HISTOLOGY OF THS OVIDUCT 01^ THf) DOMESTIC HE^N, 417 



to the great development of the tubular glands. These glands 

 are formed by invagination from the epithelium. Each gland 

 is a long, convoluted and branched tubule which opens to the 

 lumen of the oviduct by means of a short duct. The cells of 

 these tubular glands are characterized by small very dark stain- 

 ing nuclei which lie close to the basal walls of the cells. The 

 protoplasm is very granular especially before secretion. After 

 being emptied of its secretion, the cell has a more alveolar 

 appearance. 



The epithelium consists of two kinds of cells; (a) Ciliated 

 cells and alternating with these (b) unicellular glands. Differ- 

 ence in the appearance and staining reactions indicate that these 

 unicellular glands secrete a different substance from that pro- 

 duced by the cells of the tubular glands. 



Histology oF' the; Isthmus. 



As stated on page 400 there is a very sharp line of demarca- 

 tion between the albumen region and the isthmus. Towards the 

 posterior end of the albumen region the longitudinal ridges 

 become much lower. (Fig. 455)- On the isthmus side the 

 ridges are also quite low for two or three centimeters. After 

 that the ridges in the isthmus gradually become higher although 

 they never reach the height or breadth found in the albumen 

 portion. The real division between these parts of the oviduct 

 is a narrow line extending entirely around the duct. It is 

 plainly visible in the fresh oviduct as a line of translucent tis- 

 sue. (Fig. 455.) 



If we cut sections in such a way as to go through this division 

 line, we find the reason for its appearance. Figure 469, repre- 

 sents such a section. The albumen region is represented at the 

 left of the figure and the isthmus at the right. It is seen at 

 once that between these two regions the tubular glands are 

 either entirely or partially lacking. It is this feature which 

 causes the appearance of the line on the oviduct. The large 

 mass of tubular glands in the ridges is replaced by connective 

 tissue. The epithelium presents the same appearance as in the 

 albumen portion. Both the ciliated cells and the epithelial 

 glands are present. 



It should be said that the section represented in figure 469 is 

 cut very obliquely to the long axis of the oviduct. It thus hap- 



