What is the matter with Caroline, the cow with the crumpled horn?

I scanned this illustration from a 1929 book my father had as a little boy.

What is the matter with Caroline, the cow with the crumpled horn?
She mopes and moos from morn till night, and shrivers from night till morn.
The doctors from Elfland, far and near, have gathered to ease her pain;
They've tickled her nose, they've woggled her ear, and pummelled her back, in vain;
They've taken her pulse and her temperature, and they think it might be mumps,
           Measles perhaps, or whooping cough, or merely a fit of the dumps!