§ 45. Notice to employers. The employer to whom notice of death or disability is to be given, or against whom claim is to be made by the employee, shall be the employer who last employed the employee in the employment to the nature of which the disease was due and such notice and claim shall be deemed seasonable as against prior employers. The requirements as to notice as to occupational disease and death resulting therefrom shall be the same as required in section eighteen of this chapter, except that the notice shall be given to the employer within two years after the disablement or after the claimant knew or should have known that the disease is due to the nature of the employment, whichever is the later date.