ON THE SALIVARY GLANDS. 
399 
positive distinctions, enabling us to establish modifications and 
gradations between the salivary organs, according as they ap¬ 
pear to us in mammiferous and the other classes of vertebrated 
animals. 
Experiment has taught us, in fact, that, in the mammifera, the 
three salivary glands, properly so called, secrete fluids not 
physically identical, which has led to the belief of their being 
three distinct salivary agents, one for gestation, another for 
mastication, and a third for deglutition; and that the physico¬ 
chemical properties of each are quite in accordance with these 
different physiological distinctions. The saliva of the parotid, 
not viscid but watery, penetrates and readily dissolves sub¬ 
stances; whereas, on the contrary, the saliva furnished by the 
sublingual and buccal glands, viscous and glutinous, is admi¬ 
rably suited for enveloping the alimentary bolus, and for in¬ 
creasing its coherence and facilitating its gliding properties; 
while the submaxillary saliva, from possessing a mixed cha¬ 
racter, at once operates as a solvent, and loosens or binds the 
sapid matters, at the same time that it has the effect of lubri¬ 
cating the surfaces and diminishing the rudeness of contact. 
The author sums up his paper in these terms :—It follows, from 
the facts adduced, — 
1. That anatomy exhibits the groups of glands, called salivary , 
to us as an homogeneous apparatus, the different organs of which 
their texture shews to be identical. 
2. That experimental, physiological analysis on the contrary, 
while it demonstrates the difference of their secretions, and di¬ 
rects our view to the nervous influences regulating the secre¬ 
tions, teaches us that each gland has a special function which it 
exercises under separate and independent agency. Notwith¬ 
standing the diffusion and commingling of the different salivae 
within the mouth, their uses remain distinct; experience inform¬ 
ing us, that the function belonging to the parotid secretion is that 
of aiding mastication; that of the submaxillary, gustation; and 
that of the sublingual and buccal glands, aiding deglutition. 
It is by such physiological facts alone that we are able to 
investigate and understand, in their veritable signification, the 
modifications the salivary organs undergo in the different 
species of vertebrate animals. The true characteristic of their 
salivary glands should not be sought for either in the anatomical 
structure, the volume, or the form of the glands, but in the na¬ 
ture of the function they are designed for. Consequently, it is 
contrary to just physiological principle to follow the example of 
some anatomists, such as J. F. Meckel, and pretend to find parotid 
and submaxillary glands in birds wherein they have no exist¬ 
ence, when it is known that these animals in general lack the 
