THE GLANDS: THYROID AND PITUITARY 63 



is a collection of solid columns of cells, surrounded by blood 

 spaces into which their secretion is undoubtedly directly poured. 

 A gelatinous material, presumed to be the internal secretion of 

 the gland, has, in fact, been observed emerging from the cells 

 into the blood spaces. The posterior lobe, or gland, consists of 

 secreting cells producing a glassy substance which finds its way - "" 

 into the spinal fluid that bathes the nervous system. The spinal ^ 

 fluid itself is a secretion of another gland at the base of the brain, 

 the choroid. Nerves and internal secretion are associated here 

 with a closeness symbolic of their general relations. 



From each portion of the gland (to stick to the accepted nom- 

 enclature of speaking of the two glands as one) an active sub- 

 stance has been isolated. Robertson, an American chemist, 

 separated from the anterior lobe a substance soluble in the fat 

 solvents, like ether and gasoline, which he christened tethelin. 

 But P. E. Smith has shown that the active material is soluble 

 neither in boiling water nor in boiling alcohol, the typical 

 fat solvent. A number of facts favor the idea of the anterior"" 

 lobe cells as stimulants of growth of bone and connecting and_^ 

 supporting tissues generally. From the posterior lobe, pituitrin, 

 believed its internal secretion, has been obtained in solution. 



Pituitrin is a substance of many marvelous functions. In gen- 

 eral, it controls the tone of the tissues, of involuntary or smooth m 

 muscle fibres of the blood vessels and the contractile organs of 

 the body like the intestines, the bladder and uterus. When in- -m 

 jected, it will slowly raise the blood pressure and keep it raised 

 for some time, and will increase the flow of urine from the kid- 

 neys and of milk from the breasts. It will also cause an intense 

 continued contraction of the bladder and the uterus. It is also 

 said to control the salt content of the blood upon which its 

 electrical conductivity and other properties depend. Normally, 

 there is a certain fixed ratio of the salts in the blood, which keeps 

 them like the ratio in sea- water. Again, we have an example of 

 the curious atavism of the internal secretions. The thyroid, 

 remember, keeps the iodine concentration of the blood like that of 

 the ocean, our original habitat. Pituitrin likewise does its part 

 to maintain our internal environment as near as possible to what 

 was once the surrounding medium. A substance somewhat similar 

 has been found in the skin glands of toads. 



The extraordinarily well protected position of the pituitary, its 

 persistence throughout life, and its abundant blood supply, em- 

 phasize its vital importance. No other gland of internal secretion 



