42 



SCIENCE 



[N. S. Vol. XLVI. No. 1176 



as shown hy the test. Pragmatism may be 

 vicious wlien narrowly conceived, but the prag- 

 matic attitude leads us away from dogmatic 

 idealism toward intelligent action. The Ger- 

 man army, in its conduct toward its own mem- 

 bers as well as its treatment of the unfortunate 

 peoples who come under its power, does indeed 

 strive for " values " independently of pleasure 

 or pain. Nationalistic idealism can be made 

 the excuse for deeds which could find no justi- 

 fication in the presence of the simplest en- 

 quiries into consequences, as measured by 

 those supposedly negligible phenomena, human 

 pleasure and pain. Miinsterberg, great-hearted 

 and striving after good, would not have so far 

 forgotten the relations between cause and ef- 

 fect; but we must combat any philosophy, any 

 course of action, which does not incessantly 

 seek justification by results measured in hu- 

 man welfare. 



T. D. A. COCKERELL 



SPECIAL ARTICLES 



A RHYTHMICAL " HEAT PERIOD " IN THE 

 GUINEA-PIG 



During the past, six years we have been using 

 guinea-pigs in an extensive breeding experi- 

 ment and it has become more and more evi- 

 dent as our work goes on that the existing no- 

 tions of the ovulation periods in these ani- 

 mals are of no practical value, or are prac- 

 tically incorrect. In a number of the experi- 

 ments it became important to know accurately 

 when the females " came into heat " and when 

 ovulation took place. We had concluded, from 

 numerous observations as well as theoretically, 

 that the female guinea-pig very probably had 

 a definitely regular and periodic sexual cycle 

 if it could be worked out exactly. On account 

 of the need of this exact information, we have 

 studied the CBstrous cycle in these animals dur- 

 ing the past eighteen months. 



Most other attempts at a solution of this 

 problem have centered in a study of the ovary, 

 which necessitated either its removal by oper- 

 ation or the killing of the animal. In either 

 case the procedure brought to a conclusion the 

 observation or experiments on the ovulation 

 cycles in that specimen. Recognizing, on the 



other hand, that no thorough investigation of 

 the uterus and vagina in the living female had 

 been made, it occurred to us that possibly 

 oestrous changes might take place even though 

 they are so feebly expressed as not to be notice- 

 able on casual observation. The absence of an 

 apparent oestrous or procestrous fiow from the 

 vagina of the guinea-pig has, no doubt, been 

 the chief reason for the general lack of knowl- 

 edge of the oestrous cycle. It was, therefore, 

 determined to make a minute examination of 

 the contents of the vagin® of a number of fe- 

 males every day for a long period of time to 

 ascertain whether a feeble flow might exist, al- 

 though insufficient in quantity to be noticed 

 at the vaginal orifice or vulva. 



The observations were made by using a small 

 nasal speculum which was introduced into the 

 vagina and the arins opened apart by means 

 of the thumb screw. This instrument permits 

 an examination of the entire surface of the 

 vaginal canal. In this way the vaginae of a 

 number of virgin females have been examined 

 daily and smears made from the substances 

 that happened to be present in the lumen. 



By the use of such a simple method, it was 

 readily determined after examining the first 

 lot of animals for a few months that a definite 

 sexual period occurs lasting for about twenty- 

 four hours and returning with a striking reg- 

 ularity every fifteen or sixteen days. During 

 this twenty-four hour period the vagina con- 

 tains an abundant fluid which is for about the 

 first half of the time of a mucous consistency. 

 The vaginal fiuid then changes into a thick 

 and cheese-like substance which finally be- 

 comes slowly liquefied and serous. This thin 

 fluid exists for a few hours and then disap- 

 pears. Occasionally toward the end of the 

 process a slight trace of blood may be present, 

 giving the fluid a bloody red appearance, other- 

 wise it is milk-white or cream color. 



According to the changes in appearance and 

 consistency of the vaginal fluid, one may dis- 

 tinguish four different stages. The first stage 

 having a mucous secretion, a second stage the 

 cheese-like secretion, a third stage with the 

 fluid becoming serous and a fourth stage, not 

 always recognized, during which a bloody dis- 



