C70 ANATOMY OJF VERTEBRATES. 



table sinuses, and projects beyond the proper erectile tissue of 

 the glans. Besides the usual muscles of the penis there is, in 

 Plantigrades, a pair arising from the sacrum diverging to include 

 the sphincter ani, and then continued on to the dorsum penis as 

 far as the bone. In the Otter the sperm-ducts have glandular 

 terminations. ' Between the two there is a small body or canal 

 which enters the urethra at the caput gallinaginis, but not with 

 the vasa deferential' 1 in this remnant of the protometra the 

 cor nu a are filamentary, as in Meles. In Mustela martes, also, 

 Hunter observes : ' There is a small cavity between the two 

 vasa deferentia, at their entrance into the urethra, which will 

 admit the small end of a small blow-pipe ; but I could not find 

 any natural opening into the urethra.' 2 



In the Dog- tribe the scrotum is more prominent than in Mus- 

 telines or Plantigrades. The prostates form a protuberant body, 

 and exude the secretion by several pores at the sides of the veru- 

 montanum. The spongy tissue of the urethra expands suddenly and 

 considerably at the base of the glans, which has an ossicle: the blood 

 is thence returned by two ' vena? dorsales penis ' : these are com- 

 pressed by the action of 4 levatores,' arising from the first caudal 

 vertebra, passing one on each side of the anal sphincter, then con- 

 verging to gain the dorsum penis, crossing the veins, and termi- 

 nating at the base of the bulbous part of the glans. As long as 

 the ' levatores ' retain the stimulus to contract, after coition, the 

 distended glans forms a mechanical impediment to retraction of the 

 penis from the vagina. 3 The ossicle is grooved for the urethra. 



The prostates are moderately large and lobulate in the Ichneu- 

 mons, in which Cowperian glands also exist. In the Suricate 

 (Rhyzana tetradactyla) the scrotum is as little marked as in 

 Mustelines : there are neither vesicular nor prostatic glands ; 

 but there is a pair of very large Cowperian glands, with the 

 usual muscular capsule, and with unusually long ducts, through 

 which the secretion is propelled to a dilatation near the distal 

 end of the urethra : behind their orifices a semilunar fold opposes 

 the retrograde passage of the secretion into the long tract of 

 urethra intervening between it and the neck of the bladder. 

 In the Zibet ( Viverra Zibetha) there is a small prostate : beyond 



1 c'cxxxvi. vol. ii. p. 74. See also CCXLI". p. 49. 



2 Ib. ib. p. 67. 



3 ' I laid bare the penis of a dog, almost through its whole length ; traced the two 

 veins that came from the glans and separated them from the arteries by dissection, 

 that I might be able to compress them without affecting the arteries. I then com- 

 pressed the two veins, and found the glans and large bulb became full and extended.' 

 xciv. p. 32. 



