ON COMPARATIVE PHYSIOLOGY. 
65 
result of an assemblage of heterogenous 
parts, or if, sometimes, they present this 
character, the parts are only simply mixed 
with each other. Generally speaking, crys- 
tals are composed only of homogenous solid 
jjarts.* 
XXX. Inasmuch as organic bodies are com- 
posed of liquids and solids, it follows as an 
immediate result, that they possess but little 
consistency and rigidity* All of them are 
soft and flexible, either throughout, or in a 
great number of their parts. In fact, their 
consistence varies considerably, as well in 
vegetables as in animals, and not only in the 
different groups of living bodies, but even in 
the different parts of each individual. In ge- 
neral, we remark that the more irnportant 
parts of these bodies, those parts which per- 
form the principal offices in the accomplish- 
ment of their special manifestations of activi- 
ty, possess the smallest consistence and soli- 
dity, such as the fibres of the roots, the sap 
vessels, the alburnum, the leaves and flowers 
in plants ; the nerves, brain, muscles, the 
viscera intended for the process of digestion, 
and of respiration, and those destined to the 
movement of the humours and to the differ- 
ent secretions in animals. '1 he consistence 
varies also in proportion to the age. Re- 
garding this, we may lay dowm the principle, 
that it is so much the more diminished in ve- 
getable and animals, as those bodies are least 
distant from their origin, or from the periods 
of their development and growth, whilst it 
increases, together with the rigidity, in pro- 
portion as they approach the end of their 
career. 
In organic bodies, on the contrary, which 
are composed entirely of solid parts, are re- 
markable for their great regidity. In them 
we do not see parts differing in point of con- 
sistence, neither does their rigidity vary with 
the duration of their existence. 
XXXI. Another consequence ofthernix- 
ture of the solids and fluids, which enter into 
the composition of living bodies, as well as of 
their state of softness, is the facility with which 
they undergo changes in the relations of their 
structure, that is, with which they move. 
These two very circumstances render their 
chemical composition more easily attacked 
by external influences, as of heat and the 
atmosphere, which act principally on their 
liquid parts. Minerals, which are composed 
of solids, and possess rigidity, do not exhibit 
these changes in the mutual connexion of 
their parts ; that is to say, they do not move 
• The drops of water which are met with 
sometimes in crystals can scarcely be brought 
forward as an objection, because they are purely 
accidental. Thus Brewster (Transactions of the 
Royal Society of Edinburgh, vol. x. p. 1,) found 
colourless and transparent liquids in some to- 
pazes, in the chyrsoberyl, in the Quebec quarz, 
in the amethyst, &c. Commonly these liquids 
only in part filled the cavities of the crystals, 
and besides contained a bubble of air, which dis- 
appeared by the action of heat. Neither can 
the water of crystallization be objected, since it 
is intimately combined with the very matter of 
the crystals, and is not distributed in specified 
spaces, as the humours of living bodies are. 
and are less liable to be varied in their com- 
position by the action of exterior influences, 
particularly of heat and the atmosphere. 
XXXII. All organic bodies do not only 
exist as a result of an assemblage of solid and 
liquid parts, but moreover this sort of consti- 
tution is indispensably necessary to their ex- 
istence and preservation, inasmuch as it is tlie 
reaction of solid and liquid parts which de- 
termines and maintains the manifestations of 
activity or of life-* If the juices of a plant 
are abstracted, it dies; if the mass of its 
humours are withdrawn from an animal, and 
its vessels emptied of the blood contained in 
them, life is extinguished. Let the solid parts 
be destroyed in a mechanical or chemical 
manner, in this case too the manifestations 
of the life cease. It follows, then, that the 
solids and liquids of living bodies are in a con- 
tinual reciprocity of action, indispensably ne- 
cessary to the support of life. 
XXXIII. Another cause, too, of the essen- 
tial and necessary connexion which exists, 
in organized bodies, between the liquid and 
solid parts, is that the latter take their origin 
from the former. Every animal originates 
from a liquid, in the midst of which it is form- 
ed. Liquids, also, are inces-antly furnishing 
the materials for the nutrition of the solids. 
'J'hese possess capability of exercising their 
manifestations of activity only so long as tliey 
are nourished. Every substance whatever 
which enters into organic bodies, under the 
name of food, should be liquid, or at least 
susceptible of becoming so. The solid, 
themselves are likewise resolved into liquids, 
in short, all matters which are elicited and 
rejected from living bodies, during life, are 
more or less liquid. But the constitution of 
the liquids depend;?, in its turn, on the mani- 
festations of activity of the solids, for these 
are the chief source of the qualities which 
distinguish them. 
XXXIV. Neither is it difficult to convince 
ourselves, by an attentive examination with 
the microscope, that the parts entering into 
the composition of organic bodies, are of 
another nature from those which constitute 
minerals. By this instrument we perceive, 
both in the liquids and solids of vegetables 
and animials, globular or oval, and occasion- 
ally flattened, bodies. The most simple 
animals, such as the infusoria, polypi, as well 
as the most simjjle plants, the confervae, tie 
mellae, the pulverulent mushrooms, the 
bys.sus, &c., are composed of globules, as is 
* Some vegetables and animals, of the most 
simple species however, for instance, mosses, 
infusoria, ratifera, (vorticella rotatoria) vihri 
ones, (vibrio anguilla) tkc., survive for some 
time the loss of their liquid parts ; tliey may be 
dissected so as to give no sign of life, and when 
afterwards they are moistened, the phenomena 
of life are again roused in them, as is shown by 
the experiments of Needham, (Nouvelles de- 
couvertes faites avec le Microscope. Leyden 
1744,) of Baker, (Employment for the Micros- 
cope, London, 1764.) of Spallanzani, (Observa 
tions sur les Animaux qu’on peut tuer et res 
susciter a son gr6 ; in Opuscules de Physique, 
vol. ii, p. 261,) and of Foutana, (Sur le veniu de 
la vip^re, vol i.) 
