352 ANIMAL PHYSIOLOGY. 
that it must be regarded even in those parts that eliminate 
most water as a genuine secreting mechanism. 
We wish to present a somewhat truer conception of the 
lymph that is separated from the capillaries and bathes the 
tissues. 
We would regard its separation as a true secretion, and not 
a mere diffusion dependent wholly on blood-pressure. The 
mere ligature of a vein does not suffice to cause an excess of 
diffusion, but the vaso-motor nerves have been shown to be 
concerned. The effusions that result from pathological pro- 
cesses do not correspond with the lymph—that is, the nutrient 
material—provided by the capillaries for the tissues. These 
vessels are more than mere carriers; they are secretors—in a 
sense they are glands. We have seen that in the foetus they 
function both as respiratory and nutrient organs in the allan- 
tois and yelk-sac, and, in our opinion, they never wholly lose 
this function. 
The kind of lymph that bathes a tissue, we believe, depends 
on its nature and its condition at the time, so that, as we view 
tissue-lymph, it is not a mere effusion with which the tissues, 
for which it is provided, have nothing todo. The differences 
may be beyond our chemistry to determine, but to assume that 
all lymph poured out is alike is too crude a conception to meet. 
the facts of the case. Glands, too, it will be remembered, derive 
their materials, like all other tissues, not directly from the 
blood, but from the lymph. We believe that the cells of the 
capillaries, like all others, are influenced by the nervous system, 
notwithstanding that nerves have not been traced terminating 
in them. 
It is to be borne in mind that the lymph, like the blood, 
receives tissue waste-products—in fact, it is very important to 
realize that the lymph is, in the first instance, a sort of better 
blood—an improved, selected material, so far as any tissue is 
concerned, which becomes gradually deteriorated (see Fig. 329). 
We have not the space to give all the reasons on which the 
opinions expressed above are founded; but, if the student has 
become imbued with the principles that pervade this work thus 
far, he will be prepared for the attitude we have taken, and 
sympathize with our departures from the mechanical (physical) 
physiology. 
We think it would be a great gain for physiology if the use 
of the term “absorption,” as applied to the alimentary tract, 
were given up altogether, as it is sure to lead to the substitu- 
