44 SECRETION. 



The normal quantity of pericardial fluid in the human 

 subject is generally estimated at from one to two flui- 

 drachms. Colin found that the pericardial sac of the horse 

 contained from two and a half to three and a half fluid- 

 ounces, the cavity being exposed immediately after the death 

 of the animal from haemorrhage. 



The quantity of fluid found in the peritoneal cavity in 

 horses killed in this way was from ten to thirty-four fluid- 

 ounces. 



The quantity of fluid in the pleural cavity in the same 

 animal was from three and a half to seven fluidounces. 1 



These estimates are simply approximative ; but they give 

 an idea of the normal quantity of liquid which may reason- 

 ably be supposed to exist in the serous cavities of the 

 human subject. Judging from the weight of a man of 

 ordinary size as compared with that of a horse, it may be 

 stated, in general terms, that the pericardial sac contains 

 from two and a half to three and a half fluidrachms ; the 

 peritoneal cavity from one to four fluidounces ; and the 

 pleural sac from three and a half to seven fluidrachms. 



The fluid in the cavity of the tunica vaginalis is small in 

 quantity, and resembles in every respect the peritoneal secre- 

 tion. The cephalo-rachidian, or subarachnoid fluid will 

 be described in connection with the anatomy of the cerebro- 

 spinal nervous system. 



Synovial Fluid. Although there is a certain similarity 

 between the serous and the synovial membranes, their secre- 

 tions differ very considerably in their physical and chemical 

 characters. Like the serosities, the synovial fluid has simply 

 a mechanical function ; but it is more viscid, and contains a 

 larger proportion of organic matter than the serous fluids. 

 The quantity of fluid in the joints is sufficient to lubricate 



has collected the latest analyses of the pleural fluid, the pericardial fluid, the 

 fluid of ascites, and the fluid of hydrocele. 

 1 COLIN, loc. cit. 



