8 THE CAUSATION OF DISEASE. 



Now, according to the theory of Dalton, matter is not 

 continuous, but consists of particles called atoms. This theory 

 has been steadily gaining in .strength since Dalton's time, 

 and is now placed upon a firm basis. There are about seventy 

 different kiuds of atoms. These are united, by what is called 

 chemical force, into molecules, and these latter are, in the case 

 of solids and liquids, held together by the physical force of 

 cohesion. I mentioned kind of matter as one of the material 

 conditions which are at the root of all phenomena. The term 

 refers to the different varieties of atoms. Each kind of atom, 

 we must suppose, possesses certain fundamental, undecompos- 

 able properties, and these properties relate to the power which 

 each atom possesses of attracting to itself other atoms, so as to 

 form different kinds of molecules. It may be that all these 

 atoms are decomposable,* all possibly consisting of different 

 groupings of still smaller particles of only one kind of matter ; 

 and it may also be that the chemical and cohesive forces are 

 but varieties of one force — the universal force of gravitation. 

 Such possibilities must have occurred, I imagine, to most men 

 who have thought carefully over this subject, but whether it 

 be so or not — whether the atoms and these two forces be analys- 

 able or not — none of them have yet been analysed, none 

 therefore have, logically, any cause. We must accept each as 

 a fundamental, undecomposable fact. This remark also applies, 

 of course, to gravity, which itself may possibly not be an 

 ultimate property ; but the possibility of any presumed ulti- 

 mate property being decomposable does not prohibit the 

 assumption of its undecomposability until the reverse is proved. 

 It does not, that is, negative on the ground of illogical treat- 

 ment, the general results arrived at. 



We are now in a position to apply the definition of cause to 



* Loekyer has put forward the hypothesis that all the elements are really 

 compound— i.e., different kinds of aggregation of one kind of matter. Accord- 

 ing to this hypothesis, the matter of which the universe is composed, was at 

 one time equally distributed through space, and uniform in kind, although 

 made up of atoms. These then aggregated into two's, three's, or more, and 

 then again into " elements." This hypothesis rests upon evidence gained by 

 observing different elements under excessively high temperatures (as of the 

 sun) by means of the spectroscope ; the spectroscopic characters suggesting 

 decomposition of the elements into simpler bodies. — Phil. Trans., 1874, V- 49 

 ct eeq. 



