GLAND TISSUE. 



129 



In modern times, however, the so advanced microscopic 

 analysis has furnished characteristics which, in our opinion, 

 permit of the certain recognition of a gland. 



Each of our organs (Fig. 117) consists of 

 two elements: 1st, of an, as a rule, hyaline 

 and thin membrane, the so-called gland 

 membrane, membrana propria id) ; and 2d, 

 of cellular contents (b) enclosed within the 

 latter. 



Without a blood supply, however, secretion 

 does not take place. A non-vascular gland 

 would be a nonentity. We therefore meet 

 with a vascular net-work (c), circumvoluting 

 the membrana propria, as a third integral 

 constituent. 



As further constituents, we have lymphatic 

 vessels, muscular elements and nerves. 



Let us now pass to the individual analysis. 



The gland membrane appears, at the first 

 examination, homogeneous, and, as a rule, 

 very delicate. Exceptionally, however, it 

 may acquire a thickness of 0. 001 to 0.002 mm. 

 It may also be replaced by undeveloped con- 

 nective tissue (sebaceous glands of the 

 skin). Finally, ordinary connective tis- 

 sue or a muscular layer may form a re- 

 inforcing stratum around this limiting 

 membrane. 



In more recent times, a manifold sys- 

 tem of quite flat stellate cells (Fig. 118) 

 has been met with which, embedded in 

 or resting on the homogeneous mem- 

 brana propria, form rib-like thickenings 

 of the latter, as for example, in the sub- 

 maxillary and lachrymal glands. 



Firm, extensible, and formed of a very unchangeable mate- 

 rial, probably related to the elastic substance, the membrana 

 6* 



Fig. 117. — A mam- 

 malian I.ieberkiihniun 

 gland ; <?, membrana 

 propria ; /', cells : r 

 capillaries ; d, gland 

 aperture. 



Fig. 118. — Plexus of star- 

 shaped, flat, connective-tissue 

 cells, from the membrana pro- 

 pria, isolated by maceration. 

 From the submaxillary gland 

 of the dog. 



