212 MR. J. B. SUTTON ON DISEASES OF [-Apr. 20, 
contiguous margins; the remaining digits were normal.” I[ re- 
member examining the specimen, at the time Mr. Forbes noticed it, 
in the Prosector’s room, and was impressed with the perfect sym- 
metry of the malformation. 
Since then one other example of malformation in the manus of a 
Monkey has occurred. A Gibbon (Hylobates leuciscus), which lived 
in the Gardens a few months, was found to have a supernumerary 
finger on each hand. In this case the additional fingers possess a 
metacarpal bone which was attached to the ulnar side of the meta- 
carpal of the fifth digit, and it seems as though the supernumerary 
bone was formed as a result of bifurcation of the distal end of the 
fifth one. The carpal bones do not present any abnormality. So 
few examples of polydactyly in Quadrumana have been noticed that 
the case before us is worthy of record. 
Fig. 5. 
A follicular cyst from a Prehensile-tail Porcupine, Sphingurus prehensilis. 
The upper figure represents the jaw after the remoyal of the cyst. 
w, the inferior dental nerve. The lower drawing is the cyst with the teeth 
projecting into it. The arrow marks the position of the mental foramen. 
As an additional illustration of symmetry in disease, the following 
ease is of value. A  Prehensile-tailed Porcupine died from the 
effects of a large abscess on each side of the mouth. These had 
burst externally, giving rise to deep sinuses. A probe passed into 
each gave evidence of necrosed bone; and at first sight the case 
seemed to be one of alveolar abscess consequent upon diseased teeth, 
a condition of things exceedingly common in animals. On examining 
the mouth I failed to find the lower incisors; this was very sin- 
gular, because the bone at the symphysis was quite normal. On 
tracing one of the sinuses by dissection, it was found to lead into 
the mental foramen, and thence into a cavity occupying the body of 
