Rev. P. Keith on the Conditions of Life. S9 



life that on which depends the plumpness or embotipoijit of the 

 individual*. 



Of all living bodies whether plants or animals, a notable 

 portion is composed of the fibrous tissue. The fibres are 

 arranged in groups or bundles passing longitudinally through- 

 out the whole extent of the organ, as in the slip of Aspidium 

 Filix-mas ,- or in the nerves, muscles, and tendons of the ani- 

 mal fabric. When viewed superficiallj', a group appears to 

 be merely an individual fibre; but when inspected minutely, 

 and under the microscope, it proves to be made up of fibres 

 smaller and minuter still, firmly cemented together and forming 

 in the aggregate a strong and elastic thread, but capable of 

 being split into a number of component fibriles, till at last 

 they become so fine that you can divide them no longer. But 

 in some organs they are arranged in thin plates or laminae, 

 as in the net-work of the cortical and woody layers of plants; 

 and in the composition of the sclerotica and periosteum of 

 animals f. 



Every organ is invested, and if admitting it, lined, with an 

 envelope of fibrous or of cellular tissue ; and every living in- 

 dividual is enveloped with a covering of bai'k or of skin, or at 

 the least with a fine epidermis. If the tissues are themselves 

 examined with a view to ascertain the elements of their own 

 composition, they will be found to consist of fine films or fibriles, 

 which seem to be themselves composed of multitudes of minute 

 and gelatinous globules closely compacted together, and dis- 

 tinguishable only by the microscope. Their diameter is re- 

 presented as not exceeding the u^q'q ^th part of an inch ; but 

 their existence is by some doubted. Beyond this, the analysis of 

 the dissector cannot go. Here his anatomy ends. If he pro- 

 ceeds to chemical analysis, he will find that the proximate prin- 

 ciples of the animal solids are chiefly albumen, fibrin, gelatin ; 

 the remote principles being azote, oxygen, hydrogen, caibon, 

 with the azote predominating:):. 



Of the vegetable solids he will find that the proximate 

 principles are chiefly albumen, fibrin, gluten, sugar, gum, 

 extract; the remote principles being carbon, hydrogen, oxy- 

 gen, with the carljon predominating §. When the proximate 

 principles of animals, albumen, fibrin, gelatin, are converted 

 artificially from a fluid to a solid state, as by the action of 

 heat or of other chemical agents, multitudes of minute globules, 

 similar to those of the blood, are said to be develoj)ed in the 



• Anatomic G'nurale, par M. Bichilt. 98. 



t Anat. Gtnirale, torn. ii. 251. X Magcndic, by Milligaii. 10. 



§ Davy's Agricultural Lectures. 



