Nasal Nitrous Oxide Apparatus, Frankis Evans'

No.	Description		Cost
			£	s.	d.
187	Nasal Nitrous Oxide Apparatus, Frankis Evans’, with twin tubes from nose piece leading to control stopcock (as illustrated, fig. 185), 3 gal. red rubber gas bag and 3 feet pressure tubing (exclusive of cylinders)	each	5	4	6
188;	Ditto without control stopcock, gas bag or pressure tubing, but with mount for attaching to own gas stopcock and apparatus	each	3	17	6
Extract from the British Medical Journal April 18th., 1925 "Mr. Frankis Evans writes : The apparatus illustrated is a modification of Paterson’s nose piece for the administration of nitrous oxide. The nose piece is the same shape as the original, and has a wide and deep ruber pad. In my experience it fits noses of all shapes very well. The mouth piece is connected with the nose piece by a stout rubber tube, and can be swung round to the back. This movement cuts off the supply of gas to the mouth piece by closing a valve at the top of the nose piece. When not in use the mouth piece rests on the head-rest of the dental chair, and the whole apparatus is then held quite firmly to the nose by the weight of the gas bag hanging behind On the nose piece is an expiratory valve of the hairspring type which does not stick as the rubber flap type may. A rebreathing position is afforded by turning the tube carrying the expiratory valve through an angle of 45 degrees."

Note about prices:
British prices were in pounds (£ ), shillings (s.) and pence (d.). Each shilling is 1/20th of a pound, and each penny is 1/12 of a shilling or 1/240th of a pound. To convert to pounds, count each shilling as 0.05 pounds and each penny as 0.00417 pounds. Three pounds, twelve shillings and six pence is therefore 3.625 pounds.
In July 1996 one pound was worth 2.12 Canadian or 1.55 US dollars.