202 COMPOSITION AND ARRANGEMENT 



U formed by rows of cells ; so a nervous fibre is nothing more than cells arranged in the same 

 way. Tubes, in their original elementary condition, are rows of cells, the walls of adjacent 

 ends being thinned, till, by loss of matter, they are lacerated ; the tube is then formed. A 

 congeries of tubes makes the vascular system ; a fascile of fibres the muscular, and rows of 

 globules, vesicles or cells, the nervous. All these are woven together by the elementary cel- 

 lular system. But the composition of the several parts is diflFerent. In the vegetable kingdom, 

 a peculiar matter, called cellulose, composes the cells j hence its name : it has its own chemical 

 affinities, and may be tested by reagents. In the animal kingdom, neurine, or nervous matter, 

 has its peculiar constitution ; and so each tissue, or organ, its peculiar constitution. A vegeta- 

 ble is composed, in the main, of cellulose ; but an animal has numerous organs, and the pecu- 

 liar matter of the vegetable, chemical cellulose, is unknown in the animal kingdom, though it 

 constitutes the bulk of the food of most, if not all, animals. The composition of cellulose, 

 according to Muldeb, is, 



Carbon 4491 



Hydrogen, 6*40 



Oxygen 4869 



Iodine and sulphuric acid impart to cellulose a fine blue color, perfectly characteristic of this 

 substance. We advance at once into the region of hypothesis or conjecture, when we attempt 

 to discuss the nature of the force which presides over the formation of cellulose, muscular fibre, 

 neurine and bone. The body is permeated by a homogenous fluid ; the blood, in animals, and 

 the sap, in vegetables ; there is a symmetrical whole, made up of organs diversely constituted. 

 It is a system of unlike parts, united into a unity. The liver, in some of its characters, re- 

 minds us of a kidney. Neurine is infinitely removed from muscular fibre, in its properties and 

 functions ; and yet it is derived from blood. Blood contains the constituents of muscles, 

 nerve and bone ; sap of vegetables, the bark, wood and leaf, chlorophyle, etc. Oils, fats, gum, 

 starch, dextrine, bile, urine, gastric and pancreatic fluids, mucus, saliva, are all products of or- 

 ganization, having a common origin : these are called secretions ; their production seems less 

 mysterious than bone, muscle, neurine and cellulose. These last are formations preceding the 

 first ; and the mode and manner, or the force concerned in separating their elements from an 

 homogenous fluid, the blood, is more familiar to us. Going backwards to their starting points, 

 we can see that molecular groups are produced : we see a fact in natural history ; we know 

 there must be a general law of production, but we can get no farther than to see that a peculiar 

 series of phenomena belong to the formative stage of all organs. To resolve them into a kind 

 of attraction is imsatisfactory, and yet it is the most rational hypothesis which has been framed. 

 Every thing endowed with what we call life exhibits phenomena unlike any thing in inorganic 

 conditions. The formation of iron, in a blast furnace, is preceded by the fusion of many kinds 

 of matters ; the iron separates as the fusion proceeds : the iron existed in the fused mass, as 

 neurine and muscular fibre exist in that plastic material, the blood ; all arc separated from ho- 

 mogenous fluids. But gravity in the iron, and the aflinity of its particles, are principles unlike 



