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Show 1886.] MAMMALS IN THE SOCIETY'S GARDENS. 211 curious deformity, for at the junction of the upper and middle third the shaft was bent almost at a right angle. The corresponding bones of the opposite side presented precisely similar lesions. The sebaceous glands of the skin very frqeuently in the human subject suffer obstruction of their excretory duct. The result is that the gland continues to secrete, but the outlet being closed, the sebaceous matter accumulates until at last a definite swelling results, which may remain of insignificant proportions, or attain a diameter of two or three inches in exceptional cases. Technically such swellings form one of a group known as " retention cysts." The museum of the Royal College of Surgeons possesses some specimens of symmetrical sebaceous cysts growing from the wings of Wood-Pigeons. The specimens were" presented by Mr. Tegetmeier. It appears that in certain seasons a large number of birds are found with swellings such as these on the wings, legs, and feet. A Cockateel, Cdvpsitta notm-hollaiidim, with symmetrical sebaceous cysts on its wings. An excellent example of this affection has recently come under my notice in a Cockateel, Calopsitta novce-hollandia. In this pretty bird there has developed on the inner surface of each wing a sebaceous cyst. The position, size, and shape of the " swelling" in the two cases exactly correspond, as may be seen on reference to the drawing (fig. 4). The specimen serves as an excellent illustration of symmetrical disease. Malformations are frequently as symmetrical as tumours and skin eruptions. Mr. Forbes has recorded in the 'Proceedings' of this Society (1882. p. 442) an example of webbed fingers in a Pithecia satanas. " Tbe third and fourth digits of the manus on each side were completely connected down to their tips by a fold of nude skin, with their nails closely apposed, though not connected, along their |
