4 i8 GENERATION. SECT. XXXIX. 9. 2. 



tial parts of the fetus, as the brain and heart, with all the upper 

 parts of the body, and interlines, would feem to be attended with 

 flill greater difficulties. 



The miftake of conceiving the embryon to begin its forma- 

 tion in one point only might more readily be fallen into from 

 our habitually confidering an animal as an individual entity ; 

 which it feems not to be, till an union of the nerves from every 

 part is formed in the common fenforium, and produces a gener- 

 al fenfibility, which is thus diflinguifhed from irritability, 

 which may refide in parts even when detached from the fyitem, 

 as is feen in the contractions of the heart of a viper taken out 

 of the body, or of limbs recently cut off, 



2. Another thing difficult to conceive from thofe theories, 

 which fuppoied the firft rudiment to confift of a fmgle entity, 

 was to anfwer the curious queftion, whether the brain, or heart 

 and arteries were firft formed ; as the motions of the arterial 

 fyftem previoufly exerted feem to have been necefTary for the 

 fecretion of fenforial power in the brain, and converfely thofe 

 motions of the arterial fyftem feem previoufly to require 

 the fenforial power derived from the brain. 



This difficulty vanifhes, when we believe, that many parts of 

 the young embryon can be begun at the fame time, as various 

 formative fibrils and formative molecules coalefce, as they come 

 into contact, with each other ; and thus the rudiments of the brain 

 and of the heart may be fabricated at the fame inftant of time. 



3. If fibrils with formative appetencies, and molecules with 

 formative aptitudes or propenfities exifl in the circulation both 

 of males and females, why do they not coalefce there ? This 

 feems an unanfwerable objection to M. BufFon's theory, who 

 holds, that organic particles exifl in the circulation ; but in the 

 fyftem above delivered, no organic particles exifl in the blood in 

 their combined ftate ; and hence no microfcopic animalcula are 

 feen in blood recently drawn, though they may appear after fome 

 hours flagnation ; but the formative fibrils only and formative 

 molecules are believed to exift in the circulation ; and that they 

 do not produce combinations there, as they cannot reft ; and as 

 fuch combinations would be too large to pafs the capillary vef- 

 fels of the aorta, and of the pulmonary artery, and of all the 

 glands, and muft there be perpetually diflevered, if they could 

 be previoufly formed in the larger veflels. 



4. If fimilar organized particles were fecretcd by the fexual 

 glands of the male and alfoof the female, why do they not pro- 

 duce parts, or rudiments, of an embryon in the male or female 

 yefervoirs without a reciprocal commixture. This is another 

 Unanfwerable objection to M. BufFon's theory, but not to that 



above 



