102 ANATOMY OF THE WOOD RAT 



ward of the testis, is connected with the caudal mass of 

 the epididymis, approximately of equal size, by a single 

 canal, passing over the dorsum of the testis. From this 

 caudal mass extends the vasa deferentia (together with 

 the testicular artery), to its junction with the urethra just 

 craniad of the bladder. 



Craniad of the head of the epididymis and partly covering 

 it is a flat mass of fat, appearing somewhat glandular in 

 structure and possibly so in action as well. In the Neotoma 

 this mass of fat is relatively small, but in the sexually in- 

 active Homodontomys and Teonoma it is several times 

 larger. That the fluctuation in size of this fatty tissue is 

 correlated with sexual activity seems highly probable. 



Caudad of the corpora cavernosa the penis bends craniad, 

 and a second bend turns it caudad once more. These two 

 portions will be referred to as the proximal and distal tracts. 



The glans penis of each of the subgenera is illustrated. 

 It is, for the most part covered with illy-defined papilla. 

 In Neotoma it is roughly cylindrical, tapering gradually 

 and terminating in a sharply-decurved, soft spine. The 

 latter covers and partly closes the urethral orifice. Dor- 

 sad to this are two slight folds. In Teonoma the glans 

 is much smaller, though whether it is so characteristically 

 or merely because of sexual quiescence is unknown. The 

 slight wrinkling of its tip suggests the latter explanation. 

 It is a gradually tapering cone, ending in an acute, soft point 

 at the tip of which there is the urethral orifice. The glans 



Fig. 2\. a, Urogenital organs of sexually active male Neotoma. 



B, The same, of sexually inactive male Homodontomys, enlarged an 

 equal degree. 



C, Os penis of Neotoma. 



D, Penis of Teonoma. a, glans penis, b, prepuce (cut); c, M. compressor 

 urethrae; d, M. ischiocavernosus; e, crus of corpus cavernosum, /, Cowper's 

 gland; g, bulb of corpus spongiosvun; h, M. bulbocavernosus; i, M. sphincter 

 ani externus; j, prostate gland; k, neck of bladder (cut); I, ureters; m, 

 coagulating gland; n, seminal vesicles; o, fatty tissue; p, testis; q, epididy- 

 mis; r, vas deferens. 



