FUNCTIONS OF ORGANIC Oil VEGETATIVE LIFE. 227 



Chyle, is propelled through the Lacteals, by the contractility of their walls ; 

 aided in part, perhaps, by a vis a tergo derived from the force of the absorp- 

 tion itself. With the reception of the nutritious fluid into the absorbent ves- 

 sels, commences its real preparation for Organization. Up to that period, it 

 cannot be said to be in any degree vitalised; the changes which it has under- 

 gone being only of a chemical and physical nature, and such as merely prepare 

 it for subsequent assimilation. But in its passage through the long and tor- 

 tuous system of absorbent vessels and glands, it undergoes changes which, 

 with little chemical difference, manifest themselves by a decided alteration in 

 its properties ; so that the chyle of the thoracic duct is evidently a very dif- 

 ferent fluid from the chyle of the lacteals, approaching much nearer to blood 

 in its general characters. These characters are such as indicate that the pro- 

 cess of organization and vitilization has commenced; as may be known alike 

 from the microscopic appearance of the fluid, and from the actions it per- 

 forms when removed from the body. There is reason to believe that the 

 changes, which the Chyle undergoes in its progress through the lacteals, are 

 due to the action of certain cells which are seen to be diffused through the 

 liquid ( 155) ; these, by their own independent powers of growth, are con- 

 tinually absorbing into themselves the fluid in which they float ; whilst, by 

 bursting or liquefying, as soon as their term of life is completed, they give 

 this back in an altered state. The Chyle thus modified is conveyed into the 

 Sanguiferous system of vessels, and flows directly to the heart; by which it is 

 transmitted with the mass of the blood, to the lungs. It there has the oppor- 

 tunity of excreting its superfluous carbonic acid, and of absorbing oxygen ; 

 and probably acquires gradually the properties, by which the blood previous- 

 ly formed is distinguished, thus becoming the pabulum vitse for the whole 

 system. 



272. The Circulation of the Blood through the tissues and organs which 

 it is destined to support, is a process evidently necessary for the conveyance 

 to them of the nutritious materials, which are provided for the repair of their 

 waste ; and for the removal of those elements of their fabric, which are in a 

 state of incipient decomposition. In the lowest classes of organized beings, 

 every portion of the structure is in direct relation with its nutritive materials ; 

 it can absorb for itself that which is required ; and it can readily part with 

 that of which it is desirable to get rid. Hence in such, no general circulation 

 is necessary. In Man, on the other hand, the digestive cavity occupies so 

 small a portion of the body, that the organs at a distance from it have no other 

 means, than their vascular communication affords, of participating in the re- 

 sults of its operations ; and it is moreover necessary that they should be 

 continually furnished with the organizable materials, of which the occasional 

 operation of the digestive process would otherwise afford only an intermitting 

 supply. This is especially the case, as already mentioned, with the Nervous 

 system, which is so predominant a feature in the constitution of Man ; and 

 we accordingly find both objects provided for, in the formation of a large 

 quantity of a semi-organized product, which contains within itself the mate- 

 rials of all the tissues, and is constantly being carried into relation with them. 

 Blood has been not unaptly termed chair coulante, or liquid flesh ; and al- 

 though it has been heretofore much questioned, whether it could be regarded 

 as either organized or endowed with vital properties, there now appears to be 

 sufficient reason for admitting, that this is the case to a very considerable 

 extent. The propulsion of the blood through the large trunks, which subse- 

 quently divide into capillary vessels, is due to the contractions of a hollow mus- 

 cular organ, the Heart; but these, like the peristaltic movements of the ali- 

 mentary canal, are quite independent of (though frequently influenced by) the 



