First Stage. Latent st age.
The effect of the specific infection with the vaccine virus is not visible at once. At first we notice but a slight change,the result of mechani cal irritation of the skin, " traumatic reaction." The site of vaccination, after a few minutes, appears red and on stretching the skin somewhat faded in the centre, as in urticaria, the prominence of the wheal depending on the sensitiveness of the skin.
In a few hours, we usually observe a redness of 3 to 4 min. in diameter, which disappears in the course of the day. On the following day there may be seen a small brown scab, surrounding which the skin may be slightly or not at all hyperaemic.
Second development of the vesicle. In two to four days, the specific process becomes visible.
Caroline L., aged five years, vaccinated on the 12th of January, 1907, in six different places on the left arm; two places showed no reac tion, the other four developed beautifully. The diameter of the local effect of vaccination measured at least once daily.
Explanation of the Curve.—Below is the body temperature, which at first was taken twice, later four times daily below the development of the local efflorescences. The curve of the papule is based on the aver age of the diameters of the four papules, the curve of the areola on the diameters of the total hypertemic zones.
The spot not infected for the purpose of control shows merely a small brown scab without any reaction surrounding it, there is seen at the points where vaccination has taken place a slight redness which in twenty-four hours is plainly raised as a papule above the skin surface. After another twenty-four hours, the differentiation between papule and aula is apparent.
The centre of the papule becomes conically ele vated and slightly faded, resembling normal skin in color, while the edges of t he papule become flat tened and ret ain t he bright red color.
Now a uniform growth of the papule be gins, increasing from day to clay, about 1 mm. While it is at first difficult to distinguish it from nor mal skin, it gradually as sumes the character of a small vesicle. On punc turing, there exudes very slowly a clear lymph, con taining abundant viru lent vaccine organisms which may be utilized for further vaccination. At one time this "Jen ner's vesicle" was used to obtain the humanized lymph.
The papule is not round but depressed in the centre (umbilicated), the edges appearing prominent and well-defined in the surrounding zone of redness, "the Aula." As the papule develops, it pushes out the red ring, although it does not get broader until the Third Stage.—The development of the Arcola.
The red border begins to spread, the whole surface becomes infil trated, appearing as a red plate of 40 to SO mm. diameter, bearing the papule. After two or three days, the middle zone of the areola begins to fade, the inner zone surrounding the papule becomes pigmented while the outer zone stands out as a red border, but disappears a day later. Then commences the Fourth Of the areola only the pigmentation remains, and a slight hyper xmia near the papule. During the development of the areola, the papule (owing to the invasion of leucocytes) assumes a yellowish-white color. The vesicle becomes a pustule or pock. Now it begins to dry, at first in the centre, spreading from day to day toward the periphery, while the growth of the pustule is arrested. It gradually dries up altogether, and the brown scab falls off after about ten days (20 to 2S days after vaccination), leaving the well-known vaccination scar.
If the pustule has been broken by scratching or becomes macerated by dressings, it usually takes longer for it to heal, undoubtedly because of secondary infection.
The body temperature in the first stage is not affected. There are slight elevations to 38° C. (100.5° F.) in the second stage. In the third stage, as a rule, fever is present from 38° C. (100.5° F.) to 39° C. (102° F.). This fever is a part of the vaccine infection. It does not depend upon any impurity of the virus, and can in no wise be prevented. Vaccina tion is not accompanied by temperature except occasionally in the new born and very amemic children. Among older and robust children it rarely runs its course without fever. The general condition is, as a rule, only in the third stage somewhat disturbed, corresponding with the height of temperature; there is malaise and pain in the infected arm, depending on the degree of local inflammation. As the vesicle is forming, the axillary lymph-glands become somewhat enlarged and a-re for a while palpable and slightly painful on pressure.