Precipitin Response in Blood of Rabbits. 9 



diminished because of the diminution of hemoglobin. In spite 

 of the fact that the difference in carbon dioxid content and tension 

 between arterial and venous blood is comparatively small, there 

 is a very definite difference in P H . The arterial P H lies well to 

 the alkaline side of the 7.35 line in those cases where there is a 

 difference, while the venous point lies practically on the 7.35 line. 



It is suggested tentatively as an explanation of this phe- 

 nomenon, that the tissue CCVtension and P H must lie at or above 

 that of the venous blood and not in equilibrium with the arterial 

 blood. As it is presumably the tissue C0 2 - tension or hydrogen- 

 ion concentration in the respiratory center which controls the 

 respiratory mechanism, the tendency of the repsirations will 

 be to maintain this constant rather than the hydrogen-ion con- 

 centration of the arterial blood. In normal persons arterial 

 and venous P H are practically identical because of the slope of the 

 dissociation curve and the effect of oxygen. In anemia the 

 effect of these compensating reactions is diminished so that true 

 relations become more evident. It has already been demon- 

 strated by Michaelis, 1 and others that the hydrogen-ion concen- 

 tration of the venous blood is maintained constant at P H = 7.35 

 with a variation of ±0.08, which agrees well with our values for 

 both arterial and venous P H . 



4 (1586) 



Precipitin response in the blood of rabbits, following subarach- 

 noid injections of horse serum. 



By H. L. Alexander. 



[From the Second Medical Division of Bellevue Hospital, and the De- 

 partment of Medicine } Cornell University Medical College.] 



During the treatment of cases of cerebrospinal meningitis 

 with antimeningococcic serum in a large Army hospital, 2 a curious 

 reaction was repeatedly observed. This appeared in patients 

 who, after having received several intraspinous treatments 

 with serum, were given serum intravenously. While such injec- 



1 Michaelis, Wasserstoffionenkonzentration, Berlin, 1914. 



2 Hospital of the American Embarkation Center, LeMans, France. 



