66 R. T. Anderson. 



Carpenter quotes a curious example of progressive albinoism in a 

 negro (the account was read by Dr. Inman at the Brit. Ass. Liver- 

 pool 1854; see Carpenter p. 984). 



In connection with albinoism the curious thing is the condition 

 of the Eetina, which contains no pigment. This absence of pigment 

 produces red eyes and a sensitiveness to bright light as well as pecu- 

 har oscillatory movements. 



Albinos see best in the twilight or night, the reflection of the 

 rays from the retina gives rise to indistinct images. It seems that in 

 certain animals that hunt at night the retina is rendered more sensi- 

 tive by the absence of pigment, or presence of white pigment. Albi- 

 noism is common in horses, oxen, rabbits fen^ets and other animals. 



The rat which was brought to me last winter was perfectly white 

 all over, the skin of the tail quite pale, and the eyes red, even though 

 the animal had been killed before I received it. The weight, length 

 and general conformation presented no unusual features. The hair 

 was examined under the microscope and compared with that of the 

 ordinary rat and the hair from the stomach of a lobster. The not- 

 ches of the core appeared much more distinct than in the hair of an 

 ordinary rat. 



I have nothing to say about the retina beyond the fact that 

 each was totally devoid of pigment. The lens was examined and 

 about this there is something to be said. It was round, or nearly 

 so, when examined from the front. Antero-posteriorly, however, the 

 lens appeared doubly conical. 



The apex of one cone stretched backwards, and the other apex 

 forwards. The diameter of the lens from apex to apex of the cone 

 was equal to the transverse (i. e. the vertical diameter). Now in an 

 ordinary rat the lens is, of course, somewhat flattened fi^om before 

 backwards so that the antero - posterior diameter is less than the 

 vertical or transverse. The lens in the albino was, therefore, nearly 

 spherical. 



The measurements in the albino were 



Anterio - posterior diameter 3 mm 



Vertical diameter 3 mm 



