THE CORPUSCLES OF THE BLOOD. 47 



to enable us to judge, by optical characters, what is really living and what 

 is not. 



The material which appears in the cell body in the form of distinct 

 granules, merely lodged in the more transparent material, cannot be part 

 of the real living substance ; it must be either food or waste. Many of 

 these granules are fat, and we have at times an opportunity of observing 

 that they have been introduced into the corpuscle from the surrounding 

 plasma. The white corpuscle, as we have said, has the power of executing 

 amoeboid movements ; it can creep around objects, envelope them with its 

 own substance, and so put them inside itself. The granules of fat thus in- 

 troduced may be subsequently extruded or may disappear within the cor- 

 puscle ; in the latter case they are obviously changed, and apparently made 

 use of by the corpuscle. In other words, these fatty granules are apparently 

 food material on their way to be worked up in the living substance of the 

 corpuscle. 



But we have also evidence that similar granules of fat may make their 

 appearance wholly within the corpuscle ; they are products of the activity of 

 the corpuscle. We have further reason to think that in some cases, at all 

 events, they arise from the breaking down of the living substance of the 

 corpuscle, that they are what we have called waste products. 



But all the granules visible in a corpuscle are not necessarily fatty in 

 nature ; some of them may undoubtedly be proteid granules, and it is possi- 

 ble that some of them may at times be of carbohydrate or other nature. In 

 all cases, however, they are either food material or waste products. And 

 what is true of the easily distinguished granules is also true of other sub- 

 stances, in solution or in a solid form, but so disposed as not to be optically 

 recognized. 



Hence a part, and it may be no inconsiderable part, of the white corpus- 

 cle, may be not living substance at all, but either food or waste. Further, it 

 does not necessarily follow that the whole of any quantity of material, fatty 

 or otherwise, introduced into the corpuscle from without, should actually 

 be built up into and so become part of the living substance; the changes 

 from raw food to living substance are, as we have already said, probably 

 many, and it may be that after a certain number of changes, few or many, 

 part only of the material is accepted as worthy of being made alive, and 

 the rest, being rejected, becomes at once waste matter ; or the material may, 

 even after it has undergone this or that change, never actually enter into 

 the living substance, but all become waste matter. We say waste matter, 

 but this does not mean useless matter. The matter so formed may without 

 entering into the living substance be of some subsidiary use to the corpuscle, 

 or, as probably more often happens, being discharged from the corpuscle, 

 may be of use to some other part of the body. We do not know how the 

 living substance builds itself up, but we seem compelled to admit that, 

 in certain cases at all events, it is able in some way or other to produce 

 changes on material while that material is still outside the living substance 

 as it were, before it enters into and indeed without its ever actually entering 

 into the composition of the living substance. On the other hand, we must 

 equally admit that some of the waste substances are the direct products of 

 the katabolic changes of the living substance itself were actually once part 

 of the living substance. Hence we ought, perhaps, to distinguish the products 

 of the activity of living matter into waste products proper, the direct results 

 of katabolic changes, and into by-products which are the results of changes 

 effected by the living matter outside itself, and which cannot, therefore, be 

 considered as necessarily either anabolic or katabolic. 



Concerning the chemical characters of the living matter itself we cannot 



