C. M. Jackson W5 
extending in from the tunica albuginea (Fig. 4). The appearance of 
the corpora cavernosa in this region is in striking contrast to that of 
the corpus spongiosum, especially in injected specimens. Still more 
striking is the appearance of a specimen stained with osmic acid, in 
which the corpora cavernosa are stained jet black. Passing from the 
distal extremity, the corpora cavernosa gradually enlarge, and become 
more fibrous and vascular. The vessels are irregular venous channels, 
best developed in the center of each corpus, so that the adipose tissue 
Fig. 3. Cross-section through glans penis of a cat, near external meatus, vessels 
injected. x 40. Stained with haematoxylin. ep, epidermis; ur, urethra; 0, strip 
of epithelium connecting urethra with surface epithelium; sp, superficial integu- 
mentary plexus of vessels; dp, deep venous plexus, forming the cavernous tissue of 
the glands; op, os penis. 
i 
appears to become gradually crowded toward the periphery (Fig. 5). 
Toward the base of the penis the cavernous tissue increases steadily in 
amount, and the adipose tissue correspondingly decreases. In the 
proximal third, as a rule, a very slight amount of adipose tissue is 
present in the form of a few groups of fat cells, forming an imperfect 
peripheral layer, especially on the ventral side. Adipose tissue is never 
entirely absent. The cavernous tissue in this region is composed of 
typical irregular venous spaces, separated by fibrous trabecule in which 
the smaller arteries enter. The cavernous tissue differs from that of 
