opinion he has for some time held that when hogs are once immunized against hog cholera but little need be feared from so-called "swine plague."

DESCRIPTION OF TESTS.

As already stated, the field tests covered a considerable area of territory and included the treatment of purebred hogs of different breeds, kept under the most favorable conditions, as well as herds kept under the prevailing farm conditions. In the section where the experiments were made swine raising is a very important industry and every farmer raises a considerable number of hogs every year notwithstanding the fact that hog cholera may have thinned out his herd the previous year, the number of breeding animals being maintained by purchase if necessary. The almost universal custom of raising hogs, together with the fact that the hog pastures on different farms are often adjacent, tends to favor the spread of hog cholera when it has once started in a neighborhood.

In Story County, Iowa, and the adjoining counties the hog-cholera record for 1907 is similar to that of many previous years. The disease began quite early in the summer in a few localities and gradually spread until before the close of the season a large extent of territory was involved. The demand for vaccination was very great and only a small number of the farms whose proprietors requested treatment could be visited.

MORTALITY IN UNTREATED HERDS.

While the high mortality among the untreated checks in the herds visited tends to show that the disease encountered was extremely virulent, the outcome in a few untreated herds located in the vicinity of those treated may also prove interesting. A farmer living in the suburbs of Nevada, Iowa, whose herd consisted of 205 hogs of different ages at the time the disease appeared in that vicinity in August, lost all but 3 old sows and 8 shotes. In a herd of 30 head located across the highway from treated herd No. 6, 22 died. A neighbor of the owner of treated herd No. 5 had 35 shotes and lost all but 6. In the same neighborhood in a herd of 37 hogs all died but 3. In the neighborhood of treated herd No. 45 one owner of over 100 head lost the entire number. Another lost 33 out of a herd of 36, and still another lost something over 50 per cent of his herd. The owner of treated herd No. 1 before the experiment was started on his farm had lost something over 90 per cent of his herd. In Boone County, Iowa, in the neighborhood of treated herd No. 29 a farmer having 24 head at the time the disease appeared lost 20.

The records of the untreated herds just given show a virulent type of disease, and autopsies on dead animals in untreated herds and on untreated checks in treated herds showed the characteristic lesions of hog cholera.

RECORDS OF HERDS TREATED.

HERD NO. 1.

Herd No. 1 was located in the northwest quarter of section 9, Nevada Township, Story County, Iowa. At the time it was first visited the owner had lost 90 head out of a total of 100, or very nearly his entire herd. The symptoms and lesions were those usually seen in hog cholera. Arrangements were made with the owner to carry out a test of the serum on his farm. For the test 13 small shotes, weighing from 35 to 40 pounds each, were purchased. These had not been previously exposed to hog cholera. Ten were injected with 20 c. c. each of mixed serum No. 1, and the remaining 3 were left untreated to serve as checks. The entire number were then confined in the hog house together with some of the sick shotes from the original farm herd. The experiment was started September 9, and ten days later the checks showed indications of disease. When seen on September 25 one of the checks was dead and the other two were very sick, with the usual cholera symptoms. On September 30 all of the checks were dead. All of the treated pigs continued well except one, which showed slight soreness of the eyes. Later observations showed that the treated pigs were well and thrifty. The result of this experiment became widely known in the surrounding country and led to many demands for the treatment of affected herds.

HERD NO. 2.

Herd No. 2 was located on the opposite side of the road from Herd No. 1, and consisted of an old sow and her litter of 5 shotes weighing about 75 pounds each. These animals, although close to infected premises, had remained well. The owner was present when the experiment with Herd No. 1 was carried out, and thinking that his pigs were in danger of infection, desired to have them treated. Three of the pigs were accordingly injected with 20 c. c. each of mixed serum No. 1 together with 2 c. c. of virulent blood. The other two were left untreated as checks.

As both the checks and the treated pigs remained well, we must conclude that exposure did not occur in this instance. The experiment is of interest, however, as it shows that three 75-pound pigs remained well after receiving the serum-simultaneous treatment, and that these pigs did not communicate disease to the untreated pigs which associated with them.

HERD NO. 3.

Herd No. 3 was located one mile east of Herd No. 1 and probably became infected through the extension of the disease from that herd. When the herd was first visited on September 14, 1907, two old sows

had died and a number of late-summer pigs were showing symptoms of the disease. Some of the spring pigs also seemed somewhat affected. The sick pigs showed the usual hog-cholera symptoms, including diarrhea. An autopsy on an old sow which had just died revealed hog-cholera lesions. Untreated checks which died after the experiment was begun also showed the usual symptoms and lesions of hog cholera.

Fifty-one of the spring shotes weighing from 30 to 50 pounds each were selected for the test. Two-thirds of the number, or 34, were injected with 20 c. c. each of mixed serum No. 2, and the remaining 17 were left untreated as checks. Two old sows and 1 large boar were treated with 40 c. c. each of the same serum. The sows had young litters which were not treated. The summer shotes and a few of the spring pigs were left untreated in addition to the 17 mentioned.

The results in this herd exceeded our expectations. Of the 34 treated shotes 6 sickened soon after treatment and died; some of these, however, were probably sick when treated. The other 28 continued well. Of the 17 checks but 2 survived, while all of the summer and spring pigs which were left untreated died. The boar sickened, but recovered. The 2 old sows did not sicken, but their young pigs all died. Had the entire 51 selected for the experiment been treated the loss in this portion of the herd would probably have been very small.

HERD NO. 4.

Herd No. 4 was located in the northwest quarter of section 11, Grant Township, Story County. When first seen on September 25, 1907, the herd was apparently well, although the disease had for some days been within half a mile of the farm. The herd consisted of 30 spring shotes, each weighing from 75 to 100 pounds, and 3 old sows with young litters.

In planning the experiment the intention was to treat all of the animals except the sucking pigs, but in collecting the spring shotes for treatment one escaped and could not be treated. Consequently 29 shotes and 3 old sows were treated, the shote which escaped and the sucking pigs being left as checks. The shotes each received 20 c. c. of serum No. 2, plus 2 c. c. of virulent blood, and the old sows were given 40 c. c. each of serum, plus 2 c. c. of virulent blood. The herd was treated on September 25.

On the following day one of the treated shotes appeared somewhat droopy, and two days later one of the old sows became sick, showing loss of appetite and other symptoms. The sow became worse and died nine days after treatment. The autopsy showed the usual hogcholera lesions-engorged spleen, congested liver, hemorrhages in kidneys, and well-marked ulceration of the cecum and colon. The droopy shote became worse and finally died. The check shote and

all of the sucking pigs also died. The other 28 shotes and the 2 old sows remained well and thrifty.

In this experiment we must conclude that the herd had been exposed to hog cholera before treatment, since repeated injections of virulent blood have shown that it would have been impossible for the serum-simultaneous treatment to have caused disease within one day after treatment. Therefore the shote which died was undoubtedly sick at the time of treatment. The experiment shows that large 100-pound shotes which received 20 c. c. of serum were able to withstand 2 c. c. of virulent blood administered at the same time.

HERD NO. 5.

Herd No. 5 was located in the southeast quarter of section 35, Grant Township, and was first seen on October 4, 1907. At this time one shote had died but the rest of the herd appeared healthy. An autopsy on the dead shote revealed the characteristic lesions of hog cholera-hemorrhages in the lungs and kidneys, engorged spleen, enlarged lymphatic glands, and ulceration of the cecum.

Thirty-nine spring shotes, weighing from 40 to 60 pounds each, were injected with 20 c. c. each of serum No. 2. Eight shotes of the same size were left untreated as checks. Five old sows received 40 c. c. each of the same serum; each of these sows had litters, the total number of sucking pigs being 30.

Four of the 8 check shotes sickened and died, and 2 others sickened but recovered from the disease although they remained in poor condition. Two of the treated pigs died and the other 37 remained well and thrifty. The old sows remained well, but all of the sucking pigs died but 4. When we consider the results with this herd it seems probable that the loss would have been very light had the entire herd been treated.

HERD NO. 6.

Herd No. 6 was located in the northeast quarter of section 3, Grant Township, and probably became infected from a diseased herd just across the road. When seen on October 5, 1907, one shote was reported as having been sick for three days; this animal appeared droopy and was not eating well. Another animal seemed a little. indisposed, but the remainder of the herd appeared well, All of the animals ran together in the same yard and pasture.

Twelve shotes, ranging in weight from 40 to 70 pounds and including 2 sick animals, were left untreated as checks. The remaining 67 animals received the serum-simultaneous treatment, each shote being given 20 c. c. of No. 2 serum, plus 2 c. c. of virulent blood.

Of the 12 untreated shotes 8 died after exhibiting the usual hogcholera symptoms; 2 others sickened and recovered, but remained in a

stunted condition. Of the 67 treated pigs but 3 died, the others remaining well and thrifty.

The heavy loss among the checks indicates that the disease was quite virulent, and the result of the treatment shows that in this instance at least the use of virulent blood in connection with the serum subsequent to exposure did no harm. Had the entire herd been treated the loss would in all probability have been very slight, and the experiment illustrates what can be done in many herds if the serum is used early.

HERD No. 7.

Herd No. 7 was located in the northwest quarter of section 27, Grant Township, and was first seen on October 7, 1907. The herd was found in bad condition. A number of the shotes showed unmistakable symptoms of hog cholera; they were droopy, did not eat well, and a few had diarrhea. Some of the animals had been sick for three or four days before the herd was visited, and 2 had died only a few hours before. An examination of the dead animals revealed well-marked hog-cholera lesions-enlarged inguinal glands, engorged spleen, hemorrhages in kidneys, cecal ulceration, etc. The shotes all ran together and consequently all had been well exposed to the disThe old sows, 14 in number, were kept in a separate lot and consequently were not so much exposed.

ease.

Twenty-nine pigs, many of them no doubt already slightly affected, were injected with 20 c. c. each of serum No. 2. Four apparently healthy pigs and 10 which showed signs of being indisposed were left as checks. Eleven of the old sows were given 30 c. c. each of serum No. 2, and the remaining 3 received the same dose of serum plus 1 c. c. of virulent blood. On October 23 these sows were turned into the lot with the sick shotes.

Of the treated pigs 12 survived and 17 died. Of the 14 checks 11 died and 3 survived, one of the latter being stunted in growth and worthless. All of the old sows survived without showing any indications of disease.

Although many of the treated pigs in this herd died, the result shows that even in a badly diseased herd the use of serum will save a certain percentage of the animals, probably enough to warrant its use.

HERD No. 8.

Herd No. 8 was located in the southeast quarter of section 1, Grant Township. The owner had lost most of his hogs from hog cholera and desired to test the effect of the serum treatment by having some susceptible pigs treated with the serum and then placed on his supposedly infected premises. Accordingly he pur