42 PROTOPLASM AND THE CELL 



reason to suppose that secondary sexual characteristics are 

 developed at maturity through the action of hormones secreted 

 by the reproductive glands into the blood. A close relation 

 exists also between the glandular patches known as the corpora 

 lutea on the mammalian ovary, fixation of the fertilized eggs to 

 the wall of the uterus, and stimulation of the mammary glands. 

 If these small glands on the ovary are removed, the developing 

 egg will not attach at all, and it is supposed that a hormone is 

 secreted which reaches the uterus through the blood and causes 

 the cells of the uterus to react to the embryo. Again the 

 pituitary body in the brain plays an important part in regulat- 

 ing growth of the organism, diseases of this gland giving rise to 

 acromegaly, one of the symptoms of which is the excessive de- 

 velopment of parts of the organism far removed from the brain. 

 Vita/mines. Still another group of elusive chemical bodies are 

 the so-called vitamines, named by Casimir Funk. Like enzymes 

 and hormones, these are substances of unknown chemical com- 

 position which appear to be necessary for the proper nourish- 

 ment of the body. They are undoubtedly organic in nature but 

 are neither proteins, carbohydrates, nor fats. They may be 

 extracted from these normal foods by alcohol, and are destroyed 

 by heat and by alkalies. They contain nitrogen, but no phos- 

 phorus, and are probably reducing substances. Vitamines are 

 best known in connection with the disease known as Beri-beri 

 which is caused by eating white polished rice as a sole or staple 

 article of diet. While such rice contains abundant nourishment, 

 the body cannot utilize this nourishment without the aid of 

 vitamines which should go with the rice. The outer coatings of 

 the rice kernels, which are removed in the preparation of white 

 or polished rice, contain such vitamines, and if these husks are 

 eaten with the rice, a proper nourishment results. Scurvy 

 is another disease which apparently results from the absence 

 of vitamines. All normal foods, whether proteins, carbohy- 

 drates, or fats, contain these essential substances but in dif- 

 ferent degrees, and all such food substances can be rendered 

 innutritious by previously extracting the vitamines while, on 

 the other hand, excellent results in growth and increase in weight 



