54 LECTURE II. 



a fluid, but that, under certain circumstances, they 

 gathered together, not in the form of vesicular mem- 

 branes, but so as to constitute a compact heap, a globe 

 (mass, cluster Kliimpchen), and that this globe was the 

 starting point of all further development, a membrane 

 being formed outside and a nucleus inside, by the diffe- 

 rentiation of the mass, by apposition, or intussusception. 

 At the present time, neither fibres, nor globules, nor 

 elementary granules, can be looked upon as histological 

 starting-points. As long as living elements were con- 

 ceived to be produced out of parts previously destitute 

 of shape, such as formative fluids, or matters (plastic 

 matter, blastema, cytoblastema), any one of the above 

 views could of course be entertained, but it is in this 

 very particular that the revolution which the last few 

 years have brought with them has been the most 

 marked. Even in pathology we can now go so far as to 

 establish, as a general principle, that no development of 

 / any hind begins de novo, and consequently as to reject 

 / the theory of equivocal [spontaneous] generation just as 

 \ much in the history of the development of individual parts 

 \as 'we do in that of entire organisms. Just as little as 

 we can now admit that a taenia can arise out of saburral 

 mucus, or that out of the residue of the decomposition 

 of animal or vegetable matter an infusorial animalcule, a 

 fungus, or an alga, can be formed, equally little are we 

 disposed to concede either in physiological or pathologi- 

 cal histology, that a new cell can build itself up out of 

 any non-cellular substance. Where a cell arises, there a 

 cell must have previously existed (omnis cellula e cellula), 

 just as an animal can spring only from an animal, a 

 plant only from a plant. In this manner, although there 



granules, b. Heap of granules (cluster), c. Granule-cell, with membn?tie and 

 nucleus. 



