1130 THE NUTRITION OF THE EMBRYO. [BOOK 



time histological differentiation has advanced largely, and the 

 use of the glycogen to the economy has become that to which 

 it is put in the ordinary life of the animal ; hence we find it 

 deposited in the usual place. We do not know how much car- 

 bohydrate material finds its way into the umbilical vein ; and 

 we cannot therefore state what is the source of the foetal glyco- 

 gen ; but it is at least possible, not to say probable, that it 

 arises, in part at all events, from a splitting up of proteid 

 material in the foetal body. 



701. Concerning the rise and development of the func 

 tional activities of the embryo, our knowledge is almost a blank. 

 We know scarcely anything about the various steps by which 

 the primary fundamental qualities of the living matter of the 

 ovum are differentiated into the complex phenomena which we 

 have attempted in this book to expound. We can hardly state 

 more than that while muscular contractility becomes early 

 developed, and the heart probably, as in the chick, beats even 

 before the blood-corpuscles are formed, movements of the foetus 

 are in the human subject first felt about the sixteenth week ; 

 they probably occur before but are not easily recognized, while 

 from that time onward they increase and subsequently become 

 very marked. They are often spoken of as reflex in character, 

 and some of them are undoubtedly of this nature. When the 

 uterus of a pregnant animal is prematurely opened, various 

 reflex movements of the foetus may be excited by appropriate 

 stimulation, different kinds of animals differing in this respect 

 as they do with regard to the powers of the new-born animals. 

 Such reflex movements may be witnessed before the placental 

 circulation has been interrupted, but they are increased if the 

 foetus be made to breathe. We have already referred to swal- 

 lowing movements ; and may add that an immature foetal ani- 

 mal may be made to bite by introducing the finger into its 

 mouth. Some of these normal intra-uterine movements appear 

 however to be not reflex but automatic if not voluntary in 

 nature. Movements of the limbs, apparently automatic, have 

 been observed in foetuses in which the brain has not been 

 developed. We may add that in the human subject the occur- 

 rence of intra-uterine convulsions is fully acknowledged. 



702. The digestive functions are naturally, in the absence 

 of all food from the alimentary canal, in abeyance. Though 

 pepsin may be found in the gastric membrane at about the 

 fourth month, it is doubtful whether a truly peptic gastric juice 

 is secreted during intra-uterine life ; trypsim appears in the 

 pancreas somewhat later, but an amylolytic ferment cannot be 

 obtained from that organ till after birth. The date however 

 at which these several ferments make their appearance in the 

 embryo appears to differ in different animals. The excretory 

 functions of the liver are developed early, and about the third 



