THE INTESTINES. 527 



state of preservation only in quite fresh subjects, and generally breaks 

 up into its elements with extreme ease. The villi are best seen in thin 

 perpendicular sections, made with fine scissors, viewed with a low power, 

 and illuminated from above. During absorption, they are usually found 

 full of fat and nuclei, so that their separate portions are not perceived, 

 with the exception of the lacteals, which become distinct by the use of 

 acetic acid and still better by that of dilute caustic soda. At other 

 times, the muscles of the villi are easily recognized by their nuclei, on 

 the addition of acetic acid. Injections are required for the bloodvessels : 

 the best are made by injecting from both arteries and veins at the 

 same time, and should be preserved in fluid. The same holds good of 

 the other parts of the intestine, for which perpendicular sections are 

 especially instructive. For the glands, recent pieces of intestine are 

 particularly required, although it is often, as in the stomach, exceed- 

 ingly difficult to prepare them. Mucous membrane, hardened in alcohol, 

 pyroligneous acid, or chromic acid, or boiled in acetic acid of 80 per 

 cent, and dried, according to the method of Purkinje and Middeldorpf, 

 or saturated with gum and dried, thin transverse and longitudinal sec- 

 tions being made Avitli a sharp knife, according to Wasmann's method, 

 may be used, being first rendered clear by a little soda. The analysis 

 of the gastric mucous membrane into its elements, presents the greatest 

 difficulties, especially when it is as thick as in the Horse and Pig. In 

 the Dog, Cat, Rabbit, and in the Ruminants, the process is easier, since, 

 frequently, by merely scraping the mucous membrane with the back of 

 a knife, the epithelium of the glands may be drawn out in a connected 

 state and affords all the information required as to their form and lining. 

 Simple teasing out is also frequently sufficient to reduce the mucous 

 membrane of the animals in question into its elements. 



Brunners glands offer no difficulties except in their excretory ducts, 

 which may, however, be clearly seen in perpendicular sections and in 

 animals, by teasing out the mucous membrane. The Lieberklihnian 

 glands, also, may generally be very readily isolated in their entire 

 length ; while the closed follicles should be carefully exposed from 

 without, isolated and opened ; or they may be studied in perpendicular 

 sections. The muscular tissue of the mucous membrane must be exposed 

 by removing the tunica nervea on its exterior and then separating it in 

 small segments from the glandular layer ; its elements maybe very well 

 seen by macerating it in nitric acid of 20 per cent. 



Literature of the intestinal canal. — Th. L. W. Bischoff, " Ueber den 

 Bau der Magenschleimhaut," Mull. Arch. 1838, p. 503, with figures ; 

 AVasmann, " De digestione nonnulla," Berol., 1839, cum tab. ; L. 

 Bcihm, " De glandularum intestinalium structura penitiori," Berol., 

 1835, 8 c. tab. ; and " Die kranke Darmschleimhaut in der Asiatischen 

 Cholera," BerL, 1838 ; J. Henle, " Symbolai ad anatomiam villorum 



