chap, ix.] THE NECK. 155 



notch varies greatly, and depends upon the length of 

 the neck, the age of the patient, and the position of 

 the head. If 2 inches of trachea are exposed above 

 the sternum when the head rests easily upon the 

 spine, then in full extension of the head some \ of 

 an inch more of the windpipe will, as it were, be 

 drawn up into the neck. According to Tillaux, the 

 average full distance between the cricoid cartilage and 

 the sternum is, in the adult, about 2^ inches (7 cm.). 

 The full distance in a child between three and five 

 years is about 1 inches (4 cm.), in a child between 

 six and seven about 2 inches (5 cm.), and in children 

 between eight and ten years about 2^ inches (6 cm.). 

 As may be imagined, the dimensions of the trachea 

 on section vary greatly at different ages, and even in 

 different individuals of the same age. This leads to 

 the question as to the proper diameter of tracheotomy 

 tubes. Guersant, who has paid much attention to 

 this matter, says that the diameter of the tubes should 

 run from 6 mm. to 15 mm.* The tubes with a 

 diameter of from 12 mm. to 15 mm. are for adults. 

 The tubes below 12 mm. are for children, and are 

 divided into four sets. 



No. 2. 8 mm. 4 to 8 



No. 3. 10mm. 8 to 12 



No. 4. 12mm. 12 to 15 



In children under eighteen months the diameter of 

 the tube should be about 4 mm. 



In performing tracheotomy it is most important that 

 the head be thrown as far back as possible, and that 

 the chin be kept strictly in a line with the sternal 

 notch, so that the relations of the middle line of the 

 neck be preserved. Full extension of the head not 



* The reader may be reminded that 12 mm. = about half n.a 

 inch, and mm., therefore, = about a quarter of an inch. 



