Atkins — Osmotic Pressures of the Blood and Eggs of Birds. 127 



Ehea Americana, 0-662° 7-97 



Tlie osmotic pi-essures were calculated from tlie formula n =^ 12-06 A 



- 0-021 A=. 



It is noticeable that all the samples of blood examined froze between 



- 0-53°O. and - 0-66°O., with one exception, probably pathological, though 

 each class has a fairly constant freezing-point. 



In Gallus hankiva the variations are very small — -O'OSPC. between the 

 extremes, neglecting one remarkable value, A = 0-935° C. The latter was 

 repeated tln-ee times ; tlie blood was perfectly fresh. It was the only sample 

 received from a farm ; and no particulars as to Ijow it" was collected were 

 obtainable. It seems probable that it was got by killing a diseased bird. 



In Meleagris gallopavo a practically identical range was found, 0-035° C. ; 

 while in Anser also the range was 0035° 0. lu Anas tlie difference 

 between the extremes is 0-028° C, neglecting the results of the two de- 

 composing specimens. 



It is to be noted that the values of A for the fowl, A = 0-6'J7'O., aud 

 turkey, A = 0-621°O., are higher than those of the duck, A = 0-574''O., and 

 the goose, A = 0-552°O., both of wliioli ai'e aquatic. Hamburger states' that 

 the osmotic pressure of the blood of birds of prey is higher than that of other 

 birds, being isotomic with a solution of sodium chloride considerably above 

 1 per cent. He gives 0-698° 0. as the value of A obtained by him for a ] per 

 cent, solution of this salt. 



The value of A 0-662° C. given by the blood of the American ostrich, 

 Rhea, is the highest found for any bird.' It is impossible to draw definite 

 conclusions from one experiment, especially as the blood was obtained from a 

 bird which had died from cold. It was, however, in perfect condition, and 

 the blood was quite fresh ; and it is worthy of note that Rhea is a Ratite bird, 

 all the others being Oarinate. 



Turning now to the egg, it is found tiiat the mean value of A for the 

 egg of Gallus is identical with that for Anas, the difference 0-002° 0. being 

 quite negligible, while the value of A given by the blood of these two differs 



' Osmotischer Druoke und loneulehre, vol. i., p. 458. 



' I have to thank Dr. A. F. Dixon and the Royal Zoological Society of Ireland for this and 

 several ()tlier specimens. 



