THE FEMALE REPRODUCTIVE ORGANS. 997 



amount, but after the sixth month begins to increase with some 

 rapidity. The fat-forming tissues are in full activity, therefore, 

 before birth, and function doubtless in the same way as in 

 the adult. Before birth also the various organs begin to take on 

 their normal activity. The kidney may form urine long before 

 birth, as is shown by the presence of this secretion in the bladder, 

 and, shortly before birth at least, it has the power of producing 

 hippuric acid, as may be shown by injecting benzoates into the 

 blood of the mother. The kidney functions of the embryo, how- 

 ever, are doubtless performed chiefly by the placenta and the 

 kidney of the mother up to the time of birth. That the liver also 

 begins to assume its functions early is shown by the fact that from 

 the fifth to the sixth month one may find bile in the gall-bladder. 

 In the intestine, colon, there is found also a collection of excrement, 

 the meconium, which shows that the motor and secretory functions 

 of the intestinal canal may be present in the last months of fetal 

 life. From the pancreas a proteolytic enzyme may be extracted at 

 the time of birth or before, but the amylolytic enzyme is not formed 

 apparently until some time later. It is stated, at least, that it is 

 not present at birth. In general, it is evident that for a long period 

 the maternal organism digests and prepares the food for the embryOj 

 excretes the wastes, regulates the conditions of temperature, etc., 

 as it does for a portion of its own substance, but as the fetus ap- 

 proaches term its tissues and organs begin to assume more of an 

 independent activity, as indeed must be the case in preparation 

 for the sudden change at birth. In this respect, as in all parts of 

 the reproductive process, we meet with regulations whose mechanism 

 is but dimly understood. 



Changes in the Maternal Organism during Pregnancy. 

 The two most distinct effects upon the mother that result from 

 pregnancy are the growth of the uterus and of the mammary gland. 

 The virgin uterus is small and firm, weighing from 30 to 40 gms., 

 while at the end of pregnancy it may weigh as much as 1000 gms. 

 This great increase in material is due partly to the growth of new 

 muscular tissue and partly to an hypertrophy of the muscle already 

 present. In the uterus at term the muscle cells are much longer 

 and larger than in the organ before the implantation of the 

 fertilized ovum. The stimulus that initiates and controls this 

 new growth is seemingly the fertilized ovum itself, but the phys- 

 iological means employed are not comprehended. We know 

 from experiments upon lower animals (Rein) that when all 

 connections with the central nervous system are severed the 

 fetus develops normally and the uterus increases correspond- 

 ingly in size and weight. The influence of the ovum on the 

 uterus must be exerted, therefore, in all probability, through 

 some chemical stimulus which it gives to the organ. The effect 



