332 E. R. HOSKINS 



ules arranged in rows. At the center of the gland the con- 

 nective tissue pushes the wall of the lumen into villous-like 

 processes covered with 'calciforme' epithelium which also de- 

 scends a short distance into the tubules. 



Sanfelice ('89) noted smooth muscle in the capsule of the digiti- 

 form gland. He described the epithelium of the central lumen 

 and of the ducts (tubules) emptying into it as stratified squa- 

 mous and that of the tubules (parenchyma) as glandular. He 

 noted goblet cells in the wall of the main central lumen and ex- 

 cretory ducts. 



Crawford ('99) divided the digitiform gland histologically into 

 three layers, namely, an outer fibro-muscular layer covered with 

 peritoneum, a middle glandular layer, and an inner region of 

 ducts and blood vessels surrounding a central lumen. The 

 outer layer consists of connective tissue and smooth muscle, 

 both circular and longitudinal, and contains large sinuses. 

 The glandular tissue is composed of tubules lined with granu- 

 lar, cubical, zymogen-free epithelium. In the inner layer the 

 ducts and the irregular central lumen are lined by transitional 

 epithelium, which is composed of several layers of polygonal 

 cells flattened at the free surface. The outer layer is often 

 degenerated. Among the ducts are large sinuses. The cells 

 in the 'acini' (peripheral), judged from their resemblance to 

 renal epithelium, may be excretory. The vascular system con- 

 sists of central and peripheral sinuses joined by capillaries. 



Sullivan ('07) noted that the surface cells lining the main 

 central lumen undergo mucoid changes and that clear cells may 

 be seen lining the ducts. 



Pixell ('08) added that the tubules may turn at their periph- 

 eral ends and extend longitudinally, and that goblet cells 

 are present in the tubules. She states that the digitiform gland 

 resembles in structure the compound pyloric appendage of Aci- 

 penser and Lepidosteus. 



Hyrtl ('58) termed the artery from the aorta supplying the 

 digitiform gland the posterior mesenteric. Parker ('87) called 

 this artery the 'spermaticomesenteric posterior.' Hochstetter 

 ('88) pictured the digitiform gland as though its vein enters 



