548 ME CHANISM OF SE CRE TION OF PANCREA TIC JUICE. 
centre for pancreatic secretion, as, after its separation from the cervical 
spinal cord, the secretory process can continue, although with diminished 
intensity. 
4. The nerves proceeding to the pancreas do not seem to have the 
same direct influence upon the secretion that the nerves to the salivary 
glands possess. 
5. Stimulation of the central end of the divided vagus, according to 
Bernstein, 1 or of sensory nerves in general (e.g. cutaneous), according to 
Afanassiew and Pawlow, 2 may inhibit the secretion, provided the pan- 
creatic nerves are intact. This, Heidenhain regards as due to vascular 
changes. 
Pawlow 3 found that the administration of atropine stopped the 
secretion frequently, but not in all animals (e.g. in dogs but not in 
rabbits), and Heidenhain observed that the administration of pilocarpine 
caused a sluggish secretion of a concentrated juice. 
The later experiments of Pawlow and the St. Petersburg school have 
greatly amplified our knowledge of the nervous influence. In Pawlow's 
further researches he observed the effects of nerve stimulation upon dogs 
prepared for experiment in two different ways. In the first case the 
dog had a permanent pancreatic fistula prepared, one vagus in the neck 
was also divided. The stimulation of the peripheral stump of the vagus 
was performed some five days after the section, at a time when certain 
fibres in the vagus had degenerated. In the second case the vagus was 
cut through in the neck, and after three or four days the animal was 
prepared for experiment by the performance of tracheotomy, section of 
the spinal cord just below the medulla oblongata, and the preparation of 
a fresh pancreatic fistula. In both these cases stimulation of the peri- 
pheral end of the vagus causes secretion from the pancreas. Moreover, 
stimulation of the intact vagus also produces this result, and even if 
neither vagus is divided a more or less pronounced secretion ensues. 
Certain differences are observable, however, between the general effects in 
the two cases. In the first case more secretion was produced, this being 
comparatively watery in character and greatest in amount at the 
commencement of stimulation. These differences are probably accounted 
for by the general low blood pressure in the second case. The pressure 
of the secretion was found by Pawlow to be lower than the corresponding 
blood pressure, and it was noted that vagus stimulation in one case still 
caused a secretion, although the blood pressure was reduced by bleeding 
practically to nil. Frequently the secretion would end with the lowering 
of the blood pressure, but nevertheless the one experiment is sufficient 
to establish the independence of the secretion of the blood pressure. 
The action of atropine is to cause a marked influence on the effects 
of nerve stimulation, though complete cessation of the secretion is not 
produced. Keflex effects can be produced on the secretion, which do not 
correspond to the effects upon the blood vessels. Stimulation of the 
central stump of the lingual or of the vagus nerve will produce such reflex 
effects. If, at the commencement of the experiment, either no secretion 
or a slight secretion occurs, with the first stimulation of sensory nerves 
either a commencement or an increase of the secretion results. After 
the stimulation ceases this lessens. If after the first stimulation the 
1 Ber. d. h. sacks. Gesellsch. d. Wissensch. , Leipzig, 1869. 
2 Arch. f. d. ges. Physiol., Bonn, 1878, Bd. xvi. 
3 Arch./. Physiol., Leipzig, 1893, Supp. Bd. 
