Nearly every one who has had much experience in medical laboratories is aware of the difficulties frequently encountered in immobilizing various kinds of animals used in experimental work. Many types of animal boards, or holders, ranging from the simple piece of board with a nail and string in each corner to high priced manufactured articles, are in use for this purpose. In general, these boards are usually satisfactory if the period of restraint is for a short time only and a certain amount of movement of the animal's torso is of no importance. If it is necessary, however, for the animal to be held for a matter of several hours and if almost complete immobility is wanted the usual animal boards leave much to be desired. Throughout a number of years the writer has at various times carried out numerous investigations on the transmission of diseases by means or arthropod vectors with various kinds of animals being used for experimental hosts.