Scientific Proceedings. 



29 



Distinctly alkaline; specific gravity, 1.02 1; depression of the 

 freezing point, 1.38 3 0 C. (mean of three examinations with differ- 

 ent portions of the fluid, 1.395 0 C, 1 .385 0 C, and 1.370 0 C, re- 

 spectively); electrical conductivity, 0.0091 19; chlorin calculated as 

 NaCl, 0.58 fo ; total nitrogen, 0.84 fo ; nitrogen from washed tan- 

 nic acid precipitate, expressed in percentage of the fluid, 0.83 fo ; 

 proteid (N x 6.25), 5.21 fo of the fluid; traces of reducing sub- 

 stance (sugar ?) after removing proteids with ferric acetate ; traces 

 of nitrogen liberated by hypobromite of soda ; no extractives of 

 appreciable amount upon shaking with ether, acetic ether, or chlor- 

 oform. 



The matter of chief interest in the results was the considerable 

 depression of the freezing point — 0.8 1 0 C. greater than that by the 

 blood, which was found to be 0.57 0 C. This 0.8 1° C. represents 

 nearly 0.438 gram-molecule in solution in excess of the molecu- 

 lar concentration of the blood, and appears to be a clear indication 

 that osmotic interchanges between this fluid and the blood did not 

 freely take place, possibly because of a thick layer of fibrin upon 

 the pleural surfaces. Such a deposit would not, however, explain 

 the high molecular concentration of the fluid. It appears most 

 probable that this was produced subsequent to the formation of 

 the fluid, by cleavages in the larger molecules originally present 

 in solution, or by the solution of substances not at first dissolved. 

 These substances could not be dissociable, because the electrical 

 conductivity was rather lower than is usual in such fluids. If the 

 substances causing the high molecular concentration were organic 

 compounds, they were not extractives soluble in ether, acetic 

 ether or chloroform. 



On the assumption that cleavage products of proteid substances, 

 precipitable with tannic acid, might be present and cause the un- 

 usual depression of the freezing-point, the following experiments 

 were made : Sterile horse serum, which had not been subjected to 

 heat, was divided into portions. Of these some were kept for 

 controls and others were inoculated with pure cultures of Staphyl- 

 ococcus pyogenes aureus or Fraenkel's pneumococcus. Freezing- 

 point determinations were made on certain of these portions and 

 the rest were sealed up in pipettes holding 100 c.c. each. These 

 were incubated at 37 0 C. for a week, when freezing-point determin- 



