292 TiMEHRI. 



decline in numbers takes place, it being scarcely possible 

 to find a single specimen in blood drawn during the day- 

 time. And it is at night-time that the mosquito is best 

 enabled to perform its work of execution on human 

 beings. This appearance of the filaria at night-time 

 and their disappearance during the day, is known as 

 " Filarial Periodicity." 



The above parasites form typical examples of the 

 Entozoa common to British Guiana and other tropical 

 countries. Of the next division of the Zoo-parasites, 

 viz., the Eftozoa, it will be necessary for me to say 

 but little, including as it does so many too familiar, and 

 withal, loathsome creatures. But there is one parasite 

 amongst them peculiar to British Guiana and most 

 tropical countries about which, although very well- 

 known to all residents here, it may be interesting to say 

 a few words. I refer to the Chigoe (pronounced Jigger), 

 or to give it its full classical title, Pulex penetrans. 



It is a very minute parasitic inse6l usually regarded as 

 a true flea belonging to the genus Pulex. '' The Chigoe 

 ordinarily lives in dry and sandy situations, where it 

 multiplies to a prodigious extent. It attacks, however, 

 the feet, chiefly underneath the nails and between the 

 toes; the impregnated females burying themselves be- 

 neath the skin." But it is by no means limited to 

 the feet for its sojourn, I have seen several cases where 

 the hands and other parts of the body have been affefted, 

 chiefly amongst coolies working on estates. After it has 

 burrowed beneath the skin its abdomen swells to the 

 size of a pea or larger ; and, unless removed by opera- 

 tion, gives rise to acute local inflammation, terminating 

 in suppuration and sometimes in extensive ulceration. 



