British Association . 
1879.] 
633 
supposed antagonism in its respective character is totally 
demolished. 
Enough has been said to show that in protoplasm we find the 
only form of matter in which life can manifest itself. We are 
thus led, said Prof. Allman, to the conception of an essential 
unity in Organic Nature, — a structural unity in as far as every 
living being has protoplasm as the essential matter of every 
living element of its structure, and a physiological unity in the 
universal attribute of irritability, which has its seat in this same 
protoplasm, and is the prime mover of every phenomenon of 
life. Mere form has little to do with the essential properties of 
protoplasm. To suppose that all protoplasm is identical where 
no difference can be detected by the means at our disposal would 
be an error. Of two particles of protoplasm between which we 
can deteCt no difference, one can develop only to a jelly-fish, the 
other only to a man ; and one conclusion alone is possible — that 
deep within them there must be a fundamental difference which 
thus determines their destiny. Of this we know nothing, and 
can assert nothing beyond the statement that it must depend on 
their hidden constitution. In the molecular condition of proto- 
plasm there is probably as much complexity as in the disposition 
of organs in the most highly differentiated organisms. Herein 
lies the many-sidedness of protoplasm, and its significance as the 
basis of all morphological expression, as the agent of all physio- 
logical work. From the faCts which have been here briefly 
noticed there is but one legitimate conclusion — that life is a pro- 
perty of protoplasm. The essential phenomena of living beings 
are not so widely separated from the phenomena of lifeless 
matter as to render it impossible to recognise an analogy between 
them. Even irritability, the one grand character of living beings, 
is not more difficult to be conceived of as a property of matter 
than the physical phenomena of radial energy. It is quite true 
that between lifeless and living matter there is a difference greater 
far than any which can be found between the most diverse mani- 
festations of lifeless matter. No one has ever yet built up one 
particle of living matter out of lifeless elements. Every living 
creature has its origin in pre-existent living matter ; the proto- 
plasm of to-day is but the continuation of the protoplasm of past 
ages. When we say that life is a property of protoplasm we 
assert as much as we are justified in doing. We stand upon the 
boundary between life in its proper conception, as a group of 
phenomena having irritability as their common bond, and that 
other group of phenomena which we call consciousness or 
thought, and which, however closely linked with those of life, 
are yet essentially distinct from them. When a thought passes 
through the mind it is associated, as we have reason for believing, 
with some change in the protoplasm of the cerebral cells. Are 
we therefore justified in regarding thought as a property of the 
protoplasm of these cells, in the sense in which we regard mus- 
