SEROUS SECRETIONS. 4:3 



tion, only enough fluid is secreted to keep these surfaces in 

 a proper condition. The error frequently committed by 

 authors, in describing the serous exhalations as vaporous, 

 is due to the fact that a vapor is generally given off when 

 the serous cavities are exposed, either in a living animal or 

 in one recently killed. This vaporous exhalation takes place 

 after exposure of the parts ; but if the cavities be observed 

 without exposing the serous surfaces to the air, a certain 

 quantity of liquid can be detected. Colin always found 

 liquid in the peritoneal, pericardial, and pleural cavities of 

 animals recently killed or opened during life. In these 

 cavities the opposite surfaces of the serous membrane were 

 either in contact, or the space between them was filled with 

 liquid. In one of the small ruminants, he removed the 

 muscles and the elastic tunic from the lower part of the 

 abdomen, exposing the transparent peritoneum, and through 

 this membrane could see liquid collected in the dependent 

 parts. 1 



As far as has been ascertained, the secretions of the dif- 

 ferent serous membranes bear a close resemblance to each 

 other. They are either colorless, or of a slight amber tinge, 

 alkaline in reaction, and have a specific gravity of from 

 1012 to 1020. Their composition resembles that of the 

 serum of the blood, except that the proportion of water is 

 very much greater. They contain albumen, chlorides, car- 

 bonate and phosphate of soda, and a little glucose. These 

 facts are the result of observations upon the serous fluids of 

 some of the inferior animals ; 3 and it is exceedingly difficult 

 to obtain the normal fluids from the human subject. The 

 elaborate analyses which are sometimes given of the fluids 

 from the different serous cavities in the human subject are 

 the results of examinations of large morbid accumulations. 8 



1 COLIN, Traite de physiologic comparee dts animaux domestiqucs, Paris, 1856, 

 tome ii., p. 438. 

 3 COLIN, loc. cit. 

 * ROBIN, Lemons sur les humeurs, Paris, 1867, p. 262, et seq. This author 



