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ELEMENTARY PHYSIOLOGY 



LAEYNX 



Thyroid . 

 Cricoid . 



Arytenoid 



Glottis . 

 Epiglottis 



Vocal cords 



SUMMARY. 



j The upper cartilage. 

 1 Wide in front ; open behind, 

 j A complete ring cf cartilage, 

 t Wide behind ; narrow in front. 



(Small pyramidal. 

 Surmount the upper posterior edge of the 

 ciicoid. 

 Jointed with the cricoid. 

 i The communication between the pharynx 

 I and the larynx. 



I Bounded on each side by the vocal cords, 

 i A thin movable layer of cartilage. 

 ] Closes the glottis during the act of swal- 

 * lowing. 

 Bands of elastic fibres. 

 Embedded in mucous membrane. 

 Relaxed during quiet breathing. 

 Stretched during speaking and singing. 

 Attached to arytenoid cartilages behind, 

 and to the thyroid in front. 



QUESTIONS ON LESSON XXXVII. 



1 . Describe the structure of the larynx. 



2. What are the vocal cords ? In what way do they assist in the production 



of the voice ? 



3. By what means are we enabled to sing notes of different pitch ? 



4. Describe the arrangement of the vocal cords. How do their positions vary 



(i) when we sing a note of high pitch, and (2) when we heave a deep 

 sigh? 



LESSON XXXVIII. 

 EPITHELIUM. 



IN Lessons XXIII. and XXIV. the word epithelium occurs. This 

 term is applied to the cellular tissue that, continuous with the 

 epidermis, lines the entire length of the digestive tube, as well as 

 the ducts of the glands which pour their secretions therein ; also 

 to the membranes that form the linings of the blood-vessels, 

 lymphatics, and serous cavities ; the respiratory passages ; the 

 sensory surfaces of the mouth, nose, eyes, and ears ; the cavities 

 of the brain : and the central canal of the spinal cord. 



In structure, epithelium consists of cells of various shapes, 

 sometimes arranged in a single layer (simple epithelium), and 



