542 



Capt. J. Hammond. 



Watson* has also shown that the corpora lutea of the rat during the 

 lactation period are very large and bigger than corpora lutea spuria. He 

 was inclined to' believe that they were corpora lutea of pregnancy, which 

 had not degenerated in the latter part of gestation. 



In order to test this supposition, the corpora lutea of a series of rabbits 

 in various conditions as regards sexual activity (pregnant, pseudo -pregnant, 

 with decidual tissue produced, and with foetuses removed) were measured 

 as a test of their state of development. The method has been to cut free- 

 hand sections of the corpora lutea in the ovaries, which in almost every case 

 had been preserved in formalin. Three or four sections showing the 

 greatest diameter from each corpus luteum were picked out. Their 

 diameter was accurately measured under the low power of the microscope 

 by means of a scale attached to the mechanical stage. In every case the 

 largest diameter was measured. As a rule three or four corpora lutea from 

 the ovaries of each rabbit have been measured in this way, and the results 

 arranged so that each figure given in the Table (I) below represents the 

 average of about sixteen measurements. 



The figures given are no doubt influenced to some extent by the size and 

 age of the rabbit, but, nevertheless, they show quite clearly that the corpus 

 luteum of pregnancy undergoes a further development than that of the 

 pseudo-pregnant condition. 



The latter portion of the Table shows that this further development of the 

 corpus luteum is not correlated either with the growth of the maternal 

 placenta (as shown by the animals in which this condition was experiment- 

 ally produced), or with the formation of the foetal placenta or membranes (as 

 shown by the removal experiments). 



In order to correlate with these observations the effect of the same 

 treatment on the mammary gland, a similar Table has been made out for 

 this gland. The pseudo-pregnant growth of the gland is mostly in the 

 lateral direction, so that in stained and cleared specimens one can easily see 

 the changes occurring ; but in the second stage of development the growth is 

 rather in thickness, so that other means have to be taken to demonstrate its 

 growth during this period. 



The mammary glands have been dissected out, attached to their usual 

 muscular band, and fixed in alcohol. The four centre glands, with the 

 muscle beneath them, have then been cut out and weighed. This is not such 

 a satisfactory mode of measurement as that used for the corpus luteum, for it 

 is more dependent on the size of the animal and the amount of muscle taken 

 with the gland. It is sufficiently accurate, however, to show that the degree 

 * Watson, ' Proc. Phys. Soc.,' 'Journ. of Physiol.,' vol. 34 (1906). 



