The method of propagation and collection of the virus is in general the same in all countries. The animals are young calves from two to six months old, sometimes cows. Heifer calves are preferable on account of greater cleanliness of the vaccinated surface, although bull calves are frequently employed. Young camels, goats and water-buffalo calves are also used in some Ori ental countries. Calves are selected as for their soundness and kept under observation for a few days, when they are cleansed by a bath of soap and warm water. Just before their vaccination an area of the skin, usually extending over the whole of the abdominal surface, is carefully shaven, cleansed again with soap and water, and then with sterilized water. Some operators apply some antiseptic, like trikresol, carbolic acid or corrosive sublimate, in disinfecting the skin, removing this with copious quantities of sterilized water. The shaven surface is then dried, and shallow incisions, 'just cutting through the outer layer of the skin (not drawing blood) are made with some sharp instrument. The in cisions are made in long lines, or interrupted, so as to leave more or less healthy skin between them. The vaccine virus is then applied to these incisions and thoroughly rubbed in. The vaccine lesions begin to show on the second and third day, reaching full development between the fifth or sixth day. The most perfect method now in existence of propagating and collecting bovine vaccine virus is that employed by the Japanesegovernment. Nearly all the virus sup plied in Europe, Japan and the United States has glycerine added to it in different proportions for preserving it, as well as to eliminate the extraneous bacteria. Some is furnished in the dried form, especially in the United States, hut the bulk of it is glycerinized. In nearly all European countries the production of vaccine virus is under state control, although there are many private establishments which also furnish it. Germany has 25 state vaccine stations, Hol land 11, Denmark 1, England 1 and 9 or 10 private establishments, Sweden 1, France sev eral private, Japan 2. In the United States there are 10 stations— three State and munic ipal and seven private. The State and municipal establishments are located as follows: Massa chusetts 1, New York City 1, North Carolina 1. The private establishments are Pennsylvania 2, New York 1, Michigan 1, Indiana 1, District of Columbia 1, California 1. When com pared with the distribution of these establish ments in European countries, it will be seen at once that those in the United States are neither so numerous nor so advantageously located for supplying a virus to areas of equal extent, nor to the same number of population. In the former each vaccine establishment is supposed to supply virus to a certain territory, which is small as compared to the latter, and, moreover, the most important feature of such is that it is possible to supply a fresh virus quickly without the risk of deterioration incident to tempera ture and transportation over long distances.
Bacteria in Vaccine.— The many investiga tions made of the bacteria found in both the humanized and bovine virus are almost con clusive that they are in no wise connected with the specific cause of vaccinia. ALL vaccine virus contains many varieties of bacteria, some of these may be pathogenic, but the majority are harm less. Their origin may be from several sources from an antecedent virus, from the skin, from the alimentary tract of the vaccinated animal and from external contamination. Bovine virus usually contains the pus organisms, the staphylo coccus aureus and albus, the streptococcus and in rare instances the tetanus bacillus. A vac cine virus may contain a great number of bac teria and yet be harmless; on the other hand only a few of the pathogenic varieties, and may cause serious consequences. As a rule the number of bacteria may be taken as an index of impurity resulting either from a faulty preparation, or not subjected long enough to the action of the glycerine. Any treatment to which the vaccine tissues are subjected, with a view to freeing it from the extraneous bacteria, influences its potency to a more or less degree. If glycerine be added, the number will gradually diminish. So in order to obtain the best results it usually follows that there arrives a time when such virus is free of bacteria, or nearly so, and when its potency is very little impaired. The Japanese have discovered that vaccine virus to which glycerine has been added, can he made to withstand considerable quantities of pure carbolic acid and in such strength as to kill the extraneous bacteria, and to do so with out materially impairing its potency. Further, the vaccine virus can be produced bacteria free in certain animals, such as the male rabbit and calves, as has been suggested by Noguchi, but as yet this is in the experimental stage.
The preservation of the virus in a highly potent state is all important, it is quite sensitive to heat ; the hot weather of the summer months causes it to deteriorate rapidly. Low tem peratures on the other hand preserve it, and particularly is this so if the temperature is be low the freezing point. Elgin of this country was first to discover this fact, which was con firmed by Green of England. Vaccine virus when subjected to very low temperatures and maintained thus with but little variation will remain potent for months, even as much as two years.
Vaccination.— The slight injury to the skin, necessary in inoculating with the vaccine virus, appears on first sight to be of such a trivial character that it is not always treated with the regard which is due it. Vaccination is, in the strictest sense, a surgical operation. No one at the present time would be willing to undergo a surgical operation, it matters not how slight it might be, unless he was convinced that it would be performed skilfully, and that all neces sary precautions would be taken to insure its success. Vaccination is no exception, and due regard both for a successful inoculation and avoidance of complications must be kept in view. The following important points are to he considered: The condition under which the wound is made; the person vaccinated; the state of health; the peculiarity of temperament, and the conditions after vaccination. The inoculation can be made in any part of the skin, the site most preferable is on the outside and middle part of the arm just over the insertion of the deltoid muscle. The site selected for vaccination should at first be thoroughly cleansed with soap and warm water, then rinsed well with clean water, followed by the application of an antiseptic solution (1 per cent carbolic acid). The skin is then allowed to dry. When this is completed the site is ready for inocula tion. Small scarifications of not more than one-fourth inch square are made with some sharp, sterile instrument, for example, a lancer or needle, to remove the outer layer of the skin, care being taken during the process not to make the scarification too deep. Blood should never be drawn. The vaccine is then gently rubbed into the wound and allowed to become thoroughly dry. It is not advisable to protect the wound with any dressing or sub stance which might adhere to it, as this is one of the most fruitful sources of septic infection; Nature has already furnished the wound with a covering which, if kept intact, will answer bet ter than any artificial substance. The vacci nated places should be carefully protected against irritation, especially so when the lesion begins to assume the vesicular stage. It is then of the utmost importance to prevent its being injured. If, however, the vesicle is broken and there ensue severe local and constitutional symptoms, it is of importance that it be given surgical treatment. With a pure virus, vaccina tion, if carefully performed and given thorough attention after treatment, is practically without danger. Vaccination is sometimes followed with complications, the lesion being infected with pus organisms, giving rise to local abscesses; also septicamia, pyiemia, erysipelas, gangrene and tetanus are occasionally observed. These may be conveyed by a contaminated virus, but are usually from the vaccination being improperly performed or from neglect of the wound. It has been estimated that as much as 70 per cent of the septic mischief is due to the injury of the vesicle taking place during the first and second week, the unsanitary surroundings or dirty habits of the patient largely contributing to complications. That these instances are of rare occurrence is borne out by the reports from the Imperial Health Office of Germany, which show that among 32,166,619 vaccinations of children there have been 115 deaths, 67 of these being in some way connected with the operation of vaccination. This gives a rate of a little over two per million, as compared with the thousands who die from smallpox. Some times a general vaccinia results. The eruption is to all appearances the same as the initial lesion, and runs a similar course. In addition to this there are post vaccinal eruptions, ap pearing from 10 to 14 days after. These may be a simple rash, a bullous eruption resembling pemphigns, impetigo, eczema and purpura. While these have no direct relation to vaccinia, their occurrence at this time is thought to be due to the vaccinia being the exciting and not the predisposing cause.