32 



when first examined, but the motion did not sursdve for any great 

 length of time. Even a small percentage of motionless sperms or 

 of those sho^\^ng lowered vitality is a considerable factor in 

 potency. xVlthough millions of the germinal elements are ejacu- 

 lated into the vagina, large numbers of them are destroyed or be- 

 come motionless there, and a small number is left behind in the 

 cervix and uterus ; so that even though but a single sperm is 

 required for fertilization, the chances of impregnation are dimin- 

 ished in proportion to the number of dead or defective sperms. 



Aspermia: Absence of spermatozoa in the semen is rarely en- 

 countered, and is probably due either to total cessation of sperma- 

 togenesis, or to an obstruction at some point in the system of 

 excretory ducts. I have seen but one case of this character. The 

 semen of this bull was greatly increased in amount, and of a thin 

 watery consistency. Due to lack of cooperation on the part of the 

 owners, the tract could not be obtained for study. Oligospermia, 

 or a diminution of the number of spermatozoa, is quite common, 

 and is undoubtedly associated with defective spermatogenesis, 

 either as a result of poor mitosis of the seminal epithelium, or 

 degeneration of the elements before maturity. This condition may 

 vary from the finding of only occasional dead sperms in the field, to 

 but a slight decrease in the usual number of normal sperms 

 observed. 



Abnormalities in morphology may be classified into immature 

 types, and deformities or imperfect development of the head and 

 tail. Defective spermatogenesis occurs so frequently that it is 

 not surprising to find spermatozoa in various stages of develop- 

 ment cast into the excretory ducts. The various stages passed 

 through in the development, from spermatogonia to adult sperm, are 

 numerous, and it therefore is to be expected that we should see in 

 abnormal semen many different immature forms. No classification 

 of the various types can be made, but a clearer understanding of 

 them can best be obtained by a review of the process of spermato- 

 genesis. 



Spermatocytes and spermatids are seen in the more severe types 

 of defective spermatogenesis, and are relatively uncommon, while 

 the more mature forms that result from the transformations of 

 spermatid to adult cell are very often seen. Some of these inter- 

 mediate types are large oval cells without distinct nuclei and as a 

 rule with poorly developed tails. Cells with no tails or distinct 

 nuclei, those with protoplasmic appendages to the head or tail, and 

 various other types, are occasionally encountered. IMost of these 

 are motionless and incapable of producing impregnation. Others 

 are active, but survive a comparatively short time. According to 

 Gary, the production of the immature cells is an effort on the part 

 of the testes to sunplv an abnormal demand, and their presence 

 indicates that the fertility of the semen is impaired. 



The deformities, which may be divided into cephalic and caudal 

 groups, are also the product of defective spermatogenesis, or they 



