplasm was brought up for reconsideration. Whereas the way 

 would seem clear for the hypothesis that the chondriosomes represent 

 the idioplasm contained in the protoplasm of the seminal cells, an 

 obstacle is met with in the discovery that the chondriosomal part of 

 the spermatozoon passes unchanged into only one of the two first 

 blastomeres (bat). Dr. Duesberg meets this difficulty by suggesting 

 that these blastomeres of the mammahan egg are not equivalent; 

 i.e., one may form the trophoblast, the other the embryo. The con- 

 stancy of the chondriosomes in the spermatozoon, the lack of a satis- 



