THE CELL DOCTRINE. 93 



There is an early period of foetal life, previous to 

 the formation of connective tissue, in which we find 

 only embryo-plastic nuclei and fusiform bodies in 

 amorphous matter. This is called embryo-plastic 

 tissue. Growth at this epoch is most rapid, the 

 foetus reaching in a short space of time the dimen- 

 sion of .030 millimetre (.0118 of an inch). 



4th. Germination. This is very frequent in vege- 

 tables, but in animals only one example is known, 

 viz., at a period previous to the fecundation of the 

 ovum. Before segmentation takes place the vitellus 

 is observed to retract. The hyaline substance pushes 

 out a prolongation, which becomes round, separates, 

 and constitutes an independent anatomical element 

 exterior to the vitellus, and bearing no part in the 

 future development of the ovum. 



The following account of certain special elements 

 illustrates and further explains the views of M. 

 Eobin. Red blood globules (hematies), diameter, .007 

 millimetre (-5^3 of an inch); thickness .002 millime- 

 tre (JT^ of an inch). Blood globules are elastic, a 

 property enabling them to elongate, and pass through 

 capillaries which have a calibre less than the diam- 

 eter of the blood globule. They are homogeneous 

 throughout i. e., have no cell wall. Blood globules are 

 formed by genesis in the blood plasma. In the foetus 

 they make their appearance before the white blood 

 globules (leucocytes). In man there are two kinds 

 of red blood globules, viz.: first, embryonic; second, 

 normal. The embryonic blood globules are double 

 the size of the normal ones. They have a slightly 

 granular nucleus, situated nearly in the centre, which 



