The histological character of the primary cancers would place them in group of the nodular and infiltrative types of Kauffman. They all seem to have taken their origin from the smaller bronchi, the usual starting point. The growths were small in the civet and bandicoot and strongly suggest that the tumors arose in bronchi occupied by parasites; such bodies could not be demonstrated. It is the usual thing to find in cases of parasitism of the bronchi that if there be no ulcerative destruction of tissue the epithelium undergoes some form of hyperplasia, and even structural metaplasia in the air tubes supplied with cuboidal or cylindrical cells. Epithelia many layers deep have been encountered, usually arranged in orderly fashion but frequently “papillomatoid,” suggesting the epidermal layers yet not so far as to show protoplasmic bridges. Distention of various degrees, affected by the contents of the tube and the surrounding inflammation, are common. Such a picture naturally resembles epithelioma and indeed growths of this nature are reported as due to verminous pneumonitis. There are, especially in cats and dogs, small scattered adenomatoid growths[21] under the pleura and in the pulmonary substance, thought to originate in the alveolar epithelium and occasionally growing to large size; the case in the kangaroo may have had this origin. _It was the only primary tumor to give metastasis_ (to the spleen and gastric wall), the secondaries being decidedly adenomatous in character. Metastatic growths come from the following originals: two from the thyroid, well known to give pulmonary embolism in dogs; one each from the breast, uterus, adrenal, intestine and kidney. The form assumed is a gray and red mass lying under the pleura or an isolated nodule in the substance. Sarcomatosis, the form apparently spreading out from the hilum and growing in isolated grayish tubercular masses, has not been seen. THE PLEURA.