OF DIDELPIIYS VIRGINIANA. 45 



ternal wall of the meatus, running across to meet a fold of the lobe itself. A triangular 

 fossa is bounded by these two folds and the anterior margin of the ear. (Fig- 4.) 



The ear and other naked parts of the body appear to have a low grade of organization, 

 or at least less vitality than ordinary. Under unfavorable conditions, as when the animal 

 is closely confined for a length of time, the ears, tail and digits are susceptible of ulcera- 

 tion, and often rapidly slough away. The Schneiderian membrane is peculiarly subject to 

 haemorrhage ; epistaxis may be brought about, for example, by the passage of a current 

 of electricity, or by very moderate violence. 



The ano-genital orifice, as usually observed, has a puffy, inflated, almost prolapsed ap- 

 pearance, as if imperfectly guarded by the sphincter : the penis is almost alwa^'s, however, 

 withdrawn. The abdominal scrotum is loosely pendulous, almost pedicellate; its livid 

 bluish color appears through the short fur. It is capa])le, however, of marked contraction ; 

 and the testicles may be closely drawn up. The pouch may be detected at a very early 

 age ; but in the virgin, though full grown, female, it is never conspicuous, and would es- 

 cape observation unless sought for; it appears simply as a slight duplication of the skin, 

 capable of admitting the tips of two or three fingers. It rapidly increases with use, and 

 attains a large size, after which, though diminishing somewhat, it never returns to its 

 original condition. The furry lining, at first colored like the rest of the belly, acquires 

 during the pouch-gestation a fulvous or reddish hue ; the nipples, at first small, concealed 

 in folds of the skin that are scarcely perceptible, become very prominent, and are sur- 

 rounded by a naked aureole. There are thirteen nipples, one central, the rest disposed 

 in a circle. The lip of the pouch can be brought very near, if not in actual apposition 

 with, the genital orifice. The transfer of the newly-born young to the pouch has })een 

 shown to be accomplished by the voluntary act of the parent, with lips or paws, probably 

 the former. 



The reproduction of the opossum, for a long time a subject of wild or fanciful specula- 

 tion, has been satisfiictorily determined by the researches of Dr. Bachman and others : 

 to which, however, it would be out of place to more than allude in the present connection. 

 The full history is given in the papers of this gentleman, already cited. Among the 

 man}^ curious beliefs that still pass current Avitli the vulgar upon this subject, may be 

 mentioned one that ascribes to the opossum, in consequence, doubtless, of the bifurca- 

 tion of the penis, a coitus with the nostrils of the female ; sul)sequent sneezing, on her 

 part, upon the teats of the pouch causing the young to grow there. 



The opossum is extremely tenacious of life. It is, in fact, rather difficult to kill one 

 for dissection without mutilation of some part. In consequence of the shape of the parts, 

 it is not easy to reach and pierce the medulla ; a better way is to open the heart with a 

 slender bistoury introduced between the ribs. I found poisoning with cyanide of potas- 

 sium to be the most convenient method, with the additional advantage of afTording a 

 means of studying the operation of that very violent poison ; but for rapid efifect a larger 

 quantity is required than would be expected to suffice ; perhaps fifty times the amount 

 that would almost instantly kill a pigeon. The most noticeable effects are at first profuse 

 salivation, then unsteadiness of gait and general tremulousness, succeeded by clonic spasms 

 alternating with perfect rigidity ; ending with complete relaxation, accompanied by copi- 

 ous alvine and urinary evacuations. The time required is from five to fifteen minutes, 

 according to the dose, and strength of the subject. 



UEMOIRS B08T. 800. NAT. HIST. VOL. II. 12 



