OF THE GLANDS. 319 



proportion as it divides in more minute ramifications in the 

 glands. This membrane is invested externally by cellular 

 tissue, and by an elastic tissue; in some ducts by an erectile 

 one, as in the urethra, in the nipple, and perhaps in some 

 others; in some parts of the excretory passages, the mucous 

 membrane contains muscular fibres. 



487. The intimate texture of the glands is little known. 

 Malpighi had advanced that each of the glandular grains, the 

 acini, ought to be considered as a follicle, and each gland as a 

 conglomeration of follicles, terminating in a common excretory 

 canal. This opinion was received and admitted without being 

 contradicted until Ruysch, and in his times defended against 

 him by Boerhaave. According to Ruysch, on the contrary, 

 the parts which have been called glandular grains, consisted 

 solely of minute intertwined vessels, in which the arteries 

 should continue and terminate in excretory canals. 



In each of these two opinions there are some things true that 

 we must admit, and some parts inexact, that we mustr eject. 

 It is true, as stated by Malpighi, that a gland consists, like a 

 simple or compound follicle, of a canal closed at the extremi- 

 ty; it is true also, as it is affirmed by Ruysch, that each glandu- 

 lar grain, and that the entire gland consists of a mixture and 

 intertwining of minute vessels with the origins of the excre- 

 tory ducts; but it is as incorrect to say, as he has stated, that 

 the excretory ducts are the continuation of the arteries, as it 

 would be inexact to say with Malpighi, that the radicles of 

 the excretory ducts commence by enlargements or follicles. 

 Perhaps the hypothesis of Malpighi would be more probable 

 if confined to the granulated glands, as the salivary, the pan- 

 creas and lachrymal glands, which, in fact, so much resemble 

 compound follicles; and that of Ruysch would more likely be 

 true by applying it only to the liver, the kidneys and testicles, 

 the texture of which is so evidently vascular and canaliculated, 

 without, however, being able to affirm that true hollow follicles 

 exist in the first mentioned organs, and in the others direct 

 continuations between the arteries and the excretory ducts. 



In support of this conjecture might be adduced the facility 

 with which, in the latter glands, injections pass from the ves- 

 42 



