Differences in Spread of Dye in Skin of Normal and Tuberculous Guinea Pigs

Abstract

In a study of the skin of guinea pigs, it has been found that the tuberculous animal reacts differently from the normal in regard to the spread of dye which has been injected intradermally.

We have made tests to see if differences could be detected in the spread of dye in the skin around the zone of primary inoculation as contrasted with other areas. The work was started in the course of completing a study of the Koch phenomenon which had been begun by the late Henry Sewall. He had obtained evidence that there are differences in sensitivity in different areas of the skin of the tuberculous guinea pig.

The dye used was pontamine sky blue which we obtained through the courtesy of Dr. P. D. McMaster, and in general we have followed his technique. 1 We have used the dye as a 2.5%, approximately isotonic solution. The amount of solution injected was 0.025 cc, given with a Dewitt and Herz syringe which has an automatic guard on the plunger, assuring exact dosage. The injections were made under a binocular dissecting microscope under brilliant light, the animal having been anesthetized with sodium amytal.

It was found that there are some differences in the rate of spread of dye, according to varying thickness of the dermis. In the guinea pig the thickness of the dermis in dorsal, lateral, and ventral zones is in the proportion of 2:l.S :1, that is to say, the skin on the back is twice as thick as that on the aldonien. Hence, to be comparable, injections must Ix restricted to one of these 3 zones. Usually 3 injections. 2 on each sidewere made in each animal but in the case of some of the dorsal injections, only 2 were made, each in the mid-line. IVhen the injections Ivere thus limited, the spread in a given animal 11 as practically identical. provided that in the tuberculous animal the indurated Imrder of the primary ulcer was avoided.