Abstract
The proper construction of the unit applied to the blood vessel is fundamental to the success of the thermostromuhr method of measuring flow of blood. Rein 1 developed the thermostromuhr and named the unit the diathermy thermo-element. This diathermy thermo-element is U-shaped and requires the use of collodion to hold it firmly on the blood vessel during an experiment. It is very satisfactory for short-time observations, but is less so for experiments in which the unit is to be kept on the blood vessel for several days.
Since it was obvious that a drop of collodion could not be expected to hold the unit to the blood vessel firmly enough to insure good electrical contact when the animal was allowed to run about, it was necessary to construct a unit better suited to such conditions. Consequently the unit described here was developed.
The dimensions of each particular unit depend on the size of the blood vessel to which it will be applied. Several units of varying sizes must be at one's disposal in order to permit the selection of the one which best fits the particular blood vessel. For a vessel the diameter of which is somewhat larger than 5 mm., the specifications for the transparent bakelite block are: length 19 mm., width 8 mm. and height 7 mm. The length of the block is determined by: (1) the distance from platinum electrode to thermojunction, which must be at least 1.2 times the diameter, that is, 6 mm. in this case; (2) platinum electrodes, which for this particular vessel are 4 by 4 mm., and (3) allowing 1.5 mm., at each end for suture holes.
The width and height are determined by the diameter of the hole into which the blood vessel is inserted (in this particular case 5 mm.), and by the thickness of wall necessary for sufficient rigidity and for countersinking the 4 leads.
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