determining their peculiar distribution. Their absence from the liver and spleen is a remarkable fact.
Since this was written they have been found in the spleen tissue by other observers. The capillaries of the lung appear to be the favourite habitat of microfilariæ. Microfilaria immitis, mf. perstans, and the non-periodic Fijian microfilariæ have been found in greatest abundance in this situation.
Non-periodic microfilaria bancrofti.—Until recently it was believed that, in natural conditions of health and habit on the part of the human
Fig. 100.—Section of lung showing microfilariæ in the blood-vessels.
(From a microphotograph by Mr. Spitta.)
host, nocturnal periodicity was uniformly observed by the microfilaria of Filaria bancrofti at all times and in any country. Many years ago Thorpe remarked that in Tonga and Fiji the filaria could be found often in great abundance in the blood during the daytime; and in 1906 Ashburn and Craig found a microfilaria in the Philippines which showed no periodicity, and which these authors, relying on this feature, considered a distinct species and named
