THE SECRETION OF THE COLON OF THE CAT

¹ Sir William Dunn School of Pathology, Oxford

1. Stimulation by faradic stimuli at the rate of thirty per second of the peripheral ends of the severed nervi erigentes of decerebrate cats causes a secretion of fluid by the colon. The distal half of the colon forms this fluid at an average rate of 5 c.c. per hour when stimulated for 25 seconds per minute.

2. Secretion by the colon can also be excited by stimulating the central end of one nervus erigens when the other is left intact.

3. The rate of secretion is reduced by stimulating the nerves emanating from the inferior mesenteric ganglia at the same time as the nervi erigentes.

4. Stimulation of these paravertebral sympathetic nerves alone does not excite any secretion by the colon.

5. The administration of eserine increases greatly the rate of secretion excited by nervous stimulation.

6. Narcotics, e.g., chloralose and luminal, greatly decrease the rate of secretion. This is a peripheral effect, for it occurs in the completely decentralised colon. The fact that it is combated to a large extent by eserine suggests that it is due to narcosis of the enteric plexuses.

7. A similar fluid is secreted in response to injection of pilocarpine and, in the eserinised cat, acetylcholine.

8. Atropin inhibits the secretion caused by any of these procedures.

9. The composition of the secretion is: Total inorganic . •95 per cent. Enterokinase Nil. Organic matter . •46>0 per cent. Invertase Nil. Chlorine . •34 per cent. Amylase Trace. Phosphate . •0·5 mg. per cent. Dipeptidase Present. Calcium . •2·0 mg. per cent. Erepsin Nil. Trypsin Nil. Lipase Nil.

10. The resting or atropinised colon can resorb this secretion completely.

11. The reaction of the fluid when collected is about pH 8•4, but rapidly goes to pH 9•1 when exposed to the air. 1 c.c. juice neutralises about 0•5 c.c. of N/10 HCl. The reaction of the solid fweces contained in the colon varies from pH 7 at the surface to as low as pH 4•8 at the centre of the mass.

We are indebted to the Nuffield Trust for a grant towards the expenses of this work.

Dr. E. Chain has been most helpful with assistance in the chemical estimations; Dr. Sanders kindly photographed the abdominal window, and Dr. C. L. G. Pratt supplied a good trypsin activator. H. Axtell and A. Sale have provided technical assistance.