7 8 PRACTICAL HISTOLOGY. 



frequently. Continuous on each side with the trabeculae is the adenoid tissue, stretching 

 across the lymph-space (PI. XVII., Fig. 4). Blue-stained nuclei are seen at the nodal points 

 of the fibres (PI. XVII., Fig. 6). As already shown (p. 29), they are the nuclei of squames 

 which cover these fibres. The meshes contain few leucocytes. Study a patch loaded with 

 lymph-corpuscles, and also a transverse section of a trabecula with its lymph-space around 

 it (PI. XVI L, Fig. 5). This is most easily found in the medulla. 



The picric acid and picrocarmine section shows similar details. 



Refer also to the preparations of adenoid tissue prepared by the interstitial injection of a 

 solution of silver nitrate, which demonstrates the endothelium lining the lymph-sinuses (p. 29). 



Injection of the Lymph-Sinuses. PREPARATION. With a hypodermic syringe inject into 

 the lymphatic gland of an ox a two per cent, watery solution of Prussian blue. Place the 

 gland in alcohol for twenty-four hours, and then make transverse sections. Stain a section 

 with carmine, and mount it in Farrant's solution. 



EXAMINATION (L). Observe the distribution of the blue deposit around the follicles in 

 the cortex, and around the trabeculae in the medulla. This method indicates beautifully the 

 position of the lymph-sinuses. 



Blood-vessels. Study a section where the blood-vessels have been injected, and note that 

 the large vessels lie in the trabeculs, whilst the capillaries are almost entirely confined to the 

 glandular substance. 



(B.) SIMPLE LYMPHATIC GLANDS. 



These consist of masses of adenoid tissue occurring in the form of spherical or nodular 

 masses, either singly or in groups, or sometimes in the form of cords. They have already 

 been referred to as occurring in the tonsils (p. 65), at the root of the tongue (p. 61), epiglottis 

 (p. 53), trachea (p. 54), and lungs (p. 59), (especially in the lungs of the cat), in the pyloric 

 end of the stomach (p. 67), throughout the intestine as solitary glands (p. 70), and in groups, 

 as Peyer's patches, in the small intestine (p. 69). They also occur in the spleen (p. 79) as 

 Malpighian corpuscles. They form the basis of the thymus gland (p. 81). 



THE SPLEEN. 



It is desirable to examine the spleen of one of the lower animals, say a cat, as well as that 

 of man. 



(A.) CAT. 



PREPARATION. Cut the spleen of a cat into five or six pieces, and harden them first in 

 M tiller's fluid ; at the end of a week place them in chromic acid and spirit mixture, and after 

 another week transfer them to spirit. Make transverse sections. Stain a section in logwood 

 and mount it in dammar. 



(B.) HUMAN. 



Cut a fresh normal human spleen into small pieces, and harden them in the same way as 

 the above, but leave them two weeks in the chromic acid and spirit fluid. Make sections of a 

 part, and include the fibrous capsule. Stain a section in logwood, and mount it in Farrant's 

 solution. 



