AUTHORS ABSTRACT OF THIS PAPER ISSUED 

 UY THE BIBLIOGRAPHIC SERVICE AUOUST 18. 



THE EXISTENCE OF A TYPICAL OESTROUS CYCLE 

 IN THE GUINEA-PIG— WITH A STUDY OF ITS HIS- 

 TOLOGICAL AND PHYSIOLOGICAL CHANGES 



C'lT.VKLES R. S'r(^CKARD AND GEORGE N. PAPANICOLAOU 



Dcpaiitiicnl of Aiidlniin/, ('unicll V iiivcr^llji Mcilicdl School, A^eir )'ork Clly 



ONE TKXT FKailtR AND NINE I'LATRW 



1. INTRODUCTION 



The existence of a more or less regular and definite oestrous 

 cycle has been recognized in a number of mammals, particularly 

 among the different classes of primates, carnivores, ungulates 

 and insectivores. Yet very little is actually known or under- 

 stood regarding the oestrous cycles and heat periods of a great 

 many other very common mammals. Strangely enough, our 

 knowledge of the sexual rhythm in the guinea-pig is much con- 

 fused and not properly understood despite the great number of 

 breeding experiments and the several studies of the sexual con- 

 ditions which have been performed on this animal. 



While conducting an extensive breeding experiment with 

 guinea-pigs for the past several years it has become more and 

 more desirable to know their exact oestrous periods. ^ A care- 

 ful study of the existing literature bearing on this subject serves 

 merely to produce uncertainty and confusion regarding their 



1 Throughout this paper we have used the terminology proposed by Heapc, 

 Quar. Jour. JMic. Sc, vol. 44, 1900, and adopted by Marshall and others. An- 

 oestrous period or anoestrum, period of rest in the female; prooestrum, the 

 first part of the sexual season; oestrus or oestrum, especial jx^rind of desire in 

 the female; metoestrum, the short period when the activKy of the ii;cn<Ma( ivc 

 system subsides and the normal condition is resumed in case concei)ti()n did not 

 occur; dioestrum, the short period of rest which in some mammals lasts only 

 a few days. Such a short cycle as we shall describe in tiie guinoa-i)ig consist in<i; 

 of four periods the prooestnnn, oestrum, metoestrum and dio(>struiii is known as 

 a (liocstrous cycle. 



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