THE THYKOID GLAND 



559 



broken into minute spherules. In general, the' ratio of colloid content 

 within the follicle, roughly stated, is in proportion to the age of the in- 

 dividual. The follicles at the periphery of the lobes of the gland are 

 less fully distended than those in the in 



Embedded in the colloid mass withir 



ently normal thyroid, red blood corpuscles and desquamated follicular 



epithelium are frequently found, but m 

 cytes are of less frequent occurrence an 



erior. 



.the follicle, even in the appar- 



ver in large quantity. Leuko- 

 are more rarely found in the 



human thyroid than in that of the lower\mammals. 



The FOLLICULAR EPITHELIUM is typically cuboidal in shape; in 

 young individuals it is somewhat taller than broad. In those follicles 

 which are distended with colloid secretion the epithelium is relatively 

 short ; in those which are empty it is tallep. Each cell contains a single 

 spheroidal nucleus which lies in the center of the cell, or somewhat 

 toward its basal extremity. This orderly! disposition causes the nuclei, 

 when seen in sections of the follicle, to appear as a continuous row in 

 the wall of the alveolus, a disposition wjiich is noticeable for its ex- 

 ceptional regularity. 



The cytoplasm of the epithelium is 

 acidophilic. It usually contains some 

 fatty droplets, which generally occupy the 

 nute spheroidal granules which give the 

 also found in the cytoplasm of the epithelial cells. Hiirthle (Arch. f. d. 

 ges. PhysioL, 1894), by staining with the Biondi-Ehrlich mixture, suc- 

 ceeded in differentiating two types of cell, one lightly staining, the 

 'chief cells/ the other a darker colloid-containing type which he designated 

 as 'colloid cells/ These variations probalbly only represent different 

 stages of secretion in the same epithelial cell type. Minute intercellular 

 canaliculi occur at the angles between adjacent cells. 



In the thyroid of the opossum Bensley (Anat. Rec., 8, 9, 1914) also 

 describes two types of cells, namely, the usual epithelial cells and ovoid 

 cells. The latter hold -a parietal position ip. the follicle; they are filled 

 with fine eosinophilic granules which give t6 these cells a character strik- 



iely granular and decidedly 

 ?e granules and very small 

 [tremities of the cells. Mi- 

 >lor reactions of colloid are 



ingly similar to that of the acidophil cells o 

 physis cerebri. He describes also large nee< 

 the epithelial cells similar to those in the 

 the testis. 



' the anterior lobe of the hypo- 

 ile-shaped crystalloid bodies in 

 aterstitial and Sertoli cells of 



v 



The epithelium rests upon a very delicate reticular basement mem- 

 brane and is inTcIose. Delation with the capillaries and lymphatic vessels. 



