animal. It is possible to find the parasites in the mane. and tail of apparently healthy animals during summer. It is these animals which break out with the disease if clipping is not done or there is neglect in grooming in the winter. The disease, being easier to cure than the sarcoptic form, has decreased in prevalence under legislative control.

In cattle it often starts at the base of the tail, spreads slowly, and frequently disappears when warm weather sets in. This fact has been noted in a number of manges, and explains the different results obtained with various treatments at different seasons of the year.

In sheep scab the early lesion is masked by the fleece, but clinical symptoms are soon shown. The delicate skin, when inspected, has clear lesions with parasites at work. What has been said with regard to finding Sarcoptes equi applies also to the psoropt. In early cases, with the aid of a lens, the parasite can often be seen at work at the edges of the lesion; and if a little of the accumulated "scab " from the edge of an affected part be warmed in the closed hand, the mites can usually be discovered running about with the unaided eye. Warmth makes them very active, and a piece of blackened glass may be heated over the spirit-lamp and the suspected material placed upon it. After soaking in a 10 per cent. solution of caustic potash and then being examined between two slides under the 3-inch lens material from the edge of an active lesion should reveal the parasites. Failing these methods, boiling in 10 percent. caustic potash solution and centrifuging will have to be carried out.

FIG. 21.-PSOROPTES EQUI. (After Newstead and Morris.)
1. Female, ventral aspect. X 117.

2. Male, ventral aspect.

X 117.

3. Tarsus of leg II. of female, side view. X 250.

4. Egg. X 117.

Reproduced by permission from Report No. 8 of the Grain Pest (War) Committee

of the Royal Society.

In general terms the treatment of psoroptic mange in equines is the same as for sarcoptic scabies. Minute attention to (1) complete close clipping, (2) whole and thorough washing to remove all crusts, and (3) completely dressing all over are essential. Properly done, two complete courses of treatment are often sufficient because the parasite is on the surface of the skin. Reclipping and following up are important. A number of watery preparations used for, and at the same intervals as for, sheep scab are satisfactory, although the coat may be left somewhat harsh in appearance. The ear forms of psoroptic mange are usually amenable to careful cleansing and dressing in an oleo-sulphur liniment, but the sequelæ, such as damage to the lining of the canal, may have to have glycerin of iodine applied. Damage to the internal ear is very intractable.

Sheep-dipping is carried out in a great number of ways. It may be by a simple hand bath with a proprietary dip or by means of an elaborate plant for the preparation of the material and heating the dip. The commonest type of bath is the swim bath. It may be 33 feet long at the top, 20 feet 6 inches long at the bottom. The entrance end is vertically 3 feet 6 inches to 5 feet deep; the exit end thus slopes from top to bottom and is provided with footholds. The sides slope inwards, the width at the top being about 2 feet and at the bottom 9 inches.

The chief requirements of a dipping material are that it will kill the parasite, be non-toxic to animals and men, shall not damage the skin or fleece, shall not cause “set back,” shall be easily prepared, and shall be as foolproof as possible. Two dippings at an interval of from seven to twelve days should effect a cure; shearing should if possible be carried out a fortnight before dipping. Care must be exercised with rams and pregnant ewes.

After dipping animals should drain on a bare lot; warm dips are better than cold ones.

One has only to ask the question, Where does the arsenic go when the dip is drained? to see the wisdom of using non-toxic substances, let alone the chances of the immediate dangers of poisoning. The following are three dips approved of by the Ministry of Agriculture and Fisheries for 100 gallons of solution:

(a) Lime and Sulphur.-Mix 25 pounds of flowers of sulphur with 12 pounds of good quicklime. Triturate the mixture with water until a smooth cream without lumps is obtained. Transfer this to a boiler capable of boiling 20 gallons, bring the volume of the cream to 20 gallons by the addition of water, boil and stir during half an hour. The liquid should now be of a dark red colour; if yellowish, continue the boiling until the dark red colour is obtained, keeping the volume at 20 gallons. After the liquid has cooled, decant it from any small quantity of insoluble residue, and make up the volume to 100 gallons with water.

(b) Carbolic Acid and Soft Soap.-Dissolve 5 pounds of good soft soap with gentle warming in 3 quarts of liquid carbolic acid (containing not less than 97 per cent. of real tar acid). Mix the liquid with enough water to make 100 gallons.

(c) Tobacco and Sulphur.-Steep 35 pounds of finely ground tobacco (offal tobacco) in 21 gallons of water for four days. Strain off the liquid, and remove the last portions of the extract by pressing the residual tobacco. Mix the whole extract, and to it add 10 pounds of flowers of sulphur. Stir the mixture well to secure an even admixture, and make up the total bulk to 100 gallons with water.

The period of immersion in these dips should not be less than half a minute.

CHAPTER IV

SARCOPTIDE (concluded)

Genus Chorioptes Gervais 1859.

Syn.: Symbiotes Gerlach 1857. Dermatophagus Furstenberg 1861.

ANAL suckers in the male; copulatory tubercles in the female; ambulacral suckers carried on a very short pedicle on all legs of the male, and on the first, second,

Male, ventral aspect.

FIG. 22.-CHORIOPTES EQUI. X 120. (The fourth pair of legs and their suckers are indistinct, and the sucker of one third leg is not visible.)