48 (2 18) Society for Experimental Biology and Medicine. 



the amount of blood in the general circulation is nearer the normal. 

 It is quite true, as Jurgensen supposed and as Gerhart also believed, 

 that the impulse from the left ventricle is directly felt by the right 

 — even the pulsation of the left ventricle communicated through 

 the imperfect valve to the left auricle is transmitted unchanged to 

 the pulmonary arteries, just as the pulsation of the right ventricle 

 is transmitted unchanged to the pulmonary veins. Since the right 

 ventricle contracts simultaneously with the left this direct beat of 

 the two ventricles against each other does probably account in 

 part for the hypertrophy of the weaker right ventricle. It may be 

 shown to occur by inserting a cannula into the cut end of the 

 pulmonary artery toward the lung so as to receive the blood 

 through the lung where it is found that on the production of mitral 

 insufficiency the pressure in that manometer rises and the curve 

 shows high pulsations synchronous with those of the ventricle. 



Mitral stenosis was produced by means of a clamp or by a 

 coarse suture passed through the heart and about the mitral ring. 

 The pressure is seen to rise very high in the pulmonary circula- 

 tion but because of the smaller amount of blood left to circulate 

 there it is lowered throughout the systemic circulation. 



26 (118). "Paramecium aurelia and mutation": GARY N. 

 CALKINS. 



The ordinary species is Paramecium caudatutn ; superficially, 

 it resembles P. aurelia. The latter differs from the former in 

 smaller size, in rounded instead of attenuated posterior end, and 

 in the possession of two instead of one micronucleus. The last is 

 generally regarded as the most important difference between the 

 two species. In March, 1905, a pair of conjugating Paramecium 

 can datum was isolated from a culture in an epidemic of conjuga- 

 tions. The ex-conjugates had all of the characteristics of P. 

 aurelia. One died before many generations in culture, the other 

 is still living and is now in the 346th generation. This one re- 

 tained the characteristics of P. aurelia until about the 45th gener- 

 ation after conjugation, when it lapsed again into the P. caudatum 

 form, with one micronucleus, and other characteristics of P. cau- 

 datum. The latter characters are still maintained. 



The observation indicates one of two things. Either this is an 



