74 PRACTICAL HISTOLOGY. 



ration, with their clear oval nuclei and the flattened 

 irregular area occupied by their cell substance. In a 

 few minutes the nuclei will be tinted by the logwood, 

 and will then show up much more prominently ; 

 but to get the cell-bodies sufficiently colored it will 

 be necessary to leave the staining solution half an 

 hour or more in contact with the preparation. Mean- 

 while, to obviate the effects of evaporation, a con- 

 siderable drop of the coloring fluid should be placed 

 on either side in contact with the edges of the cover- 

 glass. The excess of fluid, moreover, has a tendency 

 to raise the latter slightly from the lilm of tissue, 

 and in this way a more ready access of fresh coloring 

 fluid is permitted. When it is found on examina- 

 tion that the corpuscles are properly stained, the 

 solution may be drawn off by a slip of filter-paper 

 applied to the edge of the cover-glass on one side, 

 whilst to the other a drop of distilled water is applied, 

 the logwood being for the most part in this manner 

 rinsed away. The filter-paper is then removed, and 

 a drop of glycerine placed in contact with the edge; 

 this, as the water evaporates, will slowly diffuse it- 

 self under the cover-glass and take its place. It is 

 well to put the preparation aside until the following 

 day, when the process will be completed ; all that is 

 then necessary is to draw a camel-hair pencil wetted 

 with chloroform balsam around the edge of the 

 covering-glass, so as to fix it securely in its place. 



In specimens treated with acid there may be observed 

 a constricting ring at intervals along the course of 

 some of the connective tissue bundles, an appearance 

 which has long been familiar to histologists, but the 

 cause of which is not yet clearly determined, some sup- 

 posing it, from its resistance to the action of acids, to be 

 of the nature of elastic tissue ; others that the appearance 

 is caused by the process of a corpuscle enwrapping the 

 bundle ; the latter opinion being mainly founded on 

 the fact that the ring becomes stained by certain re- 

 agents which also color the cells. For example, as shown 

 by Kanvier, the constricting ring is tinted red by picro- 



