on the human urethra. 
193 
Fig. 1. A longitudinal section of one of the corpora caver- 
nosa, showing the course of the artery, branching through 
the trellis work. The part at A, has the central cavity 
exposed. This section is magnified two diameters. 
Fig. 2. A very small portion of the cellular substance of 
the same longitudinal section, taken from the part at A ; 
magnified fifteen times in diameter. 
Fig. 3. A small portion near B ; magnified fifteen times 
in diameter. 
Plate XXI. 
Consists of six figures, three of the corpus spongiosum 
urethrae, one of the internal membrane of the urethra, and 
two of the villi of the covering of the glans penis. 
Fig. 1. A transverse section of the corpus spongiosum ure- 
thrae, taken from the same penis as Plate XIX, Fig. 1. mag- 
nified four diameters, to show the parts more distinctly, par- 
ticularly the sections of the arteries going to the trellis work. 
Fig. 2. A small portion of the transverse section. Fig. 1, 
magnified fifteen diameters, to show the trellis work in the 
corpus spongiosum. 
Fig. 3. A longitudinal section of the same corpus spongi- 
osum and muscular coat of the urethra ; magnified fifteen 
times. 
Fig. 4. The internal membrane with the glands upon its 
surface, and the lacunas ; magnified ten diameters. 
Fig. 5. The covering of the glans penis for the papillas ; 
magnified ten diameters. 
Fig. 6. A smaller portion ; magnified twenty-five di- 
ameters. 
