554 THE REPRODUCTIVE FUNCTIONS. 



cannot but be forcibly struck with the numerous 

 forms of transition through which every organ has 

 to pass before arriving at its ultimate and compa- 

 ratively permanent condition : we cannot but won- 

 der at the vast apparatus which is provided and 

 put in action for effecting all these changes; nor 

 can we overlook the instances of express contriv- 

 ance in the formation of so many temporary struc- 

 tures, which are set up, like the scaffold of an 

 edifice, in order to afford the means of transporting 

 the materials of the building in proportion as they 

 are wanted ; nor refuse to recognise the evidence 

 of provident design in the regular order in which 

 the work proceeds, every organ growing at its 

 appointed time, by the addition of fresh particles 

 brought to it by the arteries, while others are car- 

 ried away by the absorbents, and are gradually 

 acquiring the form which is to qualify it for the 

 performance of its proper office in this vast and 

 complicated system of animal life. 



the second, " la loi de conjugaison.'' He maintains that they are 

 strictly applicable to all the parts of the body having a tubular form, 

 such as the trachea, the Eustachian tube, the canals and perfora- 

 tions of bones, &c. See the preliminary discourse to his " Anatomie 

 comparee du cerveau," p. 25 ; and also his several memoirs in the 

 " Annales des Sciences Naturelles," vols. xi. xii. xvi. and xxi. 



An excellent summary of the principal facts relating to the deve- 

 lopement of the embryo is given by Mr. Herbert Mayo, in the third 

 edition of his " Outlines of Human Physiology." 



