14 BENNETT, OX THE MOLECULAK THEORY. 



1. By 11 molecule was understood a minute body, seen 

 under high magnifying powers in all organic fluids and tex- 

 tures, A'arying in size from the four thousandth of an inch 

 down to a scarcely visible point, which may be calculated at 

 much less than the twenty thousandth of an inch in diameter. 

 Optically it is distinguished according to its size — the smallest 

 presenting dark or light points as the focus is changed, and 

 the larger exhibiting a dark or light centre, surrounded by a 

 distinctly shadowed ring. These last are frequently dis- 

 tinguished by the name of granules. The ultimate molecule 

 had never been reached even with the highest magnifying 

 powers. In the same manner that the astronomer with his 

 telescope resolves nebulse into clusters of stars, and sees 

 other nebulae beyond them, so the histologist with his micro- 

 scope magnifies molecules into graiuiles, and sees further 

 molecules come into view. The chemical composition of 

 these molecules must vary infinitely, but the author had been 

 in the habit of classifying them into three groups, and referring 

 them to — 1st, the albuminous, 2nd, the fatty, and 3rd, the 

 mineral compounds. These constituents may be mingled 

 together in various proportions, so as to produce simple 

 and compound molecules. In the vast majority of cases 

 they are globular in shape, but they may be angular, square, 

 and of various forms. They may differ in size or be of 

 tolerably uniform size in the same liquid or substance. They 

 may be regularly or irregularly diffused in the matter 

 examined. Sometimes they are concentrated in particular 

 places, and at others scattered in groups. Their colour is 

 various. jNIost of the pigments in plants and animals are 

 dependent on the formation of molecules, Avliich in the 

 human lung have been proved to be pure carbon, and in the 

 tissues of plants and animals differently tinted kinds of fat or 

 of wax. 



These molecules may be formed in two different ways — 

 1st, by precipitation in fluids ; 2nd, by tlie disintegi'ation of 

 previously formed tissues. The former may be called histo- 

 (jenetic {Icttoq and yivzaiq, yeiieratio), and the latter hystolytic 

 [laTog and Xvcng, dissolutio). They may be denominated 

 molecules of formation and molecules of disintegration. 



Histof/enetic molecules are formed either from the union of 

 two simple organic fluids or from precipitations occurring in 

 formative fluids, holding various substances in solution. 

 Fourteen years ago the author read to the society a paper 

 giving an account of the results obtained by a union of oil 

 and liquid albumen, the two organic fluids from which 

 molecular matter is most commonlv derived. It was Dr. 



