§ 9. Liability to pay compensation; notice of accident. If personal injury by accident arising out of and in the course of the employment is caused to the employee, the employer shall, subject as hereinafter mentioned, be liable to pay compensation under the plan at the rates set out in section ten of this article: provided that the employer shall not be liable in respect of any injury which does not disable the employee for a period of at least two weeks from earning full wages at the work at which he was employed, and that the employer shall not be liable in respect of any injury to the employee which is caused by the serious and willful misconduct of that employee. No proceedings for recovery under the plan provided hereby shall be maintained unless notice of the accident has been given to the employer as soon as practicable after the happening thereof and before the employee has voluntarily left the employment in which he was injured and during such disability, and unless claim for compensation with respect to the accident has been made within six months from the occurrence of the accident, or in the case of death of the employee, or in the event of his physical or mental incapacity within six months after such death or removal of such physical or mental incapacity, or in event that weekly payments have been made under the plan, within six months after such payments have ceased; but no want of or defect or inaccuracy of a notice shall be a bar to the maintenance of proceedings under the plan unless the employer proves that he is prejudiced by said want, defect or inaccuracy. Notice of the accident shall apprise the employer of the claim for compensation under this plan and shall state the name and address of the employee injured, the date and place of the accident and in simple language the cause thereof. The notice may be served personally or by sending it by mail in a registered letter addressed to the employer at his last known residence or place of business.