3O6 THE DIGESTIVE ORGANS. 



methods above mentioned for staining mucin may be used to stain the 

 goblet cells. The villi may also be examined in a fresh condition in one 

 of the indifferent fluids. For this purpose the intestine of the mouse is 

 especially well adapted. 



The absorption of fat is best studied in preparations fixed in osmic 

 acid, and especially in those treated by Altmann's method. 



The technic for the solitary lymph -follicles and Peyer's patches 

 is the same as that for lymph-glands. For this purpose the cecum of a 

 rabbit or guinea-pig is the best material. 



The nerves of the intestinal mucous membrane are best demon- 

 strated by means of the methylene-blue method or Golgi's method (vid. 

 Technic), and the coarser filaments of Auerbach'sand Meissner's plexuses 

 may also be stained by the gold method (Lowit's procedure, p. 48). 

 Good results are also obtained by staining with hematoxylin such speci- 

 mens as have been previously fixed and distended with alcohol. The 

 plexuses then appear somewhat darker than the remaining tissue of the 

 isolated mucous membrane or muscular layer. 



Liver. The arrangement of the liver lobules is best seen in the pig's 

 liver. In the human liver and in most domestic animals the lobules are 

 not sharply defined, two or three adjacent lobules merging into each 

 other. In the liver of the fetus, of the new-born, and of children, the 

 lobules are seen indistinctly or not at all, although the peri vascular spaces 

 of the blood-vessels are better seen than in the adult. 



The liver-cells are best examined by treating small pieces of tissue 

 with i o/ osmic acid or osmic mixtures ; in the latter case subsequent 

 treatment with pyroligneous acid is necessary. Good results can also be 

 obtained by fixing with corrosive sublimate and staining with hematoxylin 

 (after M. Heidenhain). 



In order to see the glycogen in the liver-cells Ranvier (89) proceeds 

 as follows : A dog is fed on boiled potatoes for two days, after which 

 sections of its liver are cut with a freezing microtome and examined in 

 iodized serum. In a short time the glycogen is stained a wine-red. If 

 the preparation be now exposed to osmic acid vapor, the stain will remain 

 fixed for from twenty-four to forty -eight hours. Glycogen is insoluble in 

 alcohol and ether, and stains a port wine-red in iodin solutions ; the 

 color disappears when the specimen is warmed, but returns again on cool- 

 ing. 



The distribution of the hepatic blood-vessels is usually demon- 

 strated by injection of the portal vein, as the injection of the hepatic 

 artery does not, as a rule, give such satisfactory results. 



The injection method is also employed for the demonstration 

 of the bile capillaries. Chrzonszczewsky recommends the following 

 so-called physiologic autoinjection : A saturated aqueous solution of 

 indigo-carmin is injected into the external jugular vein three times in the 

 course of one and one-half hours (dog 50 c.c. each time, cat 30 c.c., 

 full-grown rabbit 20 c.c.). The animal is then killed and small pieces 

 of its liver fixed in absolute alcohol or in potassium chlorate ; in the latter 

 case a saturated solution of the salt may be injected into the blood-ves- 

 sels. A subsequent injection of the blood-vessels with carmin -gelatin 

 may also be employed and the whole liver then hardened in alcohol. By 



