The above quotations

sum up pretty well the statements of all
previous writers. Furthermore, there are some writers on Natural
History who have not ventured to lay down the law in such precise
terms as regards the veins, but who all alike agree in assigning the
head and the brain as the starting-point of the veins. And in this
opinion they are mistaken.

The investigation of such a subject, as has been remarked, is one
fraught with difficulties; but, if any one be keenly interested in the
matter, his best plan will be to allow his animals to starve to
emaciation, then to strangle them on a sudden, and thereupon to
prosecute his investigations.