THE THY Roll) (ILAM) 255 



substance within the folHcli', and i)at('iies of sciuanious ('])itheHuni 

 left over from embryonic buccal e])ithelium. 



The pars interme(na consists of epithehoid cells, some of which 

 are coluuuiar in type. Follicles nuiy occur. In some cases the cleft 

 between the i)ars intermedia and i)ars distalis has been obliterated, 

 so that it is very difficult to note any histoloi^ical difference between 

 the two reo;ions. 



The pars neuralis ai)])ears to possess cells which are more like 

 neurofjlia than neurons. Some are spindle-shaped and some stellate 

 with numerous processes. The fibers present are non-medullated. 

 The cavity of the original embryonic infundibular evagination 

 remains in the |)ituitary of the cat, but disappears in many other 

 animals. 



Although much positive information has been gathered concern- 

 ing the functions of the pituitary, further research is necessary 

 before it is completely understood. If the pars distalis is ex])eri- 

 mentally removed in young animals, they remain small in stature 

 and the skeleton does not grow^ Hyposecretion from this lobe 

 causes diminished oxygen metabolism, dry skin, decrease of hair 

 formation, short appendages, and dwarfism. Hypertrophy or hyper- 

 secretion in young individuals causes formation of more adipose 

 tissue, larger bones, and gigantism. If the anterior lobe hyper- 

 trophies in adults, the bones and soft parts of the face, hands, and 

 feet grow larger, a condition known as acromegaly. 



The pars neuralis apparently produces a secretion which tends 

 to cause a rise in blood-pressure, a modification in the \olume of 

 urine formed in a given time, and increased milk flow in acti\'e 

 mammary glands. It is somehow related to the change of glycogen 

 to glucose in the liver; it causes contraction of the smooth muscle 

 of the bladder, intestine, and uterus. Because of this last-named 

 property, extract of pars neuralis substance, or "pituitrin," is 

 employed in obstetrics. 



Removal of the entire pituitary from living animals results in a 

 lowering of basal metabolism, lowering of body temperature, and 

 in a short time even death. 



THE THYROID GLAND. 



In fishes this gland is a number of small follicular masses along 

 the ventral aorta. In the frog, two masses are separated, each 

 portion being located laterally in the floor of the mouth between 

 the posterior lateral and thyrohyoid ])rocesses of the hyoid appa- 



