with that of plants ; and that we do not even know for certain 
that the protoplasm of different kinds of animals is absolutely 
the same. It must also be added that we are still ignorant of 
the precise vital and physiological relations between proto- 
plasm and chlorophyll, the well-known green colouring- 
matter of plants, which plays a most important part in the 
life of the plant, and which, when present at all, is always 
associated with protoplasm. We must remember, therefore, 
that though it is convenient to apply the general name of 
“ protoplasm 33 to the apparently identical living matter of 
all animal and vegetable organisms, we can only infer that 
this substance is really identical in all the cases where we meet 
with it, and that the at present ascertained facts do not 
warrant us in asserting positively that it has a definite and 
invariable chemical composition. 
If protoplasm were an inorganic substance, we should have 
exhausted its essential characters in describing its physical 
properties and its chemical composition. We have, however, 
next to glance at what have been called the “ vital 33 properties 
of protoplasm ; and here we come at once upon a point which 
we shall have to consider again, and which has been, I think, 
too much neglected in all the discussion and controversy which 
has taken place in connection with this substance. I do not 
think, namely, that sufficient distinction has been generally 
made between dead protoplasm and living protoplasm ; and I 
am decidedly of opinion that, with our present knowledge, an 
unwarrantable conclusion has been arrived at by those 
observers — and they are very numerous and influential — who 
have always conducted their argument upon the basis that the 
difference between the two is merely a difference of state. The 
physical properties of protoplasm — as above enumerated — 
have been determined by an examination of protoplasm in 
both its dead and its living condition, and these, therefore, 
may be considered as real and inherent properties of this 
substance. On the other hand, the chemical composition of 
protoplasm can only be determined by an examination of dead 
protoplasm, and we are by no means without examples of the 
almost instantaneous chemical alterations which are apt to 
supervene in highly complex organic compounds when the 
organism passes into that condition which we know as “ death . 33 
We are not, therefore, justified in making the positive assertion 
that living protoplasm has precisely the same chemical com- 
position as dead protoplasm — as far as the constitution of the 
latter may be said to be at all accurately known to us. We 
may infer that the protoplasm of the body — if really a definite 
chemical compound — remains unchanged after death, until 
