58. =Certain Constituents of the Body are very similar in the Wheat Plant and in the Fowl.= The wheat plant contains neither horn, nor gelatin, and the fowl contains neither starch, nor cellulose; but the albumin of the plant is very similar to that of the animal, and the fibrin and syntonin of the animal are bodies closely allied to both albumin and gluten. That there is a close likeness between all these bodies is obvious from the fact that when any of them is strongly heated, or allowed to putrefy, it gives off the same sort of disagreeable smell; and careful chemical analysis has shown that they are, in fact, all composed of the elements =Carbon=, =Hydrogen=, =Oxygen=, and =Nitrogen=, combined in very nearly the same proportions. Indeed, =charcoal=, which is impure carbon, might be obtained by strongly heating either a handful of corn, or a piece of fowl’s flesh, in a vessel from which the air is excluded so as to keep the corn or the flesh from burning. And if the vessel were a still, so that the products of this =destructive distillation=, as it is called, could be condensed and collected, we should find water and ammonia, in some shape or other, in the receiver. Now ammonia is a compound of the elementary bodies, nitrogen and hydrogen; therefore (§ 50) both nitrogen and hydrogen must have been contained in the bodies from which it is derived. It is certain, then, that very similar nitrogenous compounds form a large part of the bodies of both the wheat plant and the fowl, and these bodies are called =proteids=. 59. =Proteid Substances are met with in Nature only in Animals and Plants; and Animals and Plants always contain Proteids.= It is a very remarkable fact that not only are such substances as albumin, gluten, fibrin and syntonin, known exclusively as products of animal and vegetable bodies; but that every animal and every plant, at all periods of its existence, contains one or other of them, though, in other respects, the composition of living bodies may vary indefinitely. Thus, some plants contain neither starch nor cellulose, while these substances are found in some animals; while many animals contain no horny matter and no gelatin-yielding substance. So that the matter which appears to be the =essential= foundation of both the animal and the plant is the =proteid= united with =water=; though it is probable that, in all animals and plants, these are associated with more or less =fatty= and =amyloid= (or starchy and saccharine) substances, and with very small quantities of certain mineral bodies, of which the most important appear to be =phosphorus=, =iron=, =lime=, =and potash=. Thus there is a substance composed of water + proteids + fat + amyloids + mineral matters which is found in all animals and plants; and, when these are alive, this substance is termed =protoplasm=. 60. =What is meant by the word Living?=