INTRODUCTION. 9 
shortly afterwards cell-nuclei, and subsequently also cells were 
found in all tissues of the animal body at their origin ; so that 
all tissues consist of cells, or are formed by various modes, from 
cells. The other proof of the analogy between animal and vege- 
table cells was thus afforded. 
I shall follow the same course in communicating the separate 
observations, and shall speak, therefore, in the next place of the 
structure and growth of the chorda dorsalis and cartilage, and 
in the second section treat of the germinal membrane and the 
remaining tissues. 
