76 DR. BEALEj ON THE TISSUES. 



wliich are destitute of nuclei. The mode of formation of 

 these structures will be presently discussed. 



At an early period of development this form of connective 

 tissue is absent. There are only traces of it in the foetus at 

 the seventh or eighth months but it is found in increased 

 quantity in the tissues of the child, and in still greater pro- 

 portion in the adult. In some situations Dr. Beale thinks he 

 has demonstrated that it increases as age advances, but at 

 the same time it' undergoes condensation, and therefore 

 occupies less space. In disease it is often increased in situa- 

 tions where only traces are present in health, and it is found 

 in situations where it is absent in the normal state. It is 

 frequently present in large quantity in situations from which 

 higher tissues have disappeared. 



During the process of development tissues which serve but 

 a temporary purpose are constantly being replaced by the 

 growth of higher and more permanent structures. The com- 

 plex tissue which exists in the adult is represented in the 

 embryo by a much more simple type, which is removed and 

 replaced often by several series of textures before a tissue like 

 that of the adult is produced. The tissues are not developed in 

 their permanent form, and do not simply increase as the body 

 grows, but those textures which perform certain functions in 

 the adult, are represented in the embryo by tissues which 

 perform corresponding, but not exactly similar offices. Not 

 only have the permanent glands certain temporary substi- 

 tutes, differing from them in important points, but the struc- 

 ture of the different tissues, muscle, nerve, bone, &c., be- 

 comes modified as development proceeds, until the permanent 

 type of structure is reached. At the sixth or seventh 

 month of intra-uterine life it is not possible to trace the 

 representatives of all the adult structures, in the finger, for 

 instance ; most active changes are occurring, and it is quite 

 evident that the newly formed tissues are growing and en- 

 croaching upon structures which attained their maximum of 

 development at an earlier period. The nerve fibres and vessels 

 alter as much as any other tissues. A space which in a given 

 position in the foetalfinger contains only capillaries and terminal 

 nerve fibres, will, at a later period, contain arteries, veins, and 

 nerve trunks, as well as capillaries and terminal branches, and 

 later still, will contain, and perhaps be entirely occupied with, 

 large arterial and venous trunks, and bundles of trunks of 

 nerve fibres. The Pacinian corpuscles, the sweat glands, and 

 the papillse are all to be seen, but their structm-es and relations 

 are very different when development is more advanced. There 

 are no sudden changes, no sudden transitions from one tissue 



