ASSIMILATION AND NUTRITION. 



155 



but at present they are theories, and nothing- more ; and I shall not, therefore, 

 detain you with a relation of them. Thus much, however, we do know, that 

 the co-operation of the atmosphere with the action of the mouths of the se- 

 cernent system engaged in the work of restoration is, in some way or other, 

 pecuiiarly beneficial ; and that, generally speaking, the wider the opening-, 

 and the freer the access of atmospheric air of a due temperature to the sur- 

 face of the wound, or, which is the same thing, the freer it comes in contact 

 with the mouths of the secernent vessels, the more rapidly and auspiciously 

 the work of impletion and assimilation proceeds. Neither do we know, pre- 

 cisely, why pus, rather than any other kind of fluid, should in the first instance 

 be poured forth, for the purpose of filling up the hollow, and producing a rup- 

 ture of the skin ; but we know to a certainty that some such general process 

 is in most cases absolutely necessary ; we know that such a rupture must 

 take place in the natural mode of cure ; that the atmosphere must come into 

 close contact with the mouths of the restorative secernents ; that a milder or 

 softer fluid could not possibly be secreted for such a purpose ; and that the 

 entire process exhibits proofs of most admirable skill and sagacity. It is 

 at times possible for us to assist the process by the lancet, which accelerates 

 the opening. Yet, even in this case, we do no more than assist it, and are 

 only, as we ought ever to be in all similar cases, humble coadjutors and imi- 

 tators of nature, and admirers of that all-perfect and ever-present wisdom 

 which we are so often called upon to witness, but are never capable of 

 rivalling. 



A process closely similar to this is perpetually unfolding in vegetable life. 

 And it was merely by taking advantage of this process that Mr. Forsythe was 

 able to make old, but well-rooted, stumps of fruit-trees throw forth, far more 

 rapidly than he could saplings, a thrifty family of vigorous and well-bearing- 

 shoots : for the compost for which he was so celebrated does nothing more 

 than merely increase the secernent and absorbent action of the vegetable frame 

 by its stimulating property, and defend the wounded part to which it is ap- 

 plied from being injured by the inclemency of the weather. 



From what has thus far been observed, it appears obvious that all the different 

 parts of the living body are assimilating organs, or, in other words, are capa- 

 ble of converting the common nutriment of the blood into their own respective 

 natures, and for their own respective uses. And it has also appeared, that 

 under particular circumstances every part is capable, moreover, of secreting^ 

 a material different from that of its own nature ; as, for example, the material 

 of pus, whenever such a substance is necessary. 



This view of the subject will lead us to understand with facility how it is 

 possible for various organs of the system to maintain two distinct secretions 

 at the same time : one of a matter similar to its own substance, and exclu- 

 sively for its own use ; and another of a matter distinct from its own sub- 

 stance, and in many instances subservient to the system in general. 



Of this last kind are the stomach, the liver, the respiratory organ, and the 

 brain : each of which secretes, independently of the matter for its own nou- 

 rishment, a matter absolutely necessary to the health and perfection of the 

 general machine: as the gastric juice, the curious and wonderful properties 

 of which I described on a former occasion ; the oxygenous principle of the 

 inspired air, and, as some suppose, those of light or caloric ; the bile ; and 

 the nervous fluid, or material of sensation. 



There are various other organs of a smaller kind, and simpler texture, 

 which also perform the same double office, and secrete materials of a much 

 more local use, or which are intended to be altogether thrown away from the 

 system, as waste or noxious bodies. And to the one or the other of these 

 classes belong the kidneys, the intestinal tube, the' minute and very simple 

 perspiratory follicles of the skin, the delicate organs that separate the saliva 

 and mucus that serve to lubricate the mouth and nostrils, and those that ela- 

 borate the tears, the wax of the inner ear, and the fat. 



The organs, of wliatever size or texture, that perform this double function, 

 are called secretory glands ; and they are distinguished into different sets, 



