use of any particular sire, or by abnormalities in the breeding 

 tract noted by rectal or physical palpation." 



The observations of Williams (19) in a pure bred dairy herd 

 bring out quite clearly the relation of the bull to the dissemination 

 of genital infections. The bulls in this particular herd were ab- 

 normal in many respects, as demonstrated by pathological changes 

 in their genital organs, bacterial invasion of the parts, abnormali- 

 ties of the semen and spermatozoa, and the probable transmission 

 of infection to the females. Several of the sires from this herd 

 furnished much of the material for the early basic work of this 

 investigation. Since then the tracts of other sires have been worked 

 upon with quite similar or identical results. 



To summarize the work already done, most investigators have 

 considered the bull as merely a mechanical carrier of Bact. abor- 

 tum infection, though all are more or less suspicious of his ability 

 to become an active spreader. Schroeder, however, states that the 

 organisms are eliminated Avith the semen, but infection of the fe- 

 male occurs secondarily through the digestive tract by contamina- 

 tion of the food with the semen. Other investigators bring out 

 fundamental points demonstrating the importance of other organ- 

 isms than the Bang bacillus and call attention to the need of a 

 more thorough study of the anatomy, physiology, and pathology 

 of t.he male genital tract. 



Any study of the genital organs must of necessity rest funda- 

 mentally upon a thorough knowledge of the anatomy and phy- 

 siology of those parts. Too few of us have stopped to consider 

 thei^e questions thoroughly, with the result that our ideas on the 

 problem are more or less vague. It is much easier to understand 

 why abnormal spermatozoa occur so frequently, or changes take 

 place in the semen with death or weakening of the germinal ele- 

 ments, if we realize or stop to consider the highly differential pro- 

 cess of spermatogenesis, and the various structures which contrib- 

 ute to the formation of the semen. AVe must come to realize that 

 each part of the genital tract is essential to the normal functioning 

 of the whole, and that the genital tract and rer)roduction are in 

 turn dependent upon the proper functioning of the entire body. 



Walker (20) emphasizes the importance of a thorough knowledge 

 of physiology' in stating, ''Although the subject of sterility has 

 attracted the attention of the medical profession; and although 

 much has been written on its causes and treatment, it cannot be 

 claimed that the practical results olitaincd up to the present time 

 are satisfactory, or that when consulted for sterility, the medical 

 man of today can hold out to his patient much more hope of suc- 

 cessful treatment than the medical man of fifty years ago. Our 

 failure in this respect is in the main due to an ignorance of the 

 physiology of reproduction." 



To bring out some of these points, the anatomy of the tract will 

 l)e reviewed briefly, together with the physiology of reproduction, 

 and the various factors which should be considered in a studv of 

 the problem. 



