180 MANUAL OF HISTOLOGY. 



lymphoid masses, the node must be hardened in alcohol, bi- 

 chromate of potassa, or (Ranvier's method) placed for twenty- 

 four hours in a concentrated solution of picric acid ; sections 

 are then to be made, after which they are gently brushed and 

 agitated in water with a camel' s-hair brush to disengage the 

 lymphoid corpuscles (we are indebted to His for the method of 

 brushing). After staining, preferably with hematoxylin, which 

 exhibits, in a beautiful manner, the lymphoid corpuscles and 

 the darker nuclei of the endothelial layer, they may be 

 mounted in the usual manner. 



Returner's plan. The plan particularly recommended by 

 Ranvier is as follows : the node remains for twenty-four hours 

 in a mixture of alcohol (36 Cartier), one part, water, two 

 parts ; then for twenty-four hours in a syrupy solution of gum- 

 arabic, and is afterward hardened in alcohol sufficiently for 

 section cutting in a microtome. Floating them in a shallow, 

 flat dish, in water two or three centimetres deep, the gum is 

 dissolved, and the brush used in a very delicate manner ; the 

 sections may then be stained and mounted, as described above. 

 The degree of hardness, and the force and duration of the brush- 

 ing process, will determine the result, which practice only will 

 make perfect. The lymphoid corpuscles in the lymph-passages, 

 that is to say, in the parts which fill with the blue injection 

 fluid, as previously described, are first removed, and additional 

 brushing, when the proper degree of hardening has been at- 

 tained, will enable one to remove these bodies from the folli- 

 cles and cords, and also to remove the endothelial cells which 

 rest upon the fibres of the reticulum and septa. 



Other methods of injecting glands. A node removed imme- 

 diately after death and injected by puncture with a 1 per cent, 

 solution of hyperosmic acid, then placed in water for one or 

 two hours, and afterward hardened in alcohol, cut in sections, 

 colored by picrocarminate of ammonia, and mounted, gives 

 good results. 



The best method for showing the endothelial layer is by 

 interstitial injection (puncture) with a solution of nitrate of 

 silver, 1300 ; harden afterward by freezing, and make sec- 

 tions. 



Before closing this chapter, let us take a retrospective view 

 of our subject. In doing so, it is almost impossible to avoid 

 associating the connective- tissue cell with other forms which 



