Structure of the Tissue. 



9 



vessels and lymph vessels. Numerous and strong elastic fibres 

 strengthen the dense fibrillar connective tissue of the teats. 



In order to describe the finer structure of the parenchyma of 

 the udder it is necessary at first to touch on the further develop- 

 ment of the organ from birth until the moment of the appearance 

 of the secretion. 



(a) Normal Appearance. 



The milk gland is an organ which performs increased func- 

 tions only at certain times. It does not secrete during the entire 



Fig. 4. 



Vertical section through the lower end of the teat canal which is closed by a horny plug (a). 



life but only when the newly born offspring is to be nourished by 

 the milk. The udder of a virgin animal does not correspond even 

 in its finer structure, with the appearance of a fully secreting 

 udder, and this again varies in its finer structure from a gland 

 which is at the beginning or at the end of the lactation period ; even 

 this is not all, since the microscopical appearance changes in ac- 

 cordance with the condition of activity, where a lobule or only a 

 part of the lobule may be found on examination, depending 

 whether the cell-complex is just forming the secretion or has al- 

 ready discharged its secreted product. 



The gland of a newly born calf shows but relatively few cell tubes and cell buds, 

 imbedded in connective tissue rich in fat and branching in all directions. These prac- 

 tically form the basis of the glandular ducts and are without alveoli. The end of the 

 tubes is frequently somewhat dilated, or thickened in the form of a club. 



