HISTORY AND HABITS OF THE TESTUDINATA. 
XV 
NATURAL HISTORY AND HABITS OF THE TESTUDINA 
The habits of Tortoises appear at first sight to offer but scanty materials for the 
observation of the student of Nature, or the records of her historian. It would 
however be indeed an anomaly in natural history, were this tribe of animals 
to exhibit nothing in their manner of life which should interest the zoologist 
—no illustrations of creative design in their structure, no remarkable instances 
of instinct in their habits, nothing in the phaenomena of their organization to 
satisfy the researches of the physiologist. The more we become familiarized 
with their manners and mode of life, and the further our investigations are 
carried into the effects of external agents in modifying the natural circum¬ 
stances of their existence, the more we shall feel satisfied that even in these 
sluggish and cold-blooded creatures,-—the slowness of whose pace has become a 
proverb, and their inactive and torpid life a common illustration of the vices 
of idleness and sloth,—the law of all nature still holds good, that nothing has 
been formed in vain, and that the structure of every animal alike displays the 
wisdom and perfection of the great plan of creation, and the accurate adapta¬ 
tion of organs, at once to internal function and to external habits. 
A moment’s consideration of the organization of these animals will prepare 
us to look for and to understand some of the most remarkable and interesting 
of their habits. Partaking, with the rest of the Reptilia, in the imperfect 
nature of the respiratory and circulating systems, it results that the body is 
incapable of keeping up any standard degree of temperature, which changes 
therefore with every alteration of the surrounding atmosphere. They are in 
fact what are termed cold-blooded animals. The mutual relations which exist 
between any one function of the animal body and all the others,—the recipro¬ 
cal dependence of the functions of circulation, of respiration, of nervous activity 
and power, of digestion and secretion,—the intimate connexion, in short, by 
which all these functions are made to vary according to the variations of any 
one of them, receive the most striking and beautiful illustration in the habits 
of the Testudinata, as well as of all other forms of the Reptilia ; and at once 
account for and require all those peculiarities which distinguish them from 
other classes of animals. Deriving their animal heat, then, only from external 
