REPORT ON THE MARSUPIALIA. 141 



of which it sinks. In the male it is entirely expended in the supply of this muscle, hut 

 in the female Thylacine it soon emerges from midst the muscular fihres of the cremaster, 

 and is continued upon the superficial aspect of the muscle through the external 

 abdominal ring, and under cover of the sphincter muscle of the marsupium to the region 

 of the nipples, where it breaks up into a series of fine terminal twigs (PI. IV. fig. 4, g.c.n). 

 These are doubtless for the supply of the mammary gland, which in the specimen I 

 dissected (evidently a young virgin) could not be detected. 



The external cutaneous (PL V. figs. 5 and 6, e.c) is distributed to the skin on the 

 outer aspect of the thigh. It pierces the abdominal wall near the crest of the ilium, and 

 in the Cuscus it was observed to give several fine twigs to the panniculus carnosus. 



The anterior crural ' (PL IV. fig. 1, a.c.n, and PL V. figs. 5 and 6, a.c) in the 

 Thylacine arises in common with the obturator from the 3rd and 4th lumbar nerves, 

 whilst in the Cuscus it has an independent origin by two roots from the 3rd, 4th, and 

 5 th nerves. In both it proceeds backwards in the interval between the psoas parvus 

 and magnus, and, entering the thigh, at once breaks up into a large number of muscular 

 and cutaneous branches. 



During its course within the abdomen it gives a plentiful supply of twigs to the 

 psoas and iliacus muscles, and in the Cuscus a long slender twig (PL V. fig. 6, s) was 

 observed to spring from it, which pierced the abdominal wall to reach the sartorius. In 

 the thigh muscular branches are distributed to the sartorius, the pectineus, and the 

 various parts of the quadriceps extensor muscle. The cutaneous branches are the long 

 saphenous nerve and three or four twigs to the skin upon the anterior and inner aspects 

 of the thigh. 



The long saphenous nerve (PL IV. fig. 1, c.c.n) is a very constant nerve in all 

 mammals, although it varies very considerably in bulk and in its area of distribution. It 

 descends upon the inner aspect of the thigh and leg in company with the vein of the same 

 name, and dispenses numerous twigs to the skin. In the Thylacine its terminal twio-s 

 are lost in the integuments over the internal ankle. In the Cuscus, however, it is 

 continued downwards in front of the inner maleolus for the supply of the skin on the 

 dorsal aspect of the broad opposable hallux (PL VI. fig. 8, 3). Here it is joined by a 

 twig from a special nerve to the hallux (PL VI. fig. 8, 4) (derived from the internal 

 popliteal), and breaks up into three filaments ; of these one runs along each margin of 

 the digit, whilst the third proceeds along its middle line. On the dorsum of the foot it 

 effects a communication with the musculo-cutaneous nerve. 



A glance at the beautiful figures which accompany Ruge's paper 2 upon The Group of 



1 In the Ass, in which the lumbal nerves are six in number, the anterior crural nerve springs from the 3rd, 4th, 

 5th, and 6th nerves ; and in the Fox, in which the lumbal nerves are seven in number, it takes origin from the 4th, 

 5th, and 6th (Swan's Comparative Anatomy of the Nervous System). 



- Morphol. Jahrbuch, 1878. — Untersuchung fiber die Extensorengruppe am Unterschenkel und Fusse der Saugethiere 

 von Dr. Georg Ruge, Heidelberg. 



