In young animals of trifling weight immobilisation may be attempted, the best method being the application of pitch plasters. If, on the other hand, the subject is heavy, there is so great a chance of displacement when lying down and rising, that such cases are usually sent to the butcher, or abandoned to chance. Relative recovery, sufficient to permit of growth or fattening, may take place without professional assistance.
IV.—HYGROMAS.
Hygromas result from chronic inflammation of serous bursæ, naturally existing, or of serous bursæ which form at prominent points where the skin is exposed to repeated friction, blows, shocks, or over-extension.
They usually develop slowly, without producing marked pain or alarming symptoms, and therefore the practitioner is seldom consulted until the swelling has attained a considerable size.
The hygroma is usually characterised by its non-painful character and by regular fluctuation throughout. The walls of the serous bursæ are merely thickened, so that palpation is easy.
Should the hygroma become infected and inflamed, it assumes the same characters as an abscess: it becomes highly sensitive, is surrounded by œdematous infiltration, shows more marked fluctuation at some specialised point, and eventually breaks, discharging pus.
Long-standing hygromas often have thickened fibro-cartilaginous and extremely hard walls, which render examination more difficult.
Fig. 25.—Old-standing hygroma of the knee. PE, external coat; CC, cornified coat; CO, osseous coat; CP, pus cavity; PI, internal coat.
Where the hygroma is much exposed to friction the skin covering it undergoes complete transformation, the layers of epidermis becoming converted into a substance resembling horn. The entire substance of the wall of the hygroma then undergoes change, and is often infiltrated with lime salts or encrusted with plates of bone of varying thickness.