LAWS OF ORGANIC DEVELOPMENT. 601 
C. In muscles by simple confluence of cells, end to end and 
mingling of contents (Kölliker). 
D. Of cartilage by formation of cells in cytoblast which break 
up, their contents being added to cytoblast; this occurring sev- 
eral times, the result being an extensive cytoblast with few and 
small cells (Vogt). The process is here an attempt at develop- 
ment with only partial success, the result being a tissue of small 
vitality. 
Even in repair-nutrition recourse is had to the nucleated cell. 
For Cohnheim first shows that if the corner of a frog’s eye be 
searified, repair is immediately set on foot by the transportation 
thither of white or lymph or nucleated corpuscles from the neigh- 
boring lymph heart. This he ascertained by introducing aniline 
dye into the latter. Repeated experiments have shown that this is 
the apite in great part of the construction of new tissue in the 
adult m 
Now, i is well known that the circulating fluid of the fetus 
contains for a period only these nucleated cells as corpuscles, and 
that the lower vertebrates have a greater proportion of these cor- 
puscles than the higher, whence probably the greater facility for 
repair or reconstruction of lost limbs or parts enjoined by them. 
The invertebrates possess only nucleated blood corpuscles. 
What is the relation of cell division to the forces of nature, and 
to which of them as a cause is it to be referred, if to any? The 
animal organism transfers the chemism of the food (protoplasm) 
to correlated amounts of heat, motion, electricity, light (phospho- 
rescence), and nerve force. But cell division is an affection of 
protoplasm distinct from any of these. Addition to homogeneous 
lumps or parts of protoplasm (as in that lowest animal, Protameba 
of Heckel,) may be an exhibition of mere molecular force, or ad- 
dition as is seen in the crystal, but cell division is certainly some- 
thing distinct. It looks to me like an exhibition of another force, 
and though this is still an open question, it may be called for the 
present growth force. It is correlated to the other forces, for its 
exhibitions cease unless the protoplasm exhibiting it be fed. It is 
potential in the protoplasm of both protoplasmic animal mass and 
protoplasmic food, and becomes energetic on the union of the 
two. So long as cell division continues it is energetic; when 
cells burst and discharge the contained cytoblastema, as in the 
formation of cartilage, it becomes again potential. 
