454 Influence of High Pressures on the Circulation. [May 22, 



the same size as those used in Experiments 10 and 12, was injected 

 under the skin of the back with 4 minims of fresh serum of one of the 

 specimens of Tropidonotus used in those experiments. No effects 

 whatever were produced, though the animal was closely watched for a 

 time and kept under observation until the next day. 

 Experiments 12 and 13 were subsequently confirmed. 



Remarks on Experiments 8, 10, and 11. 



The parotid extract of the Aglyphous snakes used was a viscid 

 mucus, quite different from the thin opalescent fluid obtained from the 

 Opisthoglyphous snakes. Its chemical nature would also seem to be 

 different, the effects being much less like those produced by minimum 

 doses of Cobra venom. 



The violent general convulsions that followed the administration of 

 Zamenis extract seem to point to some direct effect upon the nervous 

 system, and are in marked contrast with the dyspnceic convulsions 

 that characterise poisoning by the Opisthoglyphous snakes used in the 

 first series of experiments. 



"The Influence of High Pressures of Oxygen on the Circulation 

 of the Blood." By Leonard Hill, M.B., F.E.S., and J. J. K. 

 Macleod, M.B., Mackinnon Kesearch Scholar of the Eoyal 

 Society. Eeceived May 22,— Eead June 12, 1902. 



In a former communication* one of us recorded the effect of a pres- 

 sure of two to three atmospheres on the circulation. 



We have since carried on the observations at much higher pressures 

 and by a different method. 



A tubular steel pressure chamber was constructed. The ends of the 

 tube were closed by thick glass discs. 



A curarised frog was placed inside, and the web of one foot stretched 

 on a wire ring just behind one of the glass discs. The pressure cham- 

 ber was placed in front of an arc light, and the web illuminated so that 

 the capillary circulation could be observed through a microscope (1-inch 

 objective). The pressure was rapidly raised to 70 atmospheres by 

 connecting the chamber with an oxygen cylinder. 



The capillary circulation continued. No alteration could be de- 

 tected during the rise of pressure. After 15-20 minutes the oxygen 

 tap was closed and the pressure chamber rapidly decompressed. For 

 the first half-minute there occurred no change in the circulation. Then 

 * ' Boy. Soc. Proc.,' 1900. 



