560 
THOMPSON YATES LABORATORIES REPORT 
no means proved. It may quite well have been due to handling the yellow fever patients, 
many of whom were affected. This is a point which can only be determined by 
careful watching in an individual who has never before been affected on a first visit 
to tropical regions. 
The lesions seen at the very earliest consist of a patch of inflammatory redden- 
ing with a tiny vesicle at its middle ; the vesicle enlarges, but generally remains quite 
small ; the contained fluid is at first clear, but later may become turbid and finally 
purulent if it persists and does not disappear. Where there has been local spreading 
a considerable area of skin may be reddened and scattered about upon it are 
numbers of the vesicles ; these are generally more minute than when a single 
isolated vesicle develops. In distribution they are between the hair follicles, and 
presumably are due to the involvement of the sweat glands. Occasionally, however, 
they may be close to the hair follicles, and these sometimes appear to get involved. 
Presumably, at the moment when the vesicle becomes tense, a sharp, intense sensa- 
tion is produced, and the inclination to rub or scratch is very great. Rubbing or 
scratching, however, rather tend to increase the irritation. After a time the local 
condition subsides spontaneously, but it may reappear at the same site on a future 
occasion ; meanwhile other areas are in the acute stage. 
Microscopic contents of the vesicles. With the aid of some squeezing and a very 
fine capillary tube, the contents of the vesicles can be removed and examined. When 
the vesicle is not too far advanced the fluid is clear, and is generally found to con- 
tain a few red blood corpuscles but no leucocytes ; at a later stage the leucocytes 
appear in greater or less numbers and give the purulent character. What attracts the 
attention at the early stage, before the advent of any or at any rate many leucocytes, 
is a number of small bodies endowed with active amoeboid movement. Their pro- 
toplasm is more refractile than that of the ' polynuclear ' leucocyte, and contains a 
small number of granules of a highly refringent character. The changes in shape 
of these amoeboid bodies are rapid without artificial heating of the slide at the 
ordinary afternoon temperature (2 7°-30° C), the pseudopodia being generally com- 
paratively blunt and rounded. The accompanying sketches shew some changes in 
shape, which occurred within the space of a minute or two (Plate VIII, Fig. 3). 
When the suppurative change has commenced large numbers of polynuclear 
leucocytes are to be seen, either entire or more or less disintegrated ; micrococci in 
pairs or in groups are also present in variable, generally small, numbers. Active 
amoebae, however, are then rarely found, but there are some globular bodies which 
would correspond in size to and which are possibly of the nature of encysted amoebae. 
The abundance of the amoeboid bodies at the earlier stages and the absence of 
micrococci or other bacteria at this time make it probable that the formation of the 
lesion is concerned with the presence of the amoebae, the later invasion and suppura- 
tion, when it occurs, being caused by the micrococci or other bacteria. 
