700 REPRODUCTION AND GROWTH 



D. INNERVATION OF THE SEXUAL ORGANS 



Experimental data on the innervation of the uterus differ widely. While 

 some authors state that the circular muscle fibers are innervated by the nervi 

 erigentes and the longitudinal fibers by the hypogastric, Langley and Ander- 

 son have reached the conclusion that (in the rabbit and cat) only the lumbar 

 nerves convey motor fibers and that these supply both the longitudinal and 

 circular musculatures. The effect of unilateral stimulation is felt chiefly on 

 the same side. 



Nagel describes the innervation of the uterus in the woman as follows: one 

 trunk arises from the hypogastric plexus, while others arise from the sacral 

 nerves. The former receives fibers from the third sacral and sends a branch to 

 the ureter. It then betakes itself to the cervical ganglion (plexus utero-vagi- 

 nalis) which lies in the neighborhood of the lateral vaginal fold. 



Besides this ganglion, -which receives branches from the fourth sacral and 

 is also connected with the hemorrhoidalis nerve, there are found in the vicinity 

 of the ureter two other ganglia (the vesical plexus) : the three ganglia are 

 connected with one another and send branches to the uterus, the vagina, etc. 

 Most of the uterine nerves come from these ganglia; a smaller part of them 

 pass directly from the hypogastric plexus. 



The nerves of -the ovaries arise from the plexus renalis and from the lower 

 portion of the plexus aorticus abdominalis. 



The plexus surrounding the vagina arises from the cervical and vesicular 

 ganglia, but also receives twigs from the third and fourth sacral nerves. 



Movements of the uterus can be produced by stimulation of the different 

 parts of the central nervous system (lumbar cord, medulla oblongata, anterior 

 part of the optic thalami, cerebral cortex, probably the motor zone). But the 

 uterus contracts spontaneously at a certain rhythm even when it is cut out 

 of the body, and birth has been known to take place in a perfectly normal 

 manner with all the uterine nerves cut (Rein) and after entire extirpation 

 of the lower end of the spinal cord (Goltz and Ewald, cf. page 583). The 

 central nervous system therefore plays a relatively unimportant part in con- 

 trolling the movements of the uterus. 



According to Keilmann and Knupffer, parturition takes place at once if 

 the cervix be everted as far as the ganglion of the cervix. But Eein states 

 that (in the dog) parturition takes place also after extirpation of the ganglion. 



3. SECRETION OF MILK 



The newborn child is not far enough developed to seek and to take food 

 without help. Its digestive organs are not yet capable of modifying the 

 ordinary mixed diet of man, consequently nourishment for the child must 

 be prepared for some months in the body of the mother. This is accomplished 

 through the activity of the mammary glands which form and secrete the milk. 



A. MILK 



Milk constitutes the natural food of the child and hence contains in proper 

 relative proportions all the foodstuffs necessary for the maintenance and devel- 



