306 



PHYSIOLOGY OF GONADS 



more to the domain of comparative mor- 

 phology. The basic lessons already have 

 been learned from a few species, and only 

 the jDrovision of an unusual specimen for 

 study could be expected to aid the endo- 

 crinologist. 



Interest in the effects of cryptorchism has 

 shifted in the 20 years following jNIoore's 

 (1939) summary in the second edition of 

 this book; at that time, the main interest 

 in the cryptorchid testis was in its capacity 

 for hormonal production. At present, the 

 chief concern is with its capacity for sper- 

 matogenic function. Despite some labor and 

 much discourse, the treatment of crypt- 

 orchism in the human is not satisfactory. 

 Controlled methods of management based 

 on a reasonable working hypothesis have 

 not been evolved, so that a definitive evalu- 

 ation of results in terms of fertility is im- 

 possible. 



The architecture of the testis has been 

 described in terms of structural pattern and 

 composition adapted for the formation and 

 transport of sperm and for hormonal pro- 

 duction. The influences of the circulatory 

 and the nervous systems on testicular func- 

 tion have received uneven consideration. 

 The former system is essential for testicular 

 function; not only does it bring the neces- 

 sary gonadotrophic hormones to the testis 

 but, just as important, it provides food- 

 stuffs and oxygen and carries away metabo- 

 lites. The testis is extremely sensitive to 

 derangement of its blood supply. The pe- 

 ripheral nervous system, however, appears 

 to be relatively unimportant to the post- 

 natal well-being of the testis. 



The compartments of the testis are dis- 

 cussed in two sections of this chapter. The 

 germinal epithelium produces sperm, and it 

 is with regard to this compartment that 

 major advances have been made. Quanti- 

 tative cytologic studies have unraveled the 

 spermatogenic cycle and have provided de- 

 tailed information on spermiogenesis. These 

 studies are tedious and require painstaking 

 techniques, but there is at present no other 

 way to obtain quantitative information. 



The hormonal compartment of the testis 

 has been further clarified by morphologic 

 methods, but the greatest advances have 

 been made by chemists. The biogenesis of 

 male hormone has been worked out and is 



discussed in detail in the chapter hj Villee. 

 So far, the hormones manufactured by the 

 testis have been shown to include only 

 steroids. A flare of interest in a water-solu- 

 ble hormone, namely inhibin, was short- 

 lived, and this issue has been dormant in 

 the past decade. 



The next two sections of this chapter, the 

 control of the testis by the pituitary, and 

 the effects of male hormone and other ster- 

 oids on the testis are representative of 

 classic endocrinology. The dual concept of 

 testicular control by means of follicle-stimu- 

 lating hormone (FSH) and luteinizing hor- 

 mone (LH) for the tubular apparatus and 

 the Leydig cells, respectively, is less secure 

 than it was believed to be in 1939. Interest 

 in the fractionation of pituitary gonado- 

 trophins waned in the 1940's, and investi- 

 gators were unable to obtain purified FSH 

 and LH for experimental study. Further- 

 more, the discovery that testosterone and 

 other steroids maintained spermatogenesis 

 in the complete absence of gonadotrophins 

 became an irritant to the dualist's com- 

 posure. Intensive effort in this area has re- 

 moved some difficulties, but it has not 

 solved the problems. Recent studies have 

 shown that male hormone is needed for 

 spermiogenesis and gonadotrophins for co- 

 pious spermatogenesis, but there the prob- 

 lem rests. 



The effect of alterations in the endocrine 

 system on the testis is discussed briefly. Ex- 

 tremely little has been done in this area ex- 

 cept for the influence of altered thyroidal 

 states. As will be seen, the thyroid can exert 

 some influence on testicular function, but 

 this depends largely on the species studied. 

 Further understanding will evolve as more 

 species are studied. 



The last sections in the chapter deal with 

 disorders and tumors of the testis. Dis- 

 orders of the testis, chiefly hypogonadal 

 states, are important in both veterinary 

 and clinical medicine. Study of some of 

 these disorders has greatly clarified normal 

 jihysiology. A brief survey will be given of 

 this aspect to emphasize the pituitary regu- 

 lation of testicular function as shown by the 

 effects of certain spontaneous disorders of 

 the pituitary. Brief mention will also be 

 made of the awareness of the increasing im- 

 ])()rtanco of genie factors and of the fetal 



