1892.] The Cerebrum of Ornithorhynchus paradoxus. 163 



centre of a hollow metallic sphere, which was connected with the 

 Sprengel pump and surrounded with cold water, and were allowed 

 to cool. The temperature of the cooling globe was read off at equal 

 intervals of time by means of a thermo-electric junction ; and from 

 these readings the absolute loss of heat per unit of cooling surface, 

 per unit difference of temperatures of surface and surroundings, per 

 unit of time, is calculated. 



The details of the apparatus and method of experimenting are 

 given in the paper. It is enough to say here that the globes were 

 used with their surfaces in two different conditions : (1) Thinly 

 coated with lamp-black, and (2) silvered and brightly polished ; and 

 in both conditions the absolute loss of heat, both in air and in 

 vacuum, more or less complete, was determined. The tables and 

 curves attached to the paper give the details of the results. 



To quote one or two examples : With the sooted surface a total 

 loss of heat by convection and radiation of 3'42 x 10~* c.g.s. units 

 per square centimetre, per second, per 1 C. of difference of tempera- 

 tures of globe and surroundings, was observed with a difference of 

 temperatures of 100 C., and with the surroundings at about 14 C. 

 Under similar circumstances the radiation in vacuum of ^M (half-a- 

 millionth of atmospheric pressure of non- collapsible gas) was about 

 1-40 xlO~ 4 . 



Taking a silvered and brightly-polished surface under the same 

 circumstances, the loss in full air was 2'30x 10~ 4 c.g.s. ; and with 

 the highest vacuum and brightest polish obtained, it was reduced 

 1'80 x 10~* with in this case a difference of temperatures of 180 C. 

 The loss with 100 C. difference would be considerably less, but is not 

 known experimentally at present. 



The author returns thanks to Mr. James H. Gray, M.A., B.Sc., 

 for excellent assistance given ; and expresses himself most deeply 

 indebted, both for assistance in experimenting and calculating of the 

 results, and for most valuable and ingenious aid of various kinds 

 during the course of this work, to hia friend Mr. A. Tanakadate, now 

 Professor in Tokio, Japan. 



XVI. " The Cerebrum of OrnitJiorJiynchns paradoxus" By 

 ALEX. HILL, M.D. Received June 16, 1892. 



(Abstract.) 



The brain of Ornithorhynchus paradoxus is by no means Avian in 

 type. All its characters are Mammalian, but it presents certain 

 peculiar features which have been overlooked or misunderstood by 

 the anatomists who have hitherto examined it with the naked eye. 

 The most obvious and noteworthy departures from the form of brain 



M 2 



