A piece of thin gauze, or other light protective material, should be placed over the mouth of the tube, to prevent the entrance of foreign bodies. In cases where the operation has been performed for some temporary inflammatory closure of the air passage, retention of the tube for a few days may suffice. It may then be removed, but it must be remembered that the wound will generally close with great rapidity, so that it is as well to be quite sure of the patency of the natural passage before the artificial one is allowed to close by the removal of the tube. In cases where from long-standing disease or severe accident the larynx is rendered totally unfit for work, and the tube has to be worn during the rest of the patient's life, care must be taken (1.) lest the tube do not fit accurately, in which case it may ulcerate in various directions, even into the great vessels;[133] (2.) lest the tube become worn, and lest the part within the windpipe fall into the trachea and suffocate the patient.[134] LARYNGOTOMY.--As a temporary expedient in cases of great urgency, where proper instruments and assistants are not at hand, laryngotomy is occasionally useful, though from the want of space without encroaching on the cartilages of the larynx, and from its close proximity to the disease, laryngotomy is by no means a suitable or permanently successful operation. In the adult, especially in males with long spare necks, the operation itself is exceedingly easy to perform. The crico-thyroid space (Fig. XXXI. A) is so distinctly shown by the prominence of the thyroid cartilage, and is so superficial that it is quite easy to open it in the middle line with a common penknife, there being merely the skin and the crico-thyroid membrane to be cut through, with very rarely any vessel of any size. The opening can then be kept patent by a quill or a small piece of flat wood. This simple operation has in many cases, where a foreign body has filled up the box of the larynx, succeeded in saving life, and even in cases of disease I have known it useful in giving time for the subsequent performance of tracheotomy. Easy as it appears and really is, cases are on record in which the thyro-hyoid space has been opened instead of the crico-thyroid, such operations being of course perfectly useless. The incision is best made transversely. LARYNGO-TRACHEOTOMY.--This modification consists in opening the air passage by the division of the cricoid cartilage vertically in the middle line, along with one or two of the upper rings of the trachea. It seems to combine all the dangers with none of the advantages of the other methods of operating. It is close to the disease, involves cutting a cartilage of the larynx, and almost certain wounding of the isthmus of the thyroid; and it is not easy to see what corresponding advantages it has over tracheotomy in the usual position.