LETTERS TO BROTHER JOHN. 41 



mentioned, prevent its regurgitation, or gravitation 

 backward. 



I have said, that there is scarcely any point in 

 the body which is not occupied by vessels and 

 nerves. It follows, therefore, that there is scarcely 

 any point of it which does not consist of vessels and 

 nerves; and this is true. When you look at a 

 piece of red raw flesh, that which appears to you a 

 solid mass is, in fact, little else than a wonderful 

 and compact tissue of nerves and hollow tubes, 

 firmly compressed and matted together. The only 

 solid parts are the nervous threads, a little cellular 

 substance, and the delicate membranes forming the 

 coats of those hollow tubes ; that is, the blood- 

 vessels and absorbents ; and even these are porous 

 at least the blood-vessels. Even that which 

 anatomists call the muscular fibre, and which you 

 call the grain of the meat, has been asserted, by 

 Ruysch, to be no more than little bundles of vessels 

 minute tubes, like the hairs of your head ; every 

 one of which you, of course, know is hollow. 

 Ruysch's opinion is very high authority; for he 

 possessed a secret which enabled him to carry the 

 art of injecting minute vessels to a degree of 

 nicety which has never since been equalled, nor 

 even approached. But he died, refusing to divulge 



