8 HISTO-CHEMISTRY. 



tion to the strength of the solutions employed in micro-chemistry. 

 A disregard of this rule frequently led in earlier times to the most 

 discrepant statements regarding the action of various reagents on 

 blood and pus corpuscles, and at the present day we may possibly 

 ascribe to the same cause the very different assertions that have 

 been made regarding the action of various chemical matters on 

 certain tissues, We shall presently see, for instance, what dif- 

 ferent effects are produced on muscular tissue by extremely dilute, 

 moderately dilute, and concentrated hydrochloric acid, and what 

 different consequences result from the application of alkaline 

 solutions of various strengths to similar objects. Whilst the 

 chemist throws together organised parts, crushes the organic mass 

 in a mortar, and then most laboriously attempts to fish out the 

 individual constituents, always, however, carefully paying attention 

 to his chemical reagents, and the manner in which they should be 

 applied, the micro-chemical inquirer has often followed a totally 

 opposite course; he may have observed the alterations in form 

 which the object has undergone, while he has not sufficiently 

 attended to the nature of the chemical reagents he has employed ; 

 indeed, they sometimes seem to be selected at hap-hazard, and 

 are of such a nature that they cannot lead to chemically serviceable 

 results, their application being so irrational in a chemical point of 

 view that, let their action be what it may, no conclusive results 

 can be expected from them. These remarks lead us to another 

 point in micro-chemical analysis, to which we should pay the most 

 serious attention, and by the neglect of which we lose many most 

 important results. 



It is obvious that micro-chemical reagents should be applied 

 for other purposes than merely for the object of studying the 

 changes of form which the elementary tissues undergo, and of 

 investigating their minute structure, or of determining whether 

 this or that histological element be the more nearly allied to that 

 hypothetical substance, protein, or whether it rather falls into the 

 very vague category of " gelatigenous tissue," or whether it be 

 altogether different from either. Micro-chemical investigation 

 must be pursued with the same aims as every other chemical 

 manipulation, that is to say, it must be directed to the elucidation 

 of the chemical constitution of the object under consideration, and 

 must indicate the direction to be followed in our advance towards 

 the goal of our inquiries. But this point will not be attained 

 as long as we content ourselves with employing this or that 

 reagent at random, and are satisfied with observing the alteration 



