OF FORCE. 195 



of lime in the paste ; septaria in argillaceous rocks is an example which is quite common 

 in formations of this kind. These concretions are formed there by molecular attraction : 

 it differs from chemical, inasmuch as the new mass is composed of one material, and 

 without having undergone a change, except change of place. 



Molecular force can not be regarded as a force which is influential in producing changes 

 in organic bodies : this is prevented by the activities of the other forces ; when, however, 

 these are diminished, when the force of circulation is diminished by age, concretions of 

 carbonate of lime are found about the large blood vessels and valves of the heart, which 

 operate mechanically in deranging the movements of the apparatus. But these are acci- 

 dents in the animal economy. Something similar to this takes place in vegetables when 

 crystals are formed in the cellular tissue, the bark for instance. These crystals are called 

 raphides by botanists, and are generated in the fluids, and finally crystallize out : they are 

 quite insoluble, and hence remain unaffected by liquids which surround them. In this 

 case, as in the concretion of lime in the vessels about the heart of aged persons, the crystals 

 are foreign bodies, and have nothing to do with the functions of the plant. Molecular 

 force is one of the general forces of inorganic matter, and must be coextensive with gravi- 

 tation. It differs from cohesion. As a common product of many vegetables, it would 

 seem that the formation of starch is the nearest approach to molecular force : but it is 

 scarcely to be regarded as its product, inasmuch as it is still within the reach of the other 

 forces of the plant, and may be transformed into wax and sugar ; it is not, therefore, a 

 crystallization like the raphides, nor a concretion like Septaria in mud deposits ; it is a true 

 secretion, and remains within the influence of the special forces of the plant. 



The forces which are active in plants and animals may be said to reside in the cells ; each 

 cell is an organ, and in one view it may also be said to be an individual, as it performs all 

 the functions of an individual ; the materials which are changed come in contact only with 

 the cell, and it is within this little organ that great results are brought about. 



A single cell then produces gum or a grain of starch, not the compound organ, but the 

 individual cell. A grain of wheat has no force in itself to form starch or gluten ; a cell is 

 first formed, and if the gluten and starch, and gum were dissolved out, the shape of the 

 kernel would remain, and the kernel would be found to consist of many empty cells. The 

 kernel or grain has no force which can produce starch : it would be assuming the existence 

 of a force anterior to the existence of the being exercising it. The kind of force in opera- 

 tion in the tissues of plants and organs of animals is inferred from the phenomena we wit- 

 ness ; and in all cases where the phenomena are different we have a right to infer a dif- 

 ference in the antecedent form : we have no other means of determining the nature of 

 the forces. A magnet moves a bar of iron; sulphuric acid and ammonia combine; mole- 

 cules of carbonate of lime, when diffused through a paste of other materials, unite and 

 form masses : we give the first as a magnetic force, the second as a chemical force, and the 

 third as a molecular force. Water rises in tubes when the bore is extremely small ; it js 

 called capillary attraction. Each example is characterized by peculiar phenomena, and 



