BY MOLECULAR COALESCENCE. {15 
nearest, in composition and function, to bone. These 
tendons agree almost in every respect with the osseous 
tendons of birds. Both structures give attachment to 
muscular fibres, and are composed of the same chemical 
substances, though in different proportions ; the carbonate 
of lime preponderating in the former, the phosphate of 
of lime in the latter. Now, considering that these struc- 
tures present such marked points of resemblance, and 
differ only in the relative quantities of one of their con- 
stituents, it seems impossible, that they should be formed 
upon totally different principles, and according to dia- 
metrically opposite laws; that is, that the ultimate forms 
assumed by the particles of the one should have been 
determined by physical force, whilst the similar forms 
assumed by the particles of the other should have been 
determined by a vital force; hence, it must be inferred 
that both are produced under the direct influence of the 
same agency, whether it be physical or vital. Now I con- 
' sider that the efficient cause determining the mode of 
arrangement of the substances composing shell-tissues, 
has been demonstrated to be physical ; and therefore, as a 
quod sequitur, the mode of arrangement of the material 
constituents of the osseous tissue must also be physical. 
But as this is so important a question, and as this inference 
is at variance with the opinion of all physiologists, I can- 
not do less than make this tissue a subject of special ex- 
amination. It is a well-known fact, that in every form of 
hard tissue where phosphate of lime is present, there is 
also mixed with it some carbonate of lime. The necessity 
of this combination, and the use of the carbonate of lime 
will be apparent from the following facts. If pure phos- 
phate of lime be formed and deposited, under precisely 
the same conditions as those mentioned in the process for 
