MENTAL DEVELOPMENT 463 



colouring matter — haemoglobin. Not only may an impoverished 

 blood deficient in red blood corpuscles and other essential 

 constituents be the cause of a mental functional deficiency 

 by depriving the nervous elements of their capacity to grow, 

 develop, store, and liberate energy, but a poisoned condition 

 of the blood is a far more frequent cause of acquired failure 

 of mental energy in infants and children as well as in adults. 

 Such impoverished and poisoned conditions of the blood in 

 infancy arise in a large majority of cases from gastro-intestinal 

 disturbances owing to improper feeding, and may, if con- 

 tinuous, interfere with bodily nutrition and brain development. 

 The intelligent mother accepts such warnings as fits of 

 screaming, restless sleep, crying without obvious cause, refusal 

 of food, and convulsions ; she does not think the infant exhibits 

 these symptoms from temper, but as an evidence of suffering 

 requiring maternal sympathy and protection, and she seeks the 

 cause in order to remove it. Now, imperfect nutrition and 

 poisoned conditions of the blood brought about by fermentation 

 and putrefaction in the gastro-intestinal canal from improper 

 feeding, and from acquired or inherited disease, may not 

 actually arrest the growth of the neurones of the brain any 

 more than they very materially interfere with the growth of 

 the child, and cause arrest of development ; but such unfavour- 

 able conditions of nutrition at the time when the brain is 

 undergoing its most active development cannot but be harmful. 

 I told you in my first lecture that during the first three years 

 after birth the greatest increase in the weight of the brain 

 occurred, and that at three years old it had trebled its weight 

 at birth. Even if with an unfavourable bodily nutrition of the 

 infant the brain grows and develops to nearly treble its weight 

 at the end of three years, we cannot therefore assume that it 

 has in no way suffered from mal-nutrition, any more than we 

 can assume that because a child has grown in stature a few 

 inches less than a well-nourished child, it has not seriously 

 suffered. You naturally ask : How then has the brain suffered ? 

 It has suffered constitutionally, as the child has suffered con- 

 stitutionally ; it is less able to resist the effects of stress from 

 any cause ; it is more liable to exhibit signs of nervous 

 irritability, convulsions of teething, and if the child is infected 

 by the micro-organisms of pneumonia, tubercle, whooping- 

 cough, measles, or scarlet fever, the brain as well as other 



