A note on the anatomy of the pulmonary arteries of mammals

Pianal was the first to describe a discontinuous ar segmented musculature in the final ramifications of the pulmonary arteries (arterioles) of certain mammals. This condition is most pronounced in the ox. Here the tunica media consists of successive rings of smooth muscle connect.ed by thin interannular spiral bands of similar muscle2 (fig. 1). A like condition is said to obtain in the calf, pig, and sheep, but of very much lesser degree. In man, horse, cat, dog, and rabbit the pulmonary arteries are said to have the same structure as the arteries of other parts of the body, ie., their musculature is continuous. While engaged upon a microscopic study of the lung of the guinea-pig, with a view to discovering some anatomic bwis for the unique occurrence in this form of acute anaphylactic death, Schultz and Jordan3 discovered a very pronounced segmented condition of the musculature of the pulmonary arteries. While this condition, peculiar to guinea-pig as far as was then known, was recognized as a possible contributory factor in the production of the immediate anaphylactic reaction, certain anatomic conditions of the secondary and tertiary bronchi were regarded aa the primary factors. It seems probable, howevsr, that the