SALIVA. 383 



55 -6 volumes of carbonic acid, 

 9 '6 volumes of oxygen, 

 6 '4 volumes of azote. 



3. Blood of birds. Prevost and Dumas found the blood from 

 the jugular vein of the following birds composed of, 



Clot. Serum. Water. 



A young raven, 14-66 5-64 . 79-70 



A heron, , 13-26 . 5-92 . 80-82 



A duck, . 15-01 . 8-47 . 76-52 



A hen, ?i.r 15-71 . 6-30 . 77-99 

 A pigeon. . 15-57 . 4-69 . 79-74 



The facts just stated, few and imperfect as they are, show clear- 

 ly that the constitution of the blood is different in different ani- 

 mals. 



CHAPTER II. 



OF SALIVA. 



THE saliva is a liquid secreted by six glands, three on each 

 side of the mouth. These are the two parotids, the two submaxil- 

 lary, and the two sublingual. 



It is a liquid, which is colourless or nearly so. It is not quite 

 transparent, containing a few white flocks, which gradually sink 

 to the bottom, when the saliva is collected in a glass. Probably 

 these flocks come from the mucus which lines the ductus stenoni- 

 anus and the other salivary ducts. 



It is not easy to form a notion of the quantity of saliva secret- 

 ed by the salivary glands ; though it must be considerable. M. 

 C. G. Mitcherlich collected all the saliva from one of the paro- 

 tid glands of a patient in an hospital in Berlin, who had a fistu- 

 la in that parotid. In 24 hours it amounted to 1048 grains. 

 Hence in this case the two parotids must have secreted 2096 grains 

 in 24 hours. The submaxillary and sublingual glands are much 

 smaller than the parotids. But if we suppose them equal to one 

 parotid, the whole saliva secreted in 24 hours will be 3144 grains, 

 or almost 7J ounces avoirdupois.* 



* Poggendorf s Annalen, xxvii. 320. 



