:

of inquiry and thought since that time, but it appears to the Author that, great as discussion has been, there are yet considerations respecting vitality that have not been duly weighed. Whether living matter was formed originally, or is now being formed, from non-living matter, by the operation of physical causes and natural laws, are questions which, notwithstanding the lively and vigorous handling which they have had, are far from being settled. Exact experiment can alone put an end to this dispute the one conclusive experiment, indeed, in proof of the origin of living from dead matter, will be to make life. Meanwhile, as the subject is still in the region of discussion, it is permissible to set forth the reflections which the facts seem to warrant, and to endeavour to indicate the direction of scientific development which seems to be foretokened by, or to exist potentially in, the knowledge which we have thus far acquired. This much may be said that those who oppose the doctrine of so-called spontaneous generation, not on the ground of the absence of conclusive evidence of its occurrence, which they might justly do, but on the ground of what they consider special characteristics of living matter, would do well to look with more insight into the phenomena of non-living nature, and to consider more deeply what they see, in order to discover whether

the characteristic properties of life are quite so special and exclusive as they imagine them to be. Having done that, they might go on to consider whether, even if their premisses were granted, any conclusion regarding the mode of origin of life would legitimately follow; whether in fact it would not be entirely gratuitous and unwarrantable to conclude thence the impossibility of the origin of living matter from non-living matter. The etymological import of the words physics and physiology is notably the same; and it may be that, as has been suggested, in the difference of their application lies a hidden irony at the assumption on which the division is grounded.

9, HANOVER SQUARE, W.

November 5, 1870.

CONTENTS.

LECTURES.

I. ON THE PHYSICAL CONDITION OF MENTAL FUNCTION

IN HEALTH

2. ON CERTAIN FORMS OF DEGENERACY OF MIND, THEIR

CAUSATION, AND THEIR RELATIONS ΤΟ OTHER

DISORDERS OF THE NERVOUS SYSTEM

3. ON THE RELATIONS OF MORBID BODILY STATES TO

DISORDERED MENTAL FUNCTIONS

APPENDIX.

PAGE

I

40

77

I. THE LIMITS OF PHILOSOPHICAL INQUIRY

115

2. THE THEORY OF VITALITY

143

LECTURES.

1. ON THE PHYSICAL CONDITION OF MENTAL

FUNCTION IN HEALTH.

2. ON CERTAIN FORMS OF DEGENERACY OF MIND, THEIR CAUSATION, AND THEIR RELATIONS

TO OTHER DISORDERS OF THE NERVOUS

SYSTEM.

3. ON THE RELATIONS OF MORBID BODILY STATES TO DISORDERED MENTAL FUNCTIONS.