Il6 PHILOSOPHICAL TKANSACTIONS. [aNKO 1704. 



we find in other animals; their upper parts dd are bulbous, and covered with 

 muscles cc, like the bulb of the cavernous body of the urethra in men: in other 

 animals, those parts of the corpora cavernosa penis are of a conical figure. The 

 muscles of the cavernous bodies of the penis in this animal having no connection 

 with the OS pubis, cannot apply the dorsum penis to the last named bone, and 

 compress the vein of the penis, so as to retard the refluent blood, and cause an 

 erection, as we have observed in other animals; but some large veins of the 

 penis here take a diflferent course, and pass through the middle parts of the bulb 

 KKC, fig. 4, and are only liable to the compression made by the intumescence 

 of these muscles cc, fig. 2, that inclose them. 



But the chief agent in continuing the erection of the penis in this animal, is 

 the sphincter muscle of its anus, or rather cloaca, to which the broad sphincter 

 muscle above-mentioned is continued, and does somewhat contribute. When 

 the penis is extruded from the cloaca, which must happen when it is erected, 

 the sphincter of that part necessarily embraces it ; the like must be done by the 

 sphincter muscle of the cloaca of the female in coition : on these accounts I am 

 apt to think that these animals are not very quick in that act. Besides, the 

 shape of the penis, (fig. 4) shows an unfitness for its retraction, till there is a 

 detumescence of its glans ab, which perhaps does not happen in these animals 

 till both male and female are satiated, as in dogs and other animals that have 

 bones in their penis, and have a bulbous intumescence of the glans in coition, 

 and no vesiculae seminales as in this animal, and also impregnate the female with 

 more than 2 or 3 at a time, as the opossum does. 



As the bulb of the cavernous body of the urethra in man is framed for the 

 use of the glans, to keep it sufficiently distended when required; so it seems it 

 is necessary to have two of those bulbs inclosed with their particular muscles ee, 

 fig. 2, in this animal, to maintain the turgescence of its doubled or forked glans 

 AB, fig. 4, when the penis is erected: in this distention of this glans penis of 

 this animal, the middle part of the orifice of the urethra, where the probe is seen 

 passing out of fig. 3, is necessarily compressed, as represented by d, fig. 4, and 

 two distinct apertures cc are left open, as appears by ab on each side its forked 

 glans. 



Those who suppose an aura seminalis of the male passes by the way of the 

 blood of the female to their ovaria, to fecundate the ova, will here meet with 

 an instance I must leave them to solve. For to what end has nature been at 

 the trouble of making double emissaries for the semen of the male opossum, as 

 though she designed the impregnation of a double uterus of the female ? 

 Certainly one passage in the glans penis would have been sufficient to convey 

 the semen masculinum to the mass of blood of the female in the manner they 



