ON THE SPINAL PARASYMPATHETIC. Fourth Article

¹ Medical Clinic of the Tokyo Imperial University

In the cervical and lumbar regions the fine medullated fibres of the dorsal root belong almost exclusively to the spinal parasympathetic system ; they amount to about 40 per cent. of all fibres of the root.

In the thoracic region one-third or one-half of the fine medullated fibres of the dorsal root belong to this system ; in the second sacral segment only one-fifth.

In the thirteenth thoracic segment the spinal parasympathetic fibres are exceptionally numerous.

The first sacral segment shows in some individuals the type of the second sacral, in others the type of the lumbar region.

In absolute number the spinal parasympathetic fibres show individual differences.

The fibres in question supply the blood-vessels of the viscera, viz. vasoconstrictors for the pulmonary vessels, and vasodilators for those of the stomach, intestine, kidney, suprarenal capsule, and testicle. They carry motor impulses to the muscular coat of the stomach and intestines.

The number of spinal parasympathetic cells in the cord runs parallel with that of spinal parasympathetic fibres.

The spinal parasympathetic system is most developed in the cervical and lumbar enlargements.

The spinal parasympathetic fibres carry impulses to the sweat glands, skin-vessels, and pilomotor muscles, and also to skeletal muscles, bones, and joints. This is illustrated by the study of cases of tabes, syringomyelia, and leprosy.