BENNETT, ON THE MOLECULAR THEORY. 43 



With regard to the second problem, the only possible 

 direct mode of lessening the evil is, as it appears to me, to 

 examine the leaves when the mangolds are young, and when, 

 in consequence, they are most likely to be injured, and 

 to crush between the finger and thumb the little groups of 

 ova Avhich can readily be detected by the naked eye ; of coui'se 

 this would demand a good deal of valuable time, and, per- 

 haps, for this very reason, may be deemed altogether impracti- 

 cable. There can be no doubt that many of our smaller birds 

 are of great use to us in helping to diminish the extent 

 of the iiijuiy, and since the first appearance of the larv(B of 

 this destructive insect is contemporary vdili the time when 

 birds are very busy seeking food for their young, perhaps 

 the farmer's best policy is to abstain from an indiscriminate 

 slaughter of the feathered tribes, and to leave with them the 

 chance of being of considerable benefit to him. 



On the Molecular Theory of Organization. By 

 Professor Bennett, M.D., F.R.S.E., &c. 



(From the Proceedings of the lloyal Society of Edinburgh, April 1, 1861.) 



Parodying the celebrated expression of Harvey, viz., 

 omne animal ex ova, it has been attempted to formidarise the 

 law of development by the expression omnis cellula e cellula, 

 and to maintain " that we must not transfer the seat of real 

 action to any point beyond the cell.-"'^ In the attempts 

 which have been made to support this exclusive doctrine, 

 and to give all the tissues and all vital properties a cell 

 origin, the great importance of the molecular element, it 

 seemed to the author, had been strangely OA^erlooked. It 

 becomes important, therefore, to show that real action, both 

 physical and \ital, may be seated in minute particles, or 

 molecules much smaller than cells, and that we must obtain 

 a knowledge of such action in these molecules if we desire to 

 comprehend the laws of organization. To this end the 

 author directed attention — 1st, to a description of the nature 

 and mode of origin of organic molecules ; 2nd, to a demon- 

 stration of the fact that these molecules possess inherent 

 powers or forces, and are present in all those tissues which 

 manifest vital force ; and 3rd, to a law which governs the 

 combination, arrangement, and behaviour of these molecules 

 during the development of organized tissue. 



* Vircliovr, 'Eng. Trans,,' p. 3. 



