97 



90. It appears then that there must reside a property in the 

 placenta capable of forming oxygen, by an affinity before-mentioned ; 

 a property whose relation with venous blood is to produce an union 

 of its carbon with some oilier constituents of blood, thus yielding 

 eliminated oxygen to the blood, and accomplishing an end which is 

 otherwise brought about by atmospherical communication. This 

 view supposes an antagonist relation between oxygen (derived from, 

 and in proportion to, the maternal nutrient fluid) with the vital pro- 

 perties of the foetal system, and oxygen with the vital properties of 

 the placenta. 



91. In order to satisfy ourselves of the agreement of this 

 solution with the few facts of which we are instructed upon this 

 subject, it is necessary that we should take a view of these facts, so 

 far as they are connected with the question. The fluid imbibed 

 from the mother contains an immense number of constituents which 

 are capable of appearing and acting distinctly, and of being arranged, 

 and of co-existing when subjected to the influence of a mtiteria 

 vitce, or, as we say, an organic spirit resident in the foetus. Before 

 this fluid is subjected to such an influence it appears homogeneous, 

 or at least separable by art into very few constituents (the albumen 

 of an egg, for instance, which in the chick furnishes bones, muscles, 

 arteries, cartilages, nerves, brain, feathers, &c.). This fluid left to 

 itself speedily shews its own tendencies, which may perhaps be 

 called chymical: it soon evaporates or putrifies, and disappears. If 

 the changes which take place in it, in order to accomplish the effects 

 just enumerated, may be called chymical changes (which will here- 

 after be considered), then it is the influence of the principle of life 

 which determines these changes or functions to take place. It is 

 this which changes the relations between the parts of the fluid; it 

 is this, as before explained, possessing different properties in various 

 parts, which acts variously upon the fluid, decomposing and uniting 

 the secret causes of our apparently homogeneous fluid, and alterna- 

 ting these operations, in infinitum. The properties of life are thus 

 related with the parts of the fluid, and these effects are accomplished 

 conformably with the relations in the way of causation before de- 

 scribed. The placenta, it appears, must be a source of oxygen ; it 

 can be a source in no other way than that mentioned at 90. 



92. It will next be inquired how the properties thus related 

 with the venous blood in the placenta come to have so extensive an 

 agency as that which they exert in the maturer periods of foetal 

 existence, when they prepare oxygen for so large a quantity of 

 blood, seeing too how small a sphere they occupied in the original 

 ovum? In answer to this question, it must be seen what is said 

 hereafter under the title of continuance of life, &c. which also exhi- 

 bits processes of growth. 



93. The concurrence necessary to the formation of the tex- 

 tures is, 1st, spiritual properties of the maternal ovum; 2nd, pro- 

 perties of the fecundating principle (these two obey the relations 

 expressed at 16); 3rd, heat; 4th, a nutritious fluid, 

 p 



