These symptoms are due to a continuance of the mucous flux from the alimentary canal which is always present to a greater or less degree in cases of pertussis. This copious alkaline secretion acts as a ferment and causes an acid change in the more fermentable articles of food. The acid thus generated partially coagulates the mucus, so that this forms a thick coating round the interior of the digestive tube, and also covers the masses of food swallowed. Consequently a proper admixture of food with the gastric juices and other digestive fluids is interfered with, digestion is slow and imperfect, and of the food which is digested only a small part is brought into contact with the absorbent vessels. The child consequently gets thinner and paler. He is uneasy on account of flatulent pains from gases disengaged in the process of fermentation, and irritable on account of the excess of acid with which the system is charged. In bad cases the emaciation may be very great, and although the appetite may be large, the food taken seems to be, and often actually is, nearly useless for pur poses of nutrition. Commonly, however, when the derangement is severe the appetite fails, and great difficulty is found in persuading the child to take any nourishment at all. Parasitic worms, which find in the alkaline mucus a.congenial nidus for development, frequently complicate this de rangement, but it is to the digestive disorder and not to the worms that the symptoms are really due.
Diagnosis.—It is often very difficult to say whether or not a child has got whooping-cough. At the beginning of the catarrhal stage a diagnosis is impossible. At this early period we can only detect the signs of catarrh, and unless the complaint is largely prevalent at the time, or other children in the house are suffering from pertussis, there is absolutely nothing to make us even suspect its existence. Often, towards the end of this stage, the frequency and peculiar violence of the fits of coughing may rouse our suspicions, and if a genuine paroxysm occur, doubt, of course, ceases to be possible. But although fully developed whooping-cough cannot be mis taken, the modified form of cough which is often all that we can detect may be easily misinterpreted. A more or less prolonged cough with a faint whoop from slight laryngeal spasm is not very uncommon in a child suffering from chest complaint, and an abortive pertussis may sometimes give rise to no more characteristic symptoms than these. In making the distinction no arguments drawn from the acuteness of the attack or the early period at which the cough assumed the spasmodic character can be relied upon, for modified pertussis may be as slight and transient as any mere pulmonary catarrh. It is of far greater importance to notice that in a mild form of whooping-cough the general health is good, and that an examination the chest reveals little deviation from the normal state of things ; while a chest affection sufficiently serious to produce an imitation of whooping-cough will injure the general health and modify the physical signs. It is usually in catarrhal pneumonia that this violent prolonged
cough is noticed. In such cases we find the symptoms and physical signs of this disease, and we exclude pertussis by remarking that the cough did not become paroxysmal until the chest disease was well developed. In a case of real pertussis with secondary catarrhal pneumonia, the character istic cough is very much modified immediately the complication begins. Paroxysms of violent cough with some spasm of the larynx are often no ticed in cases of enlargement of the bronchial glands. But here we get other signs of pressure upon the pneumogastric nerve : the breathing is more or less oppressed and the voice is thick and hoarse between the attacks of cough. Besides, the venous radicles of the face, neck, and chest are usually more visible than natural from pressure upon the innominate vein ; there is no expectoration of ropy mucus ; and the disease is not capable of being communicated to other children.
When convulsions occur in a case of whooping-cough it is very impor tant, with a view to prognosis, to ascertain their mode of origin. If the convulsion is symptomatic of the onset of an inflammatory complication, it is accompanied by a rise of temperature and followed by a diminution in the spasmodic symptoms and a modification of the physical signs in the chest. If it announces the occurrence of collapse of the lung, the charac teristic symptoms which mark that lesion will be present.
If the convulsion arises from exaggeration of the nervous disturbance which is one of the peculiarities of the disease, it will have been preceded by signs of unusual agitation in former fits of coughing. Such seizures are only seen in children known to be nervous, sensitive, and impressionable ; they follow immediately upon the cough, and between the attacks no signs of nervous disturbance remain. So also in the case of convulsions arising from partial asphyxia : the nervous attack is excited by extreme violence of spasm, but after the fit has passed off no signs of cerebral lesion are left behind. If, after a fit, there is squinting, drowsiness, stupor, or other sign of nervous disturbance, we may fear that congestion of brain is present or that thrombosis of the cerebral sinuses has occurred, and should watch the case with grave apprehension.
Prognosis.—Whatever be the age of the child, the prognosis is favour able so long as the disease remains uncomplicated ; but if a complication arise the prospect is less hopeful, and in a very young child any addition to the normal course of the complaint is to be regarded with anxiety. Convulsions, bronchitis with collapse, and catarrhal pneumonia are the principal causes of an unfavourable issue to the disease.